sdrangel/plugins/channelrx/demoddatv/leansdr/dvbs2.h

///////////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2019-2023 Edouard Griffiths, F4EXB <f4exb06@gmail.com>              //
// Copyright (C) 2019 Davide Gerhard <rainbow@irh.it>                                //
// Copyright (C) 2022 Jon Beniston, M7RCE <jon@beniston.com>                         //
//                                                                                   //
// This file is part of LeanSDR Copyright (C) 2016-2019 <pabr@pabr.org>.             //
//                                                                                   //
// This program is free software; you can redistribute it and/or modify              //
// it under the terms of the GNU General Public License as published by              //
// the Free Software Foundation as version 3 of the License, or                      //
// (at your option) any later version.                                               //
//                                                                                   //
// This program is distributed in the hope that it will be useful,                   //
// but WITHOUT ANY WARRANTY; without even the implied warranty of                    //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                      //
// GNU General Public License V3 for more details.                                   //
//                                                                                   //
// You should have received a copy of the GNU General Public License                 //
// along with this program. If not, see <http://www.gnu.org/licenses/>.              //
///////////////////////////////////////////////////////////////////////////////////////

// Latest updates:
//   |  S2: Revert to tracking all symbols. pabr committed on Mar 6, 2019
//   |  Cleanup: Remove debug code. pabr committed on Mar 6, 2019
//   |  S2: Dummy PLFRAME handling pabr committed on Mar 26, 2019
//   |  S2: Preliminary support for GSE pabr committed on Mar 26, 2019
//   |  leandvbtx: Signal S2 MATYPE as TS. pabr committed on Mar 26, 2019
//   |  DVB-S2 VCM support, suitable for ACM reception (not MIS). pabr committed on Nov 24, 2019
//   |  Remove unused constants. pabr committed on Dec 4, 2019
//   |  S2 RX: Capture TED decision history in sampler_state. pabr committed on Dec 5, 2019
//   |  S2 RX: Print error rate on PLS symbols. pabr committed on Dec 5, 2019
//   |  New DVB-S2 receiver with PL-based carrier recovery. modcod/framesize filtering for VCM. pabr committed on Jan 9, 2020
// skip Soft-decoding of S2 PLSCODE. pabr committed on Jan 16, 2020
// skip Validate PLHEADER soft-decoding when DEBUG_CARRIER==1. pabr committed on Jan 17, 2020
//   |  Cleanup scope of some S2 constants. pabr committed on Apr 29, 2020
// skip Fix overflow to state_out stream. pabr committed on Apr 29, 2020
//   |  S2 deframer: Set TEI bit on TS packets with bad CRC8. pabr committed on Jul 29, 2020

#ifndef LEANSDR_DVBS2_H
#define LEANSDR_DVBS2_H

/*
#include "leansdr/bch.h"
#include "leansdr/crc.h"
#include "leansdr/dvb.h"
#include "leansdr/ldpc.h"
#include "leansdr/sdr.h"
#include "leansdr/softword.h"
*/

#include <stdlib.h>
#include <deque>
#include <bitset>

#include "bch.h"
#include "crc.h"
#include "dvb.h"
#include "softword.h"
#include "ldpc.h"
#include "sdr.h"

#include <signal.h>
#ifdef LINUX
#include <sys/wait.h>
#endif
#ifdef _MSC_VER
#include <BaseTsd.h>
typedef SSIZE_T ssize_t;
#endif
#include "ldpctool/layered_decoder.h"
#include "ldpctool/testbench.h"
#include "ldpctool/algorithms.h"
#include "ldpctool/ldpcworker.h"

namespace leansdr
{

// S2 THRESHOLDS (for comparing demodulators)

static const uint32_t S2_MAX_ERR_SOF = 13;        // 26 bits
static const uint64_t S2_MAX_ERR_PLSCODE = 8;     // 64 bits, dmin=32

static const int pilot_length = 36;

// S2 SOF
// EN 302 307-1 section 5.5.2.1 SOF field

template <typename T>
struct s2_sof
{
    static const uint32_t VALUE = 0x18d2e82;
    static const uint32_t MASK = 0x3ffffff;
    static const int LENGTH = 26;
    std::complex<T> symbols[LENGTH];

    s2_sof()
    {
        for (int s = 0; s < LENGTH; ++s)
        {
            int angle = ((VALUE >> (LENGTH - 1 - s)) & 1) * 2 + (s & 1); // pi/2-BPSK
            symbols[s].real(cstln_amp * cosf(M_PI / 4 + 2 * M_PI * angle / 4));
            symbols[s].imag(cstln_amp * sinf(M_PI / 4 + 2 * M_PI * angle / 4));
        }
    }
}; // s2_sof

// S2 PLS CODES
// Precomputes the PLS code sequences.
// EN 302 307-1 section 5.5.2.4 PLS code

template <typename T>
struct s2_plscodes
{
    // PLS index format MODCOD[4:0]|SHORTFRAME|PILOTS
    static const int COUNT = 128;
    static const int LENGTH = 64;
    uint64_t codewords[COUNT];
    std::complex<T> symbols[COUNT][LENGTH];

    s2_plscodes()
    {
        uint32_t G[6] = {0x55555555,
                         0x33333333,
                         0x0f0f0f0f,
                         0x00ff00ff,
                         0x0000ffff,
                         0xffffffff};

        for (int index = 0; index < COUNT; ++index)
        {
            uint32_t y = 0;

            for (int row = 0; row < 6; ++row)
            {
                if ((index >> (6 - row)) & 1) {
                    y ^= G[row];
                }
            }

            uint64_t code = 0;

            for (int bit = 31; bit >= 0; --bit)
            {
                int yi = (y >> bit) & 1;

                if (index & 1) {
                    code = (code << 2) | (yi << 1) | (yi ^ 1);
                } else {
                    code = (code << 2) | (yi << 1) | yi;
                }
            }
            // Scrambling
            code ^= SCRAMBLING;
            // Store precomputed codeword.
            codewords[index] = code;
            // Also store as symbols.

            for (int i = 0; i < LENGTH; ++i)
            {
                int yi = (code >> (LENGTH - 1 - i)) & 1;
                int nyi = yi ^ (i & 1);
                symbols[index][i].real(cstln_amp * (1 - 2 * nyi) / sqrtf(2));
                symbols[index][i].imag(cstln_amp * (1 - 2 * yi) / sqrtf(2));
            }
        }
    }
    static const uint64_t SCRAMBLING = 0x719d83c953422dfa;
}; // s2_plscodes

static const int PILOT_LENGTH = 36;

// Date about pilots.
// Mostly for consistency with s2_sof and s2_plscodes.

template<typename T>
struct s2_pilot
{
    static const int LENGTH = PILOT_LENGTH;
    std::complex<T> symbol;

    s2_pilot()
    {
        symbol.real(cstln_amp*0.707107);
        symbol.imag(cstln_amp*0.707107);
    }
};  // s2_pilot

// S2 SCRAMBLING
// Precomputes the symbol rotations for PL scrambling.
// EN 302 307-1 section 5.5.4 Physical layer scrambling

struct s2_scrambling
{
    uint8_t Rn[131072]; // 0..3  (* 2pi/4)

    s2_scrambling(int codenum = 0)
    {
        uint32_t stx = 0x00001, sty = 0x3ffff;

        // x starts at codenum, wraps at index 2^18-1 by design
        for (int i = 0; i < codenum; ++i) {
            stx = lfsr_x(stx);
        }

        // First half of sequence is LSB of scrambling angle
        for (int i = 0; i < 131072; ++i)
        {
            int zn = (stx ^ sty) & 1;
            Rn[i] = zn;
            stx = lfsr_x(stx);
            sty = lfsr_y(sty);
        }

        // Second half is MSB
        for (int i = 0; i < 131072; ++i)
        {
            int zn = (stx ^ sty) & 1;
            Rn[i] |= zn << 1;
            stx = lfsr_x(stx);
            sty = lfsr_y(sty);
        }
    }

    uint32_t lfsr_x(uint32_t X)
    {
        int bit = ((X >> 7) ^ X) & 1;
        return ((bit << 18) | X) >> 1;
    }

    uint32_t lfsr_y(uint32_t Y)
    {
        int bit = ((Y >> 10) ^ (Y >> 7) ^ (Y >> 5) ^ Y) & 1;
        return ((bit << 18) | Y) >> 1;
    }
}; // s2_scrambling

// S2 BBSCRAMBLING
// Precomputes the xor pattern for baseband scrambling.
// EN 302 307-1 section 5.2.2 BB scrambling

struct s2_bbscrambling
{
    s2_bbscrambling()
    {
        uint16_t st = 0x00a9; // 000 0000 1010 1001  (Fig 5 reversed)

        for (unsigned int i = 0; i < sizeof(pattern); ++i)
        {
            uint8_t out = 0;

            for (int n = 8; n--;)
            {
                int bit = ((st >> 13) ^ (st >> 14)) & 1; // Taps
                out = (out << 1) | bit;                  // MSB first
                st = (st << 1) | bit;                    // Feedback
            }

            pattern[i] = out;
        }
    }

    void transform(const uint8_t *in, int bbsize, uint8_t *out)
    {
        for (int i = 0; i < bbsize; ++i) {
            out[i] = in[i] ^ pattern[i];
        }
    }

  private:
    uint8_t pattern[58192]; // Values 0..3
}; // s2_bbscrambling

// S2 PHYSICAL LAYER SIGNALLING

struct s2_pls
{
    int modcod; // 0..31
    bool sf;
    bool pilots;

    int framebits() const {
        return sf ? 16200 : 64800;
    }

    bool is_dummy() {
        return (modcod==0);
    }
};

static const int PLSLOT_LENGTH = 90;

template <typename SOFTSYMB>
struct plslot
{
    static const int LENGTH = PLSLOT_LENGTH;
    bool is_pls;
    union {
        s2_pls pls;
        SOFTSYMB symbols[LENGTH];
    };
};

// EN 302 307-1 section 5.5.2.2 MODCOD field
// EN 302 307-1 section 6 Error performance

const struct modcod_info
{
    static const int MIN_SLOTS_PER_FRAME = 144;
    static const int MIN_SYMBOLS_PER_FRAME =
        (1+MIN_SLOTS_PER_FRAME) * PLSLOT_LENGTH;
    static const int MAX_SLOTS_PER_FRAME = 360;
    static const int MAX_SYMBOLS_PER_FRAME =
        (1 + MAX_SLOTS_PER_FRAME) * PLSLOT_LENGTH +
        ((MAX_SLOTS_PER_FRAME - 1) / 16) * PILOT_LENGTH;
    int nslots_nf; // Number of 90-symbol slots per normal frame
    int nsymbols;  // Symbols in the constellation
    cstln_base::predef c;
    code_rate rate;
    // Ideal Es/N0 for normal frames
    // EN 302 307 section 6 Error performance
    float esn0_nf;
    // Radii for APSK
    // EN 302 307, section 5.4.3, Table 9
    // EN 302 307, section 5.4.4, Table 10
    float g1, g2, g3;
} modcod_infos[32] = {
    {0, 0, cstln_base::BPSK, FEC12, 0.0, 0.0, 0.0, 0.0},
    // 1 - 11
    {360, 4, cstln_base::QPSK, FEC14, -2.35, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC13, -1.24, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC25, -0.30, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC12, 1.00, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC35, 2.23, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC23, 3.10, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC34, 4.03, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC45, 4.68, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC56, 5.18, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC89, 6.20, 0.0, 0.0, 0.0},
    {360, 4, cstln_base::QPSK, FEC910, 6.42, 0.0, 0.0, 0.0},
    // 12 - 17
    {240, 8, cstln_base::PSK8, FEC35, 5.50, 0.0, 0.0, 0.0},
    {240, 8, cstln_base::PSK8, FEC23, 6.62, 0.0, 0.0, 0.0},
    {240, 8, cstln_base::PSK8, FEC34, 7.91, 0.0, 0.0, 0.0},
    {240, 8, cstln_base::PSK8, FEC56, 9.35, 0.0, 0.0, 0.0},
    {240, 8, cstln_base::PSK8, FEC89, 10.69, 0.0, 0.0, 0.0},
    {240, 8, cstln_base::PSK8, FEC910, 10.98, 0.0, 0.0, 0.0},
    // 18 - 23
    {180, 16, cstln_base::APSK16, FEC23, 8.97, 3.15, 0.0, 0.0},
    {180, 16, cstln_base::APSK16, FEC34, 10.21, 2.85, 0.0, 0.0},
    {180, 16, cstln_base::APSK16, FEC45, 11.03, 2.75, 0.0, 0.0},
    {180, 16, cstln_base::APSK16, FEC56, 11.61, 2.70, 0.0, 0.0},
    {180, 16, cstln_base::APSK16, FEC89, 12.89, 2.60, 0.0, 0.0},
    {180, 16, cstln_base::APSK16, FEC910, 13.13, 2.57, 0.0, 0.0},
    // 24 - 28
    {144, 32, cstln_base::APSK32, FEC34, 12.73, 2.84, 5.27, 0.0},
    {144, 32, cstln_base::APSK32, FEC45, 13.64, 2.72, 4.87, 0.0},
    {144, 32, cstln_base::APSK32, FEC56, 14.28, 2.64, 4.64, 0.0},
    {144, 32, cstln_base::APSK32, FEC89, 15.69, 2.54, 4.33, 0.0},
    {144, 32, cstln_base::APSK32, FEC910, 16.05, 2.53, 4.30, 0.0},
    // 29 - 31
    {0, 0, cstln_base::BPSK, FEC12, 0.0, 0.0, 0.0, 0.0},
    {0, 0, cstln_base::BPSK, FEC12, 0.0, 0.0, 0.0, 0.0},
    {0, 0, cstln_base::BPSK, FEC12, 0.0, 0.0, 0.0, 0.0}
};

// Assert that a MODCOD number is valid
const modcod_info *check_modcod(int m)
{
    if (m < 0 || m > 31) {
        fail("Invalid MODCOD number");
    }

    const modcod_info *r = &modcod_infos[m];

    if (!r->nslots_nf) {
        fail("Unsupported MODCOD");
    }

    return r;
}

// S2 FRAME TRANSMITTER

template <typename T>
struct s2_frame_transmitter : runnable
{
    s2_frame_transmitter(
        scheduler *sch,
        pipebuf<plslot<hard_ss>> &_in,
        pipebuf<std::complex<T>> &_out
    ) :
        runnable(sch, "S2 frame transmitter"),
        in(_in),
        out(_out, modcod_info::MAX_SYMBOLS_PER_FRAME)
    {
        float amp = cstln_amp / sqrtf(2);
        qsymbols[0].real() = +amp;
        qsymbols[0].imag() = +amp;
        qsymbols[1].real() = +amp;
        qsymbols[1].imag() = -amp;
        qsymbols[2].real() = -amp;
        qsymbols[2].imag() = +amp;
        qsymbols[3].real() = -amp;
        qsymbols[3].imag() = -amp;

        // Clear the constellation cache.
        for (int i = 0; i < 32; ++i) {
            pcsymbols[i] = nullptr;
        }
    }

    ~s2_frame_transmitter()
    {
    }

    void run()
    {
        while (in.readable() >= 1)
        {
            plslot<hard_ss> *pin = in.rd();

            if (!pin->is_pls) {
                fail("Expected PLS pseudo-slot");
            }

            s2_pls *pls = &pin->pls;
            const modcod_info *mcinfo = check_modcod(pls->modcod);
            int nslots = (pls->sf ? mcinfo->nslots_nf / 4 : mcinfo->nslots_nf);

            if (in.readable() < 1 + nslots) {
                break;
            }

            // Require room for BBHEADER + slots + optional pilots.
            int nsymbols = ((1 + nslots) * plslot<hard_ss>::LENGTH +
                            (pls->pilots ? ((nslots - 1) / 16) * pilot_length : 0));

            if (out.writable() < nsymbols) {
                break;
            }

            int nw = run_frame(pls, mcinfo, pin + 1, nslots, out.wr());

            if (nw != nsymbols) {
                fail("Bug: s2_frame_transmitter overflow");
            }

            in.read(1 + nslots);
            out.written(nsymbols);
        }
    }

    int run_frame(
        s2_pls *pls,
        const modcod_info *mcinfo,
        const plslot<hard_ss> *pin,
        int nslots,
        std::complex<T> *pout
    )
    {
        (void)mcinfo;
        
        std::complex<T> *pout0 = pout; // For sanity check
        // PLHEADER: SOF AND PLSCODE
        // EN 302 307-1 section 5.5.2 PL signalling
        memcpy(pout, sof.symbols, sof.LENGTH * sizeof(*pout));
        pout += sof.LENGTH;
        int pls_index = (pls->modcod << 2) | (pls->sf << 1) | pls->pilots;
        memcpy(pout, plscodes.symbols[pls_index], plscodes.LENGTH * sizeof(*pout));
        pout += plscodes.LENGTH;
        std::complex<T> *csymbols = get_csymbols(pls->modcod);
        // Slots and pilots
        int till_next_pilot = pls->pilots ? 16 : nslots;
        uint8_t *scr = &scrambling.Rn[0];

        for (int S = 0; S < nslots; ++S, ++pin, --till_next_pilot)
        {
            if (till_next_pilot == 0)
            {
                // Send pilot
                for (int s = 0; s < pilot_length; ++s, ++scr, ++pout) {
                    scramble(&qsymbols[0], *scr, pout);
                }
                till_next_pilot = 16;
            }

            // Send slot
            if (pin->is_pls) {
                fail("s2_frame_transmitter: bad input sequence");
            }

            const hard_ss *ps = pin->symbols;

            for (int s = 0; s < pin->LENGTH; ++s, ++ps, ++scr, ++pout) {
                scramble(&csymbols[*ps], *scr, pout);
            }
        }

        return pout - pout0;
    }

    inline void scramble(const std::complex<T> *src, uint8_t r, std::complex<T> *dst)
    {
        switch (r)
        {
        case 3:
            dst->re = src->im;
            dst->im = -src->re;
            break;
        case 2:
            dst->re = -src->re;
            dst->im = -src->im;
            break;
        case 1:
            dst->re = -src->im;
            dst->im = src->re;
            break;
        default:
            *dst = *src;
        }
    }

  private:
    pipereader<plslot<hard_ss>> in;
    pipewriter<std::complex<T>> out;
    std::complex<T> *pcsymbols[32];  // Constellations in use, indexed by modcod

    std::complex<T> *get_csymbols(int modcod)
    {
        if (!pcsymbols[modcod])
        {
            const modcod_info *mcinfo = check_modcod(modcod);

            if (sch->debug)
            {
                fprintf(
                    stderr,
                    "Building constellation %s ratecode %d\n",
                    cstln_base::names[mcinfo->c],
                    mcinfo->rate
                );
            }

            // TBD Different Es/N0 for short frames ?
            cstln_lut<hard_ss,256> cstln(
                mcinfo->c,
                mcinfo->esn0_nf,
                mcinfo->g1,
                mcinfo->g2,
                mcinfo->g3
            );

            pcsymbols[modcod] = new std::complex<T>[cstln.nsymbols];

            for ( int s=0; s<cstln.nsymbols; ++s )
            {
                pcsymbols[modcod][s].real() = cstln.symbols[s].real();
                pcsymbols[modcod][s].imag() = cstln.symbols[s].imag();
            }
        }

        return pcsymbols[modcod];
    }

    std::complex<T> qsymbols[4]; // RMS cstln_amp
    s2_sof<T> sof;
    s2_plscodes<T> plscodes;
    s2_scrambling scrambling;
}; // s2_frame_transmitter

// S2 FRAME RECEIVER

#define TEST_DIVERSITY 0

template<typename T, typename SOFTSYMB>
struct s2_frame_receiver : runnable
{
    sampler_interface<T> *sampler;
    int meas_decimation;
    float Ftune;         // Tuning bias in cycles per symbol
    bool allow_drift;    // Unbounded carrier tracking
    float omega0;        // Samples per symbol
    bool strongpls;      // PL symbols at max amplitude (default: RMS)
    uint32_t modcods;    // Bitmask of desired modcods
    uint8_t framesizes;  // Bitmask of desired frame sizes
    bool fastlock;       // Synchronize more aggressively
    bool fastdrift;      // Carrier drift faster than pilots
    float freq_tol;      // Tolerance on carrier frequency
    float sr_tol;        // Tolerance on symbol rate

    s2_frame_receiver(
        scheduler *sch,
        sampler_interface<T> *_sampler,
        pipebuf< std::complex<T> > &_in,
        pipebuf< plslot<SOFTSYMB> > &_out,
        pipebuf<float> *_freq_out=NULL,
        pipebuf<float> *_ss_out=NULL,
        pipebuf<float> *_mer_out=NULL,
        pipebuf< std::complex<float> > *_cstln_out=NULL,
        pipebuf< std::complex<float> > *_cstln_pls_out=NULL,
        pipebuf< std::complex<float> > *_symbols_out=NULL,
        pipebuf<int> *_state_out=NULL
    ) :
        runnable(sch, "S2 frame receiver"),
        sampler(_sampler),
        meas_decimation(1048576),
        Ftune(0),
        allow_drift(false),
        strongpls(false),
        modcods(0xffffffff),
        framesizes(0x03),
        fastlock(false),
        fastdrift(false),
        freq_tol(0.25),
        sr_tol(100e-6),
        cstln(NULL),
        in(_in), out(_out,1+modcod_info::MAX_SLOTS_PER_FRAME),
        meas_count(0),
        freq_out(opt_writer(_freq_out)),
        ss_out(opt_writer(_ss_out)),
        mer_out(opt_writer(_mer_out)),
        cstln_out(opt_writer(_cstln_out,1024)),
        cstln_pls_out(opt_writer(_cstln_pls_out,1024)),
        symbols_out(opt_writer(_symbols_out, modcod_info::MAX_SYMBOLS_PER_FRAME)),
        state_out(opt_writer(_state_out)),
        first_run(true),
        scrambling(0),
        pls_total_errors(0),
        pls_total_count(0),
        m_modcodType(-1),
        m_modcodRate(-1),
        m_locked(false),
        diffs(nullptr),
        sspilots(nullptr)
    {
        // Constellation for PLS
        qpsk = new cstln_lut<SOFTSYMB,256>(cstln_base::QPSK);

        // Clear the constellation cache.
        for (int i=0; i<32; ++i) {
            cstlns[i] = NULL;
        }

#if TEST_DIVERSITY
        fprintf(stderr, "** DEBUG: Diversity test mode (slower)\n");
#endif
    }

    ~s2_frame_receiver()
    {
        delete qpsk;

        for (int i=0; i<32; ++i)
        {
            if (cstlns[i]) {
                delete cstlns[i];
            }
        }

        if (diffs) {
            delete[] diffs;
        }

        if (sspilots) {
            delete[] sspilots;
        }
    }

    enum {
      FRAME_DETECT,   // Looking for PLHEADER
      FRAME_PROBE,    // Aligned with PLHEADER, ready to recover carrier
      FRAME_LOCKED,   // Demodulating
    } state;

    // sampler_state holds the entire state of the PLL.
    // Useful for looking ahead (e.g. next pilots/SOF) then rewinding.

    struct sampler_state {
        std::complex<T> *p;  // Pointer to samples (update when entering run())
        float mu;       // Time of next symbol, counted from p
        float omega;    // Samples per symbol
        float gain;     // Scaling factor toward cstln_amp
        float ph16;     // Carrier phase at next symbol (cycles * 65536)
        float fw16;     // Carrier frequency (cycles per symbol * 65536)
        uint8_t *scr;   // Position in scrambling sequence for next symbol

        void normalize() {
            ph16 = fmodf(ph16, 65536.0f);  // Rounding direction irrelevant
        }

        void skip_symbols(int ns)
        {
            mu += omega * ns;
            p += (int)floorf(mu);
            mu -= floorf(mu);
            ph16 += fw16 * ns;
            normalize();
            scr += ns;
        }

        char *format() {
            static char buf[256];
            sprintf(
                buf,
                "%9.2lf %+6.0f ppm  %+3.0f °  %f",
                (double)((p-(std::complex<T>*)NULL)&262143)+mu,  // Arbitrary wrap
                fw16*1e6/65536,
                fmodfs(ph16,65536.0f)*360/65536,
                gain
            );
            return buf;
        }
    };

    float min_freqw16, max_freqw16;

    // State during FRAME_SEARCH and FRAME_LOCKED
    sampler_state ss_cache;

    void run()
    {
        if (strongpls) {
            fail("--strongpls is broken.");
        }

        // Require enough samples to detect one plheader,
        // TBD margin ?
        int min_samples = (1 + modcod_info::MAX_SYMBOLS_PER_FRAME +
        sof.LENGTH+plscodes.LENGTH)*omega0 * 2;

        while (in.readable() >= min_samples + sampler->readahead() &&
            out.writable() >= 1+modcod_info::MAX_SLOTS_PER_FRAME &&
            opt_writable(freq_out, 1) &&
            opt_writable(ss_out, 1) &&
            opt_writable(mer_out, 1) &&
            opt_writable(symbols_out, modcod_info::MAX_SYMBOLS_PER_FRAME) &&
            opt_writable(state_out, 1))
        {
            if (first_run)
            {
                enter_frame_detect();
                first_run = false;
            }

            switch ( state )
            {
            case FRAME_DETECT:
                run_frame_detect();
                break;
            case FRAME_PROBE:
                run_frame_probe();
                break;
            case FRAME_LOCKED:
                run_frame_locked();
                break;
            }
        }
    }

    // State transition
    void enter_frame_detect()
    {
        state = FRAME_DETECT;
        // Setup sampler for interpolation only.
        ss_cache.fw16 = 65536 * Ftune;
        ss_cache.ph16 = 0;
        ss_cache.mu = 0;
        ss_cache.gain = 1;
        ss_cache.omega = omega0;

        // Set frequency tracking boundaries around tuning frequency.
        if (allow_drift)
        {
            // Track across the whole baseband.
            min_freqw16 = ss_cache.fw16 - omega0*65536;
            max_freqw16 = ss_cache.fw16 + omega0*65536;
        }
        else
        {
            min_freqw16 = ss_cache.fw16 - freq_tol*65536.0;
            max_freqw16 = ss_cache.fw16 + freq_tol*65536.0;
        }

        opt_write(state_out, 0);

        if (sch->debug) {
            fprintf(stderr, "enter_frame_detect\n");
        }

        if (fastlock || first_run)
        {
            discard = 0;
        }
        else
        {
            // Discard some data so that CPU usage during PLHEADER detection
            // is at same level as during steady-state demodulation.
            // This has no effect if the first detection is successful.
            float duty_factor = 5;
            discard = modcod_info::MAX_SYMBOLS_PER_FRAME * omega0 * (duty_factor+rand_compat()-0.5);
        }
    }

    long discard;

    void run_frame_detect()
    {
        cstln->m_rateCode = -1;
        cstln->m_typeCode = -1;
        cstln->m_setByModcod = cstln->m_typeCode != -1;

        if (discard)
        {
            size_t d = std::min(discard, in.readable());
            in.read(d);
            discard -= d;
            return;
        }

        sampler->update_freq(ss_cache.fw16/omega0);

        const int search_range = modcod_info::MAX_SYMBOLS_PER_FRAME;
        ss_cache.p = in.rd();
        find_plheader(&ss_cache, search_range);
#if DEBUG_CARRIER
        fprintf(stderr, "CARRIER diffcorr: %.0f%%  %s\n",
            q*100, ss_cache.format());
#endif
        in.read(ss_cache.p-in.rd());
        enter_frame_probe();
    }

    void enter_frame_probe()
    {
        if (sch->debug) {
            fprintf(stderr, "PROBE\n");
        }

        if (m_locked)
        {
            fprintf(stderr, "UNLOCKED\n");
            m_locked = false;
        }

        state = FRAME_PROBE;
    }

    void run_frame_probe() {
      return run_frame_probe_locked();
    }

    void enter_frame_locked()
    {
        state = FRAME_LOCKED;

        if (sch->debug) {
            fprintf(stderr, "LOCKED\n");
        }

        if (!m_locked)
        {
            fprintf(stderr, "LOCKED\n");
            m_locked = true;
        }

        opt_write(state_out, 1);
    }

    void run_frame_locked() {
        return run_frame_probe_locked();
    }

    // Process one frame.
    // Perform additional carrier estimation if state==FRAME_PROBE.

    void run_frame_probe_locked()
    {
        std::complex<float> *psampled;  // Data symbols (one per slot)

        if (cstln_out && cstln_out->writable()>=1024) {
            psampled = cstln_out->wr();
        } else {
            psampled = NULL;
        }

        std::complex<float> *psampled_pls;  // PLHEADER symbols

        if (cstln_pls_out && cstln_pls_out->writable()>=1024) {
            psampled_pls = cstln_pls_out->wr();
        } else {
            psampled_pls = NULL;
        }
#if TEST_DIVERSITY
        std::complex<float> *psymbols = symbols_out ? symbols_out->wr() : NULL;
        float scale_symbols = 1.0 / cstln_amp;
#endif
        sampler_state ss = ss_cache;
        ss.p = in.rd();
        ss.normalize();
        sampler->update_freq(ss.fw16/omega0);
#if DEBUG_CARRIER
        fprintf(stderr, "CARRIER frame: %s\n", ss.format());
#endif
        // Interpolate PLHEADER.

        const int PLH_LENGTH = sof.LENGTH + plscodes.LENGTH;
        std::complex<float> plh_symbols[PLH_LENGTH];

        for (int s=0; s<PLH_LENGTH; ++s)
        {
            std::complex<float> p = interp_next(&ss) * ss.gain;
            plh_symbols[s] = p;

            if (psampled_pls) {
                *psampled_pls++ = p;
            }
        }

        // Decode SOF.

        uint32_t sof_bits = 0;

        // Optimization with half loop and even/odd processing in a single step
        for (int i = 0; i < sof.LENGTH/2; ++i)
        {
            std::complex<float> p0 = plh_symbols[2*i];
            std::complex<float> p1 = plh_symbols[2*i+1];
            float d0 = p0.imag() + p0.real();
            float d1 = p1.imag() - p1.real();
            sof_bits = (sof_bits<<2) | ((d0<0)<<1) | (d1<0);
        }

        uint32_t sof_errors = hamming_weight(sof_bits ^ sof.VALUE);
        pls_total_errors += sof_errors;
        pls_total_count += sof.LENGTH;

        if (sof_errors >= S2_MAX_ERR_SOF)
        {
            if (sch->debug2) {
                fprintf(stderr, "Too many errors in SOF (%u/%u)\n", sof_errors, S2_MAX_ERR_SOF);
            }

            in.read(ss.p-in.rd());
            enter_frame_detect();
            return;
        }

        // Decode PLSCODE.

        uint64_t plscode = 0;

        // Optimization with half loop and even/odd processing in a single step
        for (int i=0; i<plscodes.LENGTH/2; ++i)
        {
            std::complex<float> p0 = plh_symbols[sof.LENGTH+2*i];
            std::complex<float> p1 = plh_symbols[sof.LENGTH+2*i+1];
            float d0 = p0.imag() + p0.real();
            float d1 = p1.imag() - p1.real();
            plscode = (plscode<<2) | ((d0<0)<<1) | (d1<0);
        }

        uint32_t plscode_errors = plscodes.LENGTH + 1;
        int plscode_index = -1;  // Avoid compiler warning.

        // TBD: Optimization?
#if 1
        for (int i = 0; i < plscodes.COUNT; ++i)
        {
            // number of different bits from codeword
            uint32_t e = std::bitset<64>(plscode ^ plscodes.codewords[i]).count();

            if (e < plscode_errors )
            {
                plscode_errors = e;
                plscode_index = i;
            }
        }
#else
        uint64_t pls_candidates[plscodes.COUNT];
        std::fill(pls_candidates, pls_candidates + plscodes.COUNT, plscode);
        std::transform(pls_candidates, pls_candidates + plscodes.COUNT, plscodes.codewords, pls_candidates, [](uint64_t x, uint64_t y) {
            return hamming_weight(x^y); // number of different bits with codeword
        });
        uint64_t *pls_elected = std::min_element(pls_candidates, pls_candidates + plscodes.COUNT); // choose the one with lowest difference
        plscode_errors = *pls_elected;
        plscode_index = pls_elected - pls_candidates;
#endif
        pls_total_errors += plscode_errors;
        pls_total_count += plscodes.LENGTH;

        if (plscode_errors >= S2_MAX_ERR_PLSCODE)
        {
            if (sch->debug2) {
                fprintf(stderr, "Too many errors in plscode (%u/%lu)\n", plscode_errors, S2_MAX_ERR_PLSCODE);
            }

            in.read(ss.p-in.rd());
            enter_frame_detect();
            return;
        }

        // ss now points to first data slot.
        ss.scr = scrambling.Rn;

        std::complex<float> plh_expected[PLH_LENGTH];

        std::copy(sof.symbols, sof.symbols + sof.LENGTH, plh_expected);
        std::copy(plscodes.symbols[plscode_index], plscodes.symbols[plscode_index] + plscodes.LENGTH, &plh_expected[sof.LENGTH]);

        if ( state == FRAME_PROBE )
        {
	        // Carrier frequency from differential detector is still not reliable.
	        // Use known PLH symbols to improve.
	        match_freq(plh_expected, plh_symbols, PLH_LENGTH, &ss);
#if DEBUG_CARRIER
	        fprintf(stderr, "CARRIER freq: %s\n", ss.format());
#endif
        }

        // Use known PLH symbols to estimate carrier phase and amplitude.

        float mer2 = match_ph_amp(plh_expected, plh_symbols, PLH_LENGTH, &ss);
        float mer = 10*log10f(mer2);
#if DEBUG_CARRIER
        fprintf(stderr, "CARRIER plheader: %s MER %.1f dB\n", ss.format(), mer);
#endif
      // Parse PLSCODE.

        s2_pls pls;
        pls.modcod = plscode_index >> 2;  // Guaranteed 0..31
        pls.sf = plscode_index & 2;
        pls.pilots = plscode_index & 1;

        plslot<SOFTSYMB> *pout=out.wr(), *pout0 = pout;

        if  (sch->debug2)
        {
	        fprintf(
                stderr,
                "PLS: mc=%2d, sf=%d, pilots=%d (%2u/90) %4.1f dB ",
		        pls.modcod,
                pls.sf,
                pls.pilots,
                sof_errors + plscode_errors,
                mer
            );
        }

        // Determine contents of frame.

        int S;                            // Data slots in this frame
        cstln_lut<SOFTSYMB,256> *dcstln;  // Constellation for data slots

        if (pls.is_dummy())
        {
            S = 36;
            dcstln = qpsk;
        }
        else
        {
            const modcod_info *mcinfo = &modcod_infos[pls.modcod];

            if (! mcinfo->nslots_nf)
            {
                fprintf(stderr, "Unsupported or corrupted MODCOD\n");
                in.read(ss.p-in.rd());
                enter_frame_detect();
                return;
            }

            if (mer < mcinfo->esn0_nf - 3.0f) // was -1.0f
            {
                // False positive from PLHEADER detection.
                if (sch->debug) {
                    fprintf(stderr, "Insufficient MER (%f/%f)\n", mer, mcinfo->esn0_nf - 3.0f);
                }

                in.read(ss.p-in.rd());
                enter_frame_detect();
                return;
            }

            if (pls.sf && mcinfo->rate == FEC910)
            {  // TBD use fec_infos
                fprintf(stderr, "Unsupported or corrupted FEC\n");
                in.read(ss.p-in.rd());
                enter_frame_detect();
                return;
            }

            // Store current MODCOD info
            if (mcinfo->c != m_modcodType) {
                m_modcodType = mcinfo->c < cstln_base::predef::COUNT ? mcinfo->c : -1;
            }

            if (mcinfo->rate != m_modcodRate) {
                m_modcodRate = mcinfo->rate < code_rate::FEC_COUNT ? mcinfo->rate : -1;
            }

            S = pls.sf ? mcinfo->nslots_nf/4 : mcinfo->nslots_nf;
            // Constellation for data slots.
            dcstln = get_cstln(pls.modcod);
            cstln = dcstln;  // Used by GUI
            cstln->m_rateCode = mcinfo->rate < code_rate::FEC_COUNT ? mcinfo->rate : -1;
            cstln->m_typeCode = mcinfo->c < cstln_base::predef::COUNT ? mcinfo->c : -1;
            cstln->m_setByModcod = cstln->m_typeCode != -1;
            // Output special slot with PLS information.
            pout->is_pls = true;
            pout->pls = pls;
            ++pout;
        }

        // Now we know the frame structure.
        // Estimate carrier over known symbols.

#if DEBUG_LOOKAHEAD
        static int plh_counter = 0;  // For debugging only
        fprintf(stderr, "\nLOOKAHEAD %d PLH sr %+3.0f  %s  %.1f dB\n",
	        plh_counter, (1-ss.omega/omega0)*1e6,
	        ss.format(), 10*log10f(mer2));
#endif
        // Next SOF
        sampler_state ssnext;

        {
            ssnext = ss;
            int ns = (S*PLSLOT_LENGTH +
                (pls.pilots?((S-1)/16)*pilot.LENGTH:0));
            // Find next SOP at expected position +- tolerance on symbol rate.
            int ns_tol = lrintf(ns*sr_tol);
            ssnext.omega = omega0;
            ssnext.skip_symbols(ns-ns_tol);
            find_plheader(&ssnext, ns_tol*2);
            // Don't trust frequency from differential correlator.
            // Our current estimate should be better.
            ssnext.fw16 = ss.fw16;
            interp_match_sof(&ssnext);
#if DEBUG_CARRIER
            fprintf(stderr, "\nCARRIER next: %.0f%%  %s  %.1f dB\n",
                q*100, ssnext.format(), 10*log10f(m2));
#endif
            // Estimate symbol rate (considered stable over whole frame)
            float dist = (ssnext.p-ss.p) + (ssnext.mu-ss.mu);
            // Set symbol period accordingly.
            ss.omega = dist / (ns+sof.LENGTH);
        }

        // Pilots
        int npilots = (S-1) / 16;

        if (sspilots) {
            delete[] sspilots;
        }

        sspilots = new sampler_state[npilots];

        // Detect pilots
        if (pls.pilots)
        {
            sampler_state ssp = ss;

            for ( int i=0; i<npilots; ++i )
            {
                ssp.skip_symbols(16*PLSLOT_LENGTH);
                interp_match_pilot(&ssp);
                sspilots[i] = ssp;
#if DEBUG_LOOKAHEAD
                fprintf(stderr, "LOOKAHEAD %d PILOT%02d  sr %+3.0f  %s  %.1f dB\n",
                    plh_counter, i, (1-ssp.omega/omega0)*1e6,
                    ssp.format(), 10*log10f(mer2));
#endif
        	}
        }

        if (pls.pilots)
        {
            // Measure average frequency, using pilots to unwrap.
            float totalph = 0;
            float prevph = ss.ph16;
            int span = 16*PLSLOT_LENGTH + pilot.LENGTH;
            // Wrap phase around current freq estimate, pilot by pilot.

            for (int i=0; i<npilots; ++i)
            {
                float dph = sspilots[i].ph16 - (prevph+ss.fw16*span);
                totalph += fmodfs(dph, 65536.0f);
                prevph = sspilots[i].ph16;
            }

            // TBD Use data between last pilot and next SOF ?
            // Tricky when there is still an integer ambiguity.
            ss.fw16 += totalph / (span*npilots);
        }
        else
        {
            // Measure average frequency over whole frame.
            // Mostly useful for null frames.
            int span = S*plslot<SOFTSYMB>::LENGTH + sof.LENGTH;
            float dph = ssnext.ph16 - (ss.ph16+ss.fw16*span);
            ss.fw16 += fmodfs(dph,65536.0f) / span;
        }
#if DEBUG_LOOKAHEAD
        fprintf(stderr, "LOOKAHEAD %d NEXTSOF  sr %+3.0f  %s  %.1f dB\n",
            plh_counter, (1-ssnext.omega/omega0)*1e6,
            ssnext.format(), 10*log10f(mer2));
        ++plh_counter;
#endif

        if (state == FRAME_PROBE)
        {
            float fw0 = ss.fw16;
            match_frame(&ss, &pls, S, dcstln);
            // Apply retroactively from midpoint of pilots and next SOF.
            float fw_adj = ss.fw16 - fw0;

            if (pls.pilots)
            {
                for (int i=0; i<npilots; ++i) {
                    sspilots[i].ph16 += fw_adj * PILOT_LENGTH / 2;
                }
            }

            ssnext.ph16 += fw_adj * sof.LENGTH / 2;
#if DEBUG_CARRIER
        	fprintf(stderr, "CARRIER disambiguated:  %s\n", ss.format());
#endif
        }

        // TBD In FRAME_LOCKED, match_frame with sliprange +-1
        // to avoid broken locks ?

        // Per-frame statistics on carrier frequency.
        // Useful at very low symbol rates to detect situations where
        // the carrier fluctuates too fast for pilot-aided recovery.
        statistics<float> freq_stats;

        // Read slots and pilots
#if DEBUG_CARRIER
        fprintf(stderr, "CARRIER data: %s\n", ss.format());
#endif

        // int pilot_errors = 0;

        for (int slot=0; slot<S; ++slot,++pout)
        {
            // Pilot before this slot ?

            if (pls.pilots && !(slot&15) && slot)
            {
                ss.skip_symbols(pilot.LENGTH);
                ss.ph16 = sspilots[slot/16-1].ph16;
            }

	        // Time for pilot-aided carrier recovery ?
            if ( pls.pilots && !(slot&15) && slot+16<S )
            {
                // Sequence of data slots followed by pilots
                sampler_state *ssp = &sspilots[slot/16];
                int span = 16*pout->LENGTH + pilot.LENGTH;
                float dph = ssp->ph16 - (ss.ph16+ss.fw16*span);
                ss.fw16 += fmodfs(dph,65536.0f) / span;
            }
            else if (( pls.pilots && !(slot&15) && slot+16>=S) ||
                (!pls.pilots && !slot ))
            {
                // Sequence of data slots followed by SOF
                int span = (S-slot)*pout->LENGTH + sof.LENGTH;
                float dph = ssnext.ph16 - (ss.ph16+ss.fw16*span);
                ss.fw16 += fmodfs(dph,65536.0f) / span;
            }

            // Read slot.
            freq_stats.add(ss.fw16);
            pout->is_pls = false;
            std::complex<float> p;  // Export last symbols for cstln_out

        	for (int s=0; s<pout->LENGTH; ++s)
            {
	            p = interp_next(&ss) * ss.gain;
#if TEST_DIVERSITY
                if ( psymbols )
                    *psymbols++ = p * scale_symbols;
#endif
                if (!pls.pilots || fastdrift) {
                    (void) track_symbol(&ss, p, dcstln);  // SLOW
                }

	            std::complex<float> d = descramble(&ss, p);
#if 1  // Slow
	            SOFTSYMB *symb = &dcstln->lookup(d.real(), d.imag())->ss;
#else  // Avoid scaling floats. May wrap at very low SNR.
	            SOFTSYMB *symb = &dcstln->lookup((int)d.real(), (int)d.imag())->ss;
#endif
	            pout->symbols[s] = *symb;
	        }

	        ss.normalize();

            if (psampled) {
                *psampled++ = p;
            }
        }  // slot

        if (sch->debug2)
        {
            fprintf(
                stderr,
                "sr%+.0f fs=%.0f\n",
                (1-ss.omega/omega0)*1e6,
                (freq_stats.max()-freq_stats.min())*1e6/65536.0f
            );
        }

        // Commit whole frame after final SOF.
        if (! pls.is_dummy())
        {
            if ((modcods&(1<<pls.modcod)) && (framesizes&(1<<pls.sf)))
            {
                out.written(pout-pout0);
            }
            else
            {
                if (sch->debug2) {
                    fprintf(stderr, "modcod %d size %d rejected\n", pls.modcod, pls.sf);
                }
            }
        }

        // Write back sampler progress
        meas_count += ss.p - in.rd();
        in.read(ss.p-in.rd());
        ss_cache = ss;

        // Measurements
        if (psampled) {
            cstln_out->written(psampled-cstln_out->wr());
        }

        if (psampled_pls) {
            cstln_pls_out->written(psampled_pls-cstln_pls_out->wr());
        }
#if TEST_DIVERSITY
        if ( psymbols ) symbols_out->written(psymbols-symbols_out->wr());
#endif
        if (meas_count >= meas_decimation)
        {
            opt_write(freq_out, ss_cache.fw16/65536/ss_cache.omega);
            opt_write(ss_out, cstln_amp / ss_cache.gain);
            opt_write(mer_out, mer2 ? 10*log10f(mer2) : -99);
            meas_count -= meas_decimation;
        }

        if (state == FRAME_PROBE)
        {
	        // First frame completed successfully.  Validate the lock.
	        enter_frame_locked();
        }

        if (ss_cache.fw16<min_freqw16 || ss_cache.fw16>max_freqw16)
        {
            fprintf(stderr, "Carrier out of bounds\n");
            enter_frame_detect();
        }
    } // run_frame_probe_locked

    // Find most likely PLHEADER between *pss and *pss+search_range
    // by differential correlation.
    // Align symbol timing.
    // Estimate carrier frequency (to about +-10kppm).
    // Estimate carrier phase (to about +-PI/4).
    // Adjust *ss accordingly.
    // Initialize AGC.
    // Return confidence (unbounded, 0=bad, 1=nominal).

    float find_plheader(sampler_state *pss, int search_range)
    {
        std::complex<T> best_corr = 0;
        int best_imu = 0;  // Avoid compiler warning.
        int best_pos = 0;  // Avoid compiler warning.

        // Symbol clock is not recovered yet, so we try fractional symbols.
        const int interp = 8;

        for (int imu=0; imu<interp; ++imu)
        {
            const int ndiffs = search_range + sof.LENGTH + plscodes.LENGTH;

            if (diffs) {
                delete[] diffs;
            }

            diffs = new std::complex<T>[ndiffs];
            sampler_state ss = *pss;
            ss.mu += imu * ss.omega / interp;

            // Compute rotation between consecutive symbols.
            std::complex<T> prev = 0;
            for (int i=0; i<ndiffs; ++i)
            {
                std::complex<T> p = interp_next(&ss);
                diffs[i] = conjprod(prev, p);
                prev = p;
            }

            // Find best PLHEADER candidate position.
            const int ncorrs = search_range;
            for (int i=0; i<ncorrs; ++i)
            {
                std::complex<T> c = correlate_plheader_diff(&diffs[i]);
                //if ( cnorm2(c) > cnorm2(best_corr) ) {
                // c.imag()>0 enforces frequency error +-Fm/4
                if (cnorm2(c)>cnorm2(best_corr) && c.imag()>0)
                {
                    best_corr = c;
                    best_imu = imu;
                    best_pos = i;
                }
            }
        }  // imu

        // Setup sampler according to best match.
        pss->mu += best_imu * pss->omega / interp;
        pss->skip_symbols(best_pos);
        pss->normalize();
#if 0
        // Lowpass-filter the differential correlator.
        // (Does not help much.)
        static std::complex<float> acc = 0;
        static const float k = 0.05;
        acc = best_corr*k + acc*(1-k);
        best_corr = acc;
#endif
        // Get rough estimate of carrier frequency from differential correlator.
        // (best_corr is nominally +j).
        float freqw = atan2f(-best_corr.real(), best_corr.imag());
        pss->fw16 += freqw * 65536 / (2*M_PI);
        // Force refresh because correction may be large.
        sampler->update_freq(pss->fw16/omega0);

        // Interpolate SOF with initial frequency estimation.
        // Estimate phase by correlation.
        // Initialize AGC (naive).
        float q;

        {
            sampler_state ss = *pss;
            float power = 0;
            std::complex<T> symbs[sof.LENGTH];

            for (int i=0; i<sof.LENGTH; ++i)
            {
                symbs[i] = interp_next(&ss);
                power += cnorm2(symbs[i]);
            }

            std::complex<float> c = conjprod(sof.symbols, symbs, sof.LENGTH);
            c *= 1.0f / sof.LENGTH;
            align_phase(pss, c);
            float signal_amp = sqrtf(power/sof.LENGTH);
            q = sqrtf(cnorm2(c)) / (cstln_amp*signal_amp);
            pss->gain = cstln_amp / signal_amp;
        }

        return q;
    }

    // Correlate PLHEADER.

    std::complex<float> correlate_plheader_diff(std::complex<T> *diffs)
    {
        std::complex<T> csof = correlate_sof_diff(diffs);
        std::complex<T> cplsc = correlate_plscode_diff(&diffs[sof.LENGTH]);
        // Use csof+cplsc or csof-cplsc, whichever maximizes likelihood.
        std::complex<T> c0 = csof + cplsc;  // Best when b7==0 (pilots off)
        std::complex<T> c1 = csof - cplsc;  // Best when b7==1 (pilots on)
        std::complex<T> c = (cnorm2(c0)>cnorm2(c1)) ? c0 : c1;
        return c * (1.0f/(26-1+64/2));
    }

    // Correlate 25 differential transitions in SOF.

    std::complex<float> correlate_sof_diff(std::complex<T> *diffs)
    {
        std::complex<T> c = 0;
        const uint32_t dsof = sof.VALUE ^ (sof.VALUE>>1);

        for (int i=0; i<sof.LENGTH; ++i)
        {
            // Constant  odd bit => +PI/4
            // Constant even bit => -PI/4
            // Toggled   odd bit => -PI/4
            // Toggled  even bit => +PI/4
            if (((dsof>>(sof.LENGTH-1-i)) ^ i) & 1) {
                c += diffs[i];
            } else {
                c -= diffs[i];
            }
        }

        return c;
    }

    // Correlate 32 data-independent transitions in PLSCODE.

    std::complex<float> correlate_plscode_diff(std::complex<T> *diffs)
    {
        std::complex<T> c = 0;
        uint64_t dscr = plscodes.SCRAMBLING ^ (plscodes.SCRAMBLING>>1);

        for (int i=1; i<plscodes.LENGTH; i+=2)
        {
            if ( (dscr>>(plscodes.LENGTH-1-i)) & 1 ) {
                c -= diffs[i];
            } else {
                c += diffs[i];
            }
        }

        return c;
    }

    // Adjust carrier frequency in *pss to match target phase after ns symbols.

    void adjust_freq(sampler_state *pss, int ns, const sampler_state *pnext)
    {
        // Note: Minimum deviation from current estimate.
        float adj = fmodfs(pnext->ph16-(pss->ph16+pss->fw16*ns),65536.0f) / ns;
        // 2sps vcm avec adj 10711K
        // 2sps vcm avec adj/2 10265k
        // 2sps vcm sans adj 8060K
        // 5sps 2MS1 avec adj 2262K
        // 5sps 2MS1 avec adj/2 3109K
        // 5sps 2MS1 avec adj/3 3254K
        // 5sps 2MS1 sans adj 3254K
        // 1.2sps oldbeacon avec adj 5774K
        // 1.2sps oldbeacon avec adj/2 15M
        // 1.2sps oldbeacon avec adj/3 15.6M max 17M
        // 1.2sps oldbeacon sans adj 14M malgré drift
        pss->fw16 += adj;
    }

    // Estimate frequency from known symbols by differential correlation.
    // Adjust *ss accordingly.
    // Retroactively frequency-shift the samples in-place.
    //
    // *ss must point after the sampled symbols.
    // expect[] must be PSK with amplitude cstln_amp.
    // Idempotent.
    // Not affected by phase error nor by gain mismatch.
    // Can handle +-25% error.
    // Result is typically such that residual phase error over a PLHEADER
    // spans less than 90°.

    void match_freq(
        std::complex<float> *expect,
        std::complex<float> *recv,
        int ns,
		sampler_state *ss)
    {
        if (sch->debug) {
            fprintf(stderr, "match_freq\n");
        }

        std::complex<float> diff = 0;

        for (int i=0; i<ns-1; ++i)
        {
            std::complex<float> de = conjprod(expect[i], expect[i+1]);
            std::complex<float> dr = conjprod(recv[i], recv[i+1]);
            diff += conjprod(de, dr);
        }

        float dfw16 = atan2f(diff.imag(),diff.real()) * 65536 / (2*M_PI);

        // Derotate.
        for (int i=0; i<ns; ++i) {
            recv[i] *= trig.expi(-dfw16*i);
        }

        ss->fw16 += dfw16;
        ss->ph16 += dfw16 * ns;  // Retroactively
    }

    // Interpolate a pilot block.
    // Perform ML match.

    float interp_match_pilot(sampler_state *pss)
    {
        std::complex<T> symbols[pilot.LENGTH];
        std::complex<T> expected[pilot.LENGTH];

        for (int i=0; i<pilot.LENGTH; ++i)
        {
            std::complex<float> p = interp_next(pss) * pss->gain;
            symbols[i] = descramble(pss, p);
            expected[i] = pilot.symbol;
            //fprintf(stderr, "%f %f\n", symbols[i].real(), symbols[i].imag());
        }

        return match_ph_amp(expected, symbols, pilot.LENGTH, pss);
    }

    // Interpolate a SOF.
    // Perform ML match.

    float interp_match_sof(sampler_state *pss)
    {
        std::complex<T> symbols[pilot.LENGTH];

        for (int i=0; i<sof.LENGTH; ++i) {
            symbols[i] = interp_next(pss) * pss->gain;
        }

        return match_ph_amp(sof.symbols, symbols, sof.LENGTH, pss);
    }

    // Estimate phase and amplitude from known symbols.
    // Adjust *ss accordingly.
    // Retroactively derotate and scale the samples in-place.
    // Return MER^2.
    //
    // *ss must point after the sampled symbols, with gain applied.
    // expect[] must be PSK (not APSK) with amplitude cstln_amp.
    // Idempotent.

    float match_ph_amp(
        std::complex<float> *expect,
        std::complex<float> *recv,
        int ns,
		sampler_state *ss
    )
    {
        std::complex<float> rr = 0;

        for (int i=0; i<ns; ++i) {
            rr += conjprod(expect[i], recv[i]);
        }

        rr *= 1.0f / (ns*cstln_amp);
        float dph16 = atan2f(rr.imag(),rr.real()) * 65536 / (2*M_PI);
        ss->ph16 += dph16;
        rr *= trig.expi(-dph16);
        // rr.real() is now the modulation amplitude.
        float dgain = cstln_amp / rr.real();
        ss->gain *= dgain;
        // Rotate and scale.  Compute error power.
        std::complex<float> adj = trig.expi(-dph16) * dgain;
        float ev2 = 0;

        for (int i=0; i<ns; ++i)
        {
            recv[i] *= adj;
            ev2 += cnorm2(recv[i]-expect[i]);
        }

        // Return MER^2.
        ev2 *= 1.0f / (ns*cstln_amp*cstln_amp);
        return 1.0f / ev2;
    }

    // Adjust frequency in *pss by an integer number of cycles per data block
    // so that phases align best on data symbols.
    //
    // *pss must point to the beginning of a frame.

    void match_frame(
        sampler_state *pss,
        const s2_pls *pls,
        int S,
		cstln_lut<SOFTSYMB,256> *dcstln
    )
    {
        if (sch->debug) {
            fprintf(stderr, "match_frame\n");
        }

        bool pilots = pls->pilots; // force to true for lighter processing
        // With pilots: Use first block of data slots.
        // Without pilots: Use whole frame.
        int ns = pilots ? 16*90 : S*90;
        // Pilots: steps of ~700 ppm (= 1 cycle between pilots)
        // No pilots, normal frames: steps of ~30(QPSK) - ~80(32APSK) ppm
        // No pilots, short frames: steps of ~120(QPSK) - 300(32APSK) ppm
        int nwrap = pilots ? 16*90+pilot.LENGTH : S*90+sof.LENGTH;
        // Frequency search range.
        int sliprange = pilots ? 10 : 50;  // TBD Customizable ?
        float besterr = 1e99;
        float bestslip = 0;  // Avoid compiler warning
        int err_div = ns * cstln_amp * cstln_amp;

        for (int slip = -sliprange; slip <= sliprange; ++slip)
        {
            sampler_state ssl = *pss;
            float dfw = slip * 65536.0f / nwrap;
            ssl.fw16 += dfw;
            // Apply retroactively from midpoint of preceeding PLHEADER,
            // where the phase from match_ph_amp is most reliable.
            ssl.ph16 += dfw * (plscodes.LENGTH + sof.LENGTH) / 2;
            float err = 0;

            for (int s = 0; s < ns; ++s)
            {
                std::complex<float> p = interp_next(&ssl) * ssl.gain;
                typename cstln_lut<SOFTSYMB,256>::result *cr =
                    dcstln->lookup(p.real(), p.imag());
                float evreal = p.real() - dcstln->symbols[cr->symbol].real();
                float evimag = p.imag() - dcstln->symbols[cr->symbol].imag();
                err += evreal*evreal + evimag*evimag;
            }

            err /= err_div;

            if (err < besterr)
            {
                besterr = err;
                bestslip = slip;
            }
#if DEBUG_CARRIER
        fprintf(stderr, "slip %+3d  %6.0f ppm  err=%f\n",
            slip, ssl.fw16*1e6/65536, err);
#endif
        }

        pss->fw16 += bestslip * 65536.0f / nwrap;
    }  // match_frame

    void shutdown()
    {
        if (sch->verbose)
        {
            fprintf(
                stderr,
                "PL errors: %d/%d (%.0f ppm)\n",
                pls_total_errors,
                pls_total_count,
                1e6 * pls_total_errors / pls_total_count
            );
        }
    }

    std::complex<float> descramble(sampler_state *ss, const std::complex<float> &p)
    {
        int r = *ss->scr++;
        std::complex<float> res;

        switch (r)
        {
        case 3:
            res.real(-p.imag());
            res.imag(p.real());
            break;
        case 2:
            res.real(-p.real());
            res.imag(-p.imag());
            break;
        case 1:
            res.real(p.imag());
            res.imag(-p.real());
            break;
        default:
            res = p;
        }

        return res;
    }

    // Interpolator

    inline std::complex<float> interp_next(sampler_state *ss)
    {
        // Skip to next sample
        while (ss->mu >= 1)
        {
            ++ss->p;
            ss->mu-=1.0f;
        }
        // Interpolate
#if 0
        // Interpolate linearly then derotate.
        // This will fail with large carrier offsets (e.g. --tune).
        float cmu = 1.0f - ss->mu;
        std::complex<float> s(ss->p[0].real()*cmu + ss->p[1].real()*ss->mu,
                ss->p[0].imag()*cmu + ss->p[1].imag()*ss->mu);
        ss->mu += ss->omega;
        // Derotate
        const std::complex<float> &rot = trig.expi(-ss->ph16);
        ss->ph16 += ss->fw16;
        return rot * s;
#else
        // Use generic interpolator
        std::complex<float> s = sampler->interp(ss->p, ss->mu, ss->ph16);
        ss->mu += ss->omega;
        ss->ph16 += ss->fw16;
        return s;
#endif
    }

    // Adjust phase in [ss] to cancel offset observed as [c].

    void align_phase(sampler_state *ss, const std::complex<float> &c)
    {
        float err = atan2f(c.imag(),c.real()) * 65536 / (2*M_PI);
        ss->ph16 += err;
    }

    inline uint8_t track_symbol(
        sampler_state *ss,
        const std::complex<float> &p,
		cstln_lut<SOFTSYMB,256> *c
    )
    {
        static const float kph = 4e-2;
        static const float kfw = 1e-4;
        // Decision
        typename cstln_lut<SOFTSYMB,256>::result *cr = c->lookup(p.real(), p.imag());
        // Carrier tracking
        ss->ph16 += cr->phase_error * kph;
        ss->fw16 += cr->phase_error * kfw;

        if (ss->fw16 < min_freqw16) {
            ss->fw16 = min_freqw16;
        }

        if (ss->fw16 > max_freqw16) {
            ss->fw16 = max_freqw16;
        }

        return cr->symbol;
    }

  public:
    cstln_lut<SOFTSYMB,256> *qpsk;
    s2_plscodes<T> plscodes;
    cstln_lut<SOFTSYMB,256> *cstlns[32];  // Constellations in use, by modcod

    cstln_lut<SOFTSYMB,256> *get_cstln(int modcod)
    {
        if (!cstlns[modcod])
        {
            const modcod_info *mcinfo = &modcod_infos[modcod];

            if (sch->debug)
            {
                fprintf(
                    stderr,
                    "Creating LUT for %s ratecode %d\n",
                    cstln_base::names[mcinfo->c],
                    mcinfo->rate
                );
            }

            cstlns[modcod] = new cstln_lut<SOFTSYMB,256>(
                mcinfo->c,
                mcinfo->esn0_nf,
                mcinfo->g1,
                mcinfo->g2,
                mcinfo->g3
            );
#if 0
            fprintf(stderr, "Dumping constellation LUT to stdout.\n");
            cstlns[modcod]->dump(stdout);
            exit(0);
#endif
        }

        return cstlns[modcod];
    }

    cstln_lut<SOFTSYMB,256> *cstln;  // Last seen, or NULL (legacy)
    trig16 trig;
    pipereader< std::complex<T> > in;
    pipewriter< plslot<SOFTSYMB> > out;
    int meas_count;
    pipewriter<float> *freq_out, *ss_out, *mer_out;
    pipewriter< std::complex<float> > *cstln_out;
    pipewriter< std::complex<float> > *cstln_pls_out;
    pipewriter< std::complex<float> > *symbols_out;
    pipewriter<int> *state_out;
    bool first_run;
    // S2 constants
    s2_scrambling scrambling;
    s2_sof<T> sof;
    s2_pilot<T> pilot;
    // Performance stats on PL signalling
    uint32_t pls_total_errors, pls_total_count;
    int m_modcodType;
    int m_modcodRate;
    bool m_locked;

private:
    std::complex<T> *diffs;
    sampler_state *sspilots;
  };  // s2_frame_receiver

template <typename SOFTBYTE>
struct fecframe
{
    s2_pls pls;
    SOFTBYTE bytes[64800 / 8]; // Contains 16200/8 or 64800/8 bytes.
};

// S2 INTERLEAVER
// EN 302 307-1 section 5.3.3 Bit Interleaver

struct s2_interleaver : runnable
{
    s2_interleaver(
        scheduler *sch,
        pipebuf<fecframe<hard_sb>> &_in,
        pipebuf<plslot<hard_ss>> &_out
    ) :
        runnable(sch, "S2 interleaver"),
        in(_in),
        out(_out, 1 + 360)
    {
    }

    void run()
    {
        while (in.readable() >= 1)
        {
            const s2_pls *pls = &in.rd()->pls;
            const modcod_info *mcinfo = check_modcod(pls->modcod);
            int nslots = pls->sf ? mcinfo->nslots_nf / 4 : mcinfo->nslots_nf;

            if (out.writable() < 1 + nslots) {
                return;
            }

            const hard_sb *pbytes = in.rd()->bytes;
            // Output pseudo slot with PLS.
            plslot<hard_ss> *ppls = out.wr();
            ppls->is_pls = true;
            ppls->pls = *pls;
            out.written(1);
            // Interleave
            plslot<hard_ss> *pout = out.wr();

            if (mcinfo->nsymbols == 4)
            {
                serialize_qpsk(pbytes, nslots, pout);
            }
            else
            {
                int bps = log2(mcinfo->nsymbols);
                int rows = pls->framebits() / bps;

                if (mcinfo->nsymbols == 8 && mcinfo->rate == FEC35) {
                    interleave(bps, rows, pbytes, nslots, false, pout);
                } else {
                    interleave(bps, rows, pbytes, nslots, true, pout);
                }
            }

            in.read(1);
            out.written(nslots);
        }
    }

  private:
    // Fill slots with serialized QPSK symbols, MSB first.
    static void serialize_qpsk(const hard_sb *pin, int nslots,
                               plslot<hard_ss> *pout)
    {
#if 0 // For reference
      hard_sb acc;
      int nacc = 0;
      for ( ; nslots; --nslots,++pout ) {
	pout->is_pls = false;
	hard_ss *ps = pout->symbols;
	for ( int ns=pout->LENGTH; ns--; ++ps ) {
	  if ( nacc < 2 ) { acc=*pin++; nacc=8; }
	  *ps = acc>>6;
	  acc <<= 2;
	  nacc -= 2;
	}
      }
      if ( nacc ) fail("Bug: s2_interleaver");
#else
        if (nslots % 2) {
            fatal("Bug: Truncated byte");
        }

        for (; nslots; nslots -= 2)
        {
            hard_sb b;
            hard_ss *ps;
            // Slot 0 (mod 2)
            pout->is_pls = false;
            ps = pout->symbols;

            for (int i = 0; i < 22; ++i)
            {
                b = *pin++;
                *ps++ = (b >> 6);
                *ps++ = (b >> 4) & 3;
                *ps++ = (b >> 2) & 3;
                *ps++ = (b)&3;
            }

            b = *pin++;
            *ps++ = (b >> 6);
            *ps++ = (b >> 4) & 3;
            // Slot 1 (mod 2)
            ++pout;
            pout->is_pls = false;
            ps = pout->symbols;
            *ps++ = (b >> 2) & 3;
            *ps++ = (b)&3;

            for (int i = 0; i < 22; ++i)
            {
                b = *pin++;
                *ps++ = (b >> 6);
                *ps++ = (b >> 4) & 3;
                *ps++ = (b >> 2) & 3;
                *ps++ = (b)&3;
            }

            ++pout;
        }
#endif
    }

    // Fill slots with interleaved symbols.
    // EN 302 307-1 figures 7 and 8
#if 0  // For reference
    static void interleave(int bps, int rows,
			   const hard_sb *pin, int nslots,
			   bool msb_first, plslot<hard_ss> *pout) {
      if ( bps==4 && rows==4050 && msb_first )
	return interleave4050(pin, nslots, pout);
      if ( rows % 8 ) fatal("modcod/framesize combination not supported\n");
      int stride = rows/8;  // Offset to next column, in bytes
      hard_sb accs[bps];    // One accumulator per column
      int nacc = 0;         // Bits in each column accumulator
      for ( ; nslots; --nslots,++pout ) {
	pout->is_pls = false;
	hard_ss *ps = pout->symbols;
	for ( int ns=pout->LENGTH; ns--; ++ps ) {
	  if ( ! nacc ) {
	    const hard_sb *pi = pin;
	    for ( int b=0; b<bps; ++b,pi+=stride ) accs[b] = *pi;
	    ++pin;
	    nacc = 8;
	  }
	  hard_ss symb = 0;
	  if ( msb_first )
	    for ( int b=0; b<bps; ++b ) {
	      symb = (symb<<1) | (accs[b]>>7);
	      accs[b] <<= 1;
	    }
	  else
	    for ( int b=bps; b--; ) {
	      symb = (symb<<1) | (accs[b]>>7);
	      accs[b] <<= 1;
	    }
	  --nacc;
	  *ps = symb;
	}
      }
      if ( nacc ) fail("Bug: s2_interleaver");
    }
#else  // reference
    static void interleave(int bps, int rows,
                           const hard_sb *pin, int nslots,
                           bool msb_first, plslot<hard_ss> *pout)
    {
        void (*func)(int rows, const hard_sb *pin, int nslots,
                     plslot<hard_ss> *pout) = 0;

        if (msb_first)
        {
            switch (bps)
            {
            case 2:
                func = interleave<1, 2>;
                break;
            case 3:
                func = interleave<1, 3>;
                break;
            case 4:
                func = interleave<1, 4>;
                break;
            case 5:
                func = interleave<1, 5>;
                break;
            default:
                fail("Bad bps");
            }
        }
        else
        {
            switch (bps)
            {
            case 2:
                func = interleave<0, 2>;
                break;
            case 3:
                func = interleave<0, 3>;
                break;
            case 4:
                func = interleave<0, 4>;
                break;
            case 5:
                func = interleave<0, 5>;
                break;
            default:
                fail("Bad bps");
            }
        }

        (*func)(rows, pin, nslots, pout);
    }

    template <int MSB_FIRST, int BPS>
    static void interleave(int rows, const hard_sb *pin, int nslots,
                           plslot<hard_ss> *pout)
    {
        if (BPS == 4 && rows == 4050 && MSB_FIRST) {
            return interleave4050(pin, nslots, pout);
        }

        if (rows % 8) {
            fatal("modcod/framesize combination not supported\n");
        }

        int stride = rows / 8; // Offset to next column, in bytes

        if (nslots % 4) {
            fatal("Bug: Truncated byte");
        }

        // plslot::symbols[] are not packed across slots,
        // so we need tos split bytes at boundaries.
        for (; nslots; nslots -= 4)
        {
            hard_sb accs[BPS]; // One accumulator per column
            hard_ss *ps;
            // Slot 0 (mod 4): 88+2
            pout->is_pls = false;
            ps = pout->symbols;

            for (int i = 0; i < 11; ++i)
            {
                split_byte<BPS>(pin++, stride, accs);
                pop_symbols<MSB_FIRST, BPS>(accs, &ps, 8);
            }

            split_byte<BPS>(pin++, stride, accs);
            pop_symbols<MSB_FIRST, BPS>(accs, &ps, 2);
            ++pout;
            // Slot 1 (mod 4): 6+80+4
            pout->is_pls = false;
            ps = pout->symbols;
            pop_symbols<MSB_FIRST, BPS>(accs, &ps, 6);

            for (int i = 0; i < 10; ++i)
            {
                split_byte<BPS>(pin++, stride, accs);
                pop_symbols<MSB_FIRST, BPS>(accs, &ps, 8);
            }

            split_byte<BPS>(pin++, stride, accs);
            pop_symbols<MSB_FIRST, BPS>(accs, &ps, 4);
            ++pout;
            // Slot 2 (mod 4): 4+80+6
            pout->is_pls = false;
            ps = pout->symbols;
            pop_symbols<MSB_FIRST, BPS>(accs, &ps, 4);

            for (int i = 0; i < 10; ++i)
            {
                split_byte<BPS>(pin++, stride, accs);
                pop_symbols<MSB_FIRST, BPS>(accs, &ps, 8);
            }

            split_byte<BPS>(pin++, stride, accs);
            pop_symbols<MSB_FIRST, BPS>(accs, &ps, 6);
            ++pout;
            // Slot 3 (mod 4): 2+88
            pout->is_pls = false;
            ps = pout->symbols;
            pop_symbols<MSB_FIRST, BPS>(accs, &ps, 2);

            for (int i = 0; i < 11; ++i)
            {
                split_byte<BPS>(pin++, stride, accs);
                pop_symbols<MSB_FIRST, BPS>(accs, &ps, 8);
            }

            ++pout;
        }
    }

    template <int BPS>
    static inline void split_byte(const hard_sb *pi, int stride,
                                  hard_sb accs[BPS])
    {
        // TBD Pass stride as template parameter.
        for (int b = 0; b < BPS; ++b, pi += stride) {
            accs[b] = *pi;
        }
    }

    template <int MSB_FIRST, int BPS>
    static void pop_symbols(hard_sb accs[BPS], hard_ss **ps, int ns)
    {
        for (int i = 0; i < ns; ++i)
        {
            hard_ss symb = 0;
            // Check unrolling and constant propagation.
            for (int b = 0; b < BPS; ++b)
            {
                if (MSB_FIRST) {
                    symb = (symb << 1) | (accs[b] >> 7);
                } else {
                    symb = (symb << 1) | (accs[BPS - 1 - b] >> 7);
                }
            }

            for (int b = 0; b < BPS; ++b) {
                accs[b] <<= 1;
            }

            *(*ps)++ = symb;
        }
    }
#endif // reference

    // Special case for 16APSK short frames.
    // 4050 rows is not a multiple of 8.
    static void interleave4050(const hard_sb *pin, int nslots,
                               plslot<hard_ss> *pout)
    {
        hard_sb accs[4]; // One accumulator per column
        int nacc = 0;    // Bits in each column accumulator

        for (; nslots; --nslots, ++pout)
        {
            pout->is_pls = false;
            hard_ss *ps = pout->symbols;

            for (int ns = pout->LENGTH; ns--; ++ps)
            {
                if (!nacc)
                {
                    if (nslots == 1 && ns == 1)
                    {
                        // Special case just to avoid reading beyond end of buffer
                        accs[0] = pin[0];
                        accs[1] = (pin[506] << 2) | (pin[507] >> 6);
                        accs[2] = (pin[1012] << 4) | (pin[1013] >> 4);
                        accs[3] = (pin[1518] << 6);
                    }
                    else
                    {
                        accs[0] = pin[0];
                        accs[1] = (pin[506] << 2) | (pin[507] >> 6);
                        accs[2] = (pin[1012] << 4) | (pin[1013] >> 4);
                        accs[3] = (pin[1518] << 6) | (pin[1519] >> 2);
                    }

                    ++pin;
                    nacc = 8;
                }

                hard_ss symb = 0;

                for (int b = 0; b < 4; ++b)
                {
                    symb = (symb << 1) | (accs[b] >> 7);
                    accs[b] <<= 1;
                }

                --nacc;
                *ps = symb;
            }
        }
    }

    pipereader<fecframe<hard_sb>> in;
    pipewriter<plslot<hard_ss>> out;
}; // s2_interleaver

// S2 DEINTERLEAVER
// EN 302 307-1 section 5.3.3 Bit Interleaver

template <typename SOFTSYMB, typename SOFTBYTE>
struct s2_deinterleaver : runnable
{
    s2_deinterleaver(
        scheduler *sch,
        pipebuf<plslot<SOFTSYMB>> &_in,
        pipebuf<fecframe<SOFTBYTE>> &_out
    ) :
        runnable(sch, "S2 deinterleaver"),
        in(_in),
        out(_out)
    {
    }

    void run()
    {
        while (in.readable() >= 1 && out.writable() >= 1)
        {
            plslot<SOFTSYMB> *pin = in.rd();

            if (!pin->is_pls) {
                fail("s2_deinterleaver: bad input sequence");
            }

            s2_pls *pls = &pin->pls;
            const modcod_info *mcinfo = check_modcod(pls->modcod);
            int nslots = pls->sf ? mcinfo->nslots_nf / 4 : mcinfo->nslots_nf;

            if (in.readable() < 1 + nslots) {
                return;
            }

            fecframe<SOFTBYTE> *pout = out.wr();
            pout->pls = *pls;
            SOFTBYTE *pbytes = pout->bytes;

            if (mcinfo->nsymbols == 4)
            {
                deserialize_qpsk(pin + 1, nslots, pbytes);
            }
            else
            {
                int bps = log2(mcinfo->nsymbols);
                int rows = pls->framebits() / bps;

                if ((mcinfo->nsymbols == 8) && (mcinfo->rate == FEC35)) {
                    deinterleave(bps, rows, pin + 1, nslots, false, pbytes);
                } else {
                    deinterleave(bps, rows, pin + 1, nslots, true, pbytes);
                }
            }

            in.read(1 + nslots);
            out.written(1);
        }
    }

  private:
    // Deserialize slots of QPSK symbols, MSB first.
    static void deserialize_qpsk(plslot<SOFTSYMB> *pin, int nslots,
                                 SOFTBYTE *pout)
    {
        SOFTBYTE acc;
        softword_clear(&acc); // gcc warning
        int nacc = 0;

        for (; nslots; --nslots, ++pin)
        {
            SOFTSYMB *ps = pin->symbols;

            for (int ns = pin->LENGTH; ns--; ++ps)
            {
                pack_qpsk_symbol(*ps, &acc, nacc);
                nacc += 2;

                if (nacc == 8)
                { // TBD unroll
                    *pout++ = acc;
                    nacc = 0;
                }
            }
        }
    }

    // Deinterleave slots of symbols.
    // EN 302 307-1 figures 7 and 8
#if 0  // For reference
    static void deinterleave(int bps, int rows,
			     const plslot<SOFTSYMB> *pin, int nslots,
			     bool msb_first, SOFTBYTE *pout) {
      if ( bps==4 && rows==4050 && msb_first )
	return deinterleave4050(pin, nslots, pout);
      if ( rows % 8 ) fatal("modcod/framesize combination not supported\n");
      int stride = rows/8;  // Offset to next column, in bytes
      SOFTBYTE accs[bps];
      for ( int b=0; b<bps; ++b ) softword_clear(&accs[b]);  // gcc warning
      int nacc = 0;
      for ( ; nslots; --nslots,++pin ) {
	const SOFTSYMB *ps = pin->symbols;
	for ( int ns=pin->LENGTH; ns--; ++ps ) {
	  split_symbol(*ps, bps, accs, nacc, msb_first);
	  ++nacc;
	  if ( nacc == 8 ) {
	    SOFTBYTE *po = pout;
	    for ( int b=0; b<bps; ++b,po+=stride ) *po = accs[b];
	    ++pout;
	    nacc = 0;
	  }
	}
      }
      if ( nacc ) fail("Bug: s2_deinterleaver");
    }
#else  // reference
    static void deinterleave(int bps, int rows,
                             const plslot<SOFTSYMB> *pin, int nslots,
                             bool msb_first, SOFTBYTE *pout)
    {
        void (*func)(int rows, const plslot<SOFTSYMB> *pin, int nslots,
                     SOFTBYTE *pout) = 0;

        if (msb_first)
        {
            switch (bps)
            {
            case 2:
                func = deinterleave<1, 2>;
                break;
            case 3:
                func = deinterleave<1, 3>;
                break;
            case 4:
                func = deinterleave<1, 4>;
                break;
            case 5:
                func = deinterleave<1, 5>;
                break;
            default:
                fail("Bad bps");
            }
        }
        else
        {
            switch (bps)
            {
            case 2:
                func = deinterleave<0, 2>;
                break;
            case 3:
                func = deinterleave<0, 3>;
                break;
            case 4:
                func = deinterleave<0, 4>;
                break;
            case 5:
                func = deinterleave<0, 5>;
                break;
            default:
                fail("Bad bps");
            }
        }

        (*func)(rows, pin, nslots, pout);
    }

    template <int MSB_FIRST, int BPS>
    static void deinterleave(int rows, const plslot<SOFTSYMB> *pin, int nslots,
                             SOFTBYTE *pout)
    {
        if (BPS == 4 && rows == 4050 && MSB_FIRST) {
            return deinterleave4050(pin, nslots, pout);
        }

        if (rows % 8) {
            fatal("modcod/framesize combination not supported\n");
        }

        int stride = rows / 8; // Offset to next column, in bytes
        SOFTBYTE accs[BPS];

        for (int b = 0; b < BPS; ++b) {
            softword_clear(&accs[b]); // gcc warning
        }

        int nacc = 0;

        for (; nslots; --nslots, ++pin)
        {
            const SOFTSYMB *ps = pin->symbols;

            for (int ns = pin->LENGTH; ns--; ++ps)
            {
                split_symbol(*ps, BPS, accs, nacc, MSB_FIRST);
                ++nacc;

                if (nacc == 8)
                { // TBD Unroll, same as interleave()
                    SOFTBYTE *po = pout;

                    // TBD Pass stride as template parameter.
                    for (int b = 0; b < BPS; ++b, po += stride) {
                        *po = accs[b];
                    }

                    ++pout;
                    nacc = 0;
                }
            }
        }

        if (nacc) {
            fail("Bug: s2_deinterleaver");
        }
    }
#endif // reference

    // Special case for 16APSK short frames.
    // 4050 rows is not a multiple of 8
    // so we process rows one at a time rather than in chunks of 8.
    static void deinterleave4050(const plslot<SOFTSYMB> *pin, int nslots,
                                 SOFTBYTE *pout)
    {
        const int rows = 4050;
        SOFTBYTE accs[4];

        for (int b = 0; b < 4; ++b) {
            softword_clear(&accs[b]); // gcc warning
        }

        int nacc = 0;

        for (; nslots; --nslots, ++pin)
        {
            const SOFTSYMB *ps = pin->symbols;

            for (int ns = pin->LENGTH; ns--; ++ps)
            {
                split_symbol(*ps, 4, accs, nacc, true);
                ++nacc;

                if (nacc == 8)
                {
                    for (int b = 0; b < 8; ++b)
                    {
                        softwords_set(pout, rows * 0 + b, softword_get(accs[0], b));
                        softwords_set(pout, rows * 1 + b, softword_get(accs[1], b));
                        softwords_set(pout, rows * 2 + b, softword_get(accs[2], b));
                        softwords_set(pout, rows * 3 + b, softword_get(accs[3], b));
                    }

                    ++pout;
                    nacc = 0;
                }
            }
        }

        if (nacc != 2) {
            fatal("Bug: Expected 2 leftover rows\n");
        }

        // Pad with random symbol so that we can use accs[].
        for (int b = nacc; b < 8; ++b) {
            split_symbol(pin->symbols[0], 4, accs, b, true);
        }

        for (int b = 0; b < nacc; ++b)
        {
            softwords_set(pout, rows * 0 + b, softword_get(accs[0], b));
            softwords_set(pout, rows * 1 + b, softword_get(accs[1], b));
            softwords_set(pout, rows * 2 + b, softword_get(accs[2], b));
            softwords_set(pout, rows * 3 + b, softword_get(accs[3], b));
        }
    }

    // Spread LLR symbol across hard columns.
    // Must call 8 times before using result because we use bit shifts.
    static inline void split_symbol(const llr_ss &ps, int bps,
                                    hard_sb accs[/*bps*/], int nacc,
                                    bool msb_first)
    {
        (void) nacc;

        if (msb_first)
        {
            for (int b = 0; b < bps; ++b) {
                accs[b] = (accs[b] << 1) | llr_harden(ps.bits[bps - 1 - b]);
            }
        }
        else
        {
            for (int b = 0; b < bps; ++b) {
                accs[b] = (accs[b] << 1) | llr_harden(ps.bits[b]);
            }
        }
    }

    // Fast variant
    template <int MSB_FIRST, int BPS>
    static inline void split_symbol(const llr_ss &ps,
                                    hard_sb accs[/*bps*/], int nacc)
    {
        (void)nacc;
        
        if (MSB_FIRST)
        {
            for (int b = 0; b < BPS; ++b) {
                accs[b] = (accs[b] << 1) | llr_harden(ps.bits[BPS - 1 - b]);
            }
        }
        else
        {
            for (int b = 0; b < BPS; ++b) {
                accs[b] = (accs[b] << 1) | llr_harden(ps.bits[b]);
            }
        }
    }

    // Spread LLR symbol across LLR columns.
    static inline void split_symbol(
        const llr_ss &ps,
        int bps,
        llr_sb accs[/*bps*/],
        int nacc,
        bool msb_first
    )
    {
        if (msb_first)
        {
            for (int b = 0; b < bps; ++b) {
                accs[b].bits[nacc] = ps.bits[bps - 1 - b];
            }
        }
        else
        {
            for (int b = 0; b < bps; ++b) {
                accs[b].bits[nacc] = ps.bits[b];
            }
        }
    }

    // Fast variant
    template <int MSB_FIRST, int BPS>
    static inline void split_symbol(
        const llr_ss &ps,
        llr_sb accs[/*bps*/],
        int nacc)
    {
        if (MSB_FIRST)
        {
            for (int b = 0; b < BPS; ++b) {
                accs[b].bits[nacc] = ps.bits[BPS - 1 - b];
            }
        }
        else
        {
            for (int b = 0; b < BPS; ++b) {
                accs[b].bits[nacc] = ps.bits[b];
            }
        }
    }

    // Merge QPSK LLR symbol into hard byte.
    static inline void pack_qpsk_symbol(
        const llr_ss &ps,
        hard_sb *acc,
        int nacc
    )
    {
        (void) nacc;
        // TBD Must match LLR law, see softsymb_harden.
        uint8_t s = llr_harden(ps.bits[0]) | (llr_harden(ps.bits[1]) << 1);
        *acc = (*acc << 2) | s;
    }

    // Merge QPSK LLR symbol into LLR byte.
    static inline void pack_qpsk_symbol(
        const llr_ss &ps,
        llr_sb *acc,
        int nacc
    )
    {
        acc->bits[nacc] = ps.bits[1];
        acc->bits[nacc + 1] = ps.bits[0];
    }

    pipereader<plslot<SOFTSYMB>> in;
    pipewriter<fecframe<SOFTBYTE>> out;
}; // s2_deinterleaver

typedef ldpc_table<uint16_t> s2_ldpc_table;
typedef ldpc_engine<bool, hard_sb, 8, uint16_t> s2_ldpc_engine;

#include "dvbs2_data.h"

static const struct fec_info
{
    static const int KBCH_MAX = 58192;
    int Kbch;  // BCH message size (bits)
    int kldpc; // LDPC message size (= BCH codeword size) (bits)
    int t;     // BCH error correction
    const s2_ldpc_table *ldpc;
}
fec_infos[2][FEC_COUNT] =
{
    {
        // Normal frames - must respect enum code_rate order
        {32208, 32400, 12, &ldpc_nf_fec12},  // FEC12 (was [FEC12] = {...} and so on. Does not compile with MSVC)
        {43040, 43200, 10, &ldpc_nf_fec23},  // FEC23
        {0, 0, 0, nullptr},                  // FEC46
        {48408, 48600, 12, &ldpc_nf_fec34},  // FEC34
        {53840, 54000, 10, &ldpc_nf_fec56},  // FEC56
        {0, 0, 0, nullptr},                  // FEC78
        {51648, 51840, 12, &ldpc_nf_fec45},  // FEC45
        {57472, 57600, 8, &ldpc_nf_fec89},   // FEC89
        {58192, 58320, 8, &ldpc_nf_fec910},  // FEC910
        {16008, 16200, 12, &ldpc_nf_fec14},  // FEC14
        {21408, 21600, 12, &ldpc_nf_fec13},  // FEC13
        {25728, 25920, 12, &ldpc_nf_fec25},  // FEC25
        {38688, 38880, 12, &ldpc_nf_fec35},  // FEC35
    },
    {
        // Short frames - must respect enum code_rate order
        {7032, 7200, 12, &ldpc_sf_fec12},    // FEC12 (was [FEC12] = {...} and so on. Does not compile with MSVC)
        {10632, 10800, 12, &ldpc_sf_fec23},  // FEC23
        {0, 0, 0, nullptr},                  // FEC46
        {11712, 11880, 12, &ldpc_sf_fec34},  // FEC34
        {13152, 13320, 12, &ldpc_sf_fec56},  // FEC56
        {0, 0, 0, nullptr},                  // FEC78
        {12432, 12600, 12, &ldpc_sf_fec45},  // FEC45
        {14232, 14400, 12, &ldpc_sf_fec89},  // FEC89
        {0, 0, 0, nullptr},                  // FEC910
        {3072, 3240, 12, &ldpc_sf_fec14},    // FEC14
        {5232, 5400, 12, &ldpc_sf_fec13},    // FEC13
        {6312, 6480, 12, &ldpc_sf_fec25},    // FEC25
        {9552, 9720, 12, &ldpc_sf_fec35},    // FEC35
    },
};

struct bbframe
{
    s2_pls pls;
    uint8_t bytes[58192 / 8]; // Kbch/8 max
};

// S2_LDPC_ENGINES
// Initializes LDPC engines for all DVB-S2 FEC settings.

template <typename SOFTBIT, typename SOFTBYTE>
struct s2_ldpc_engines
{
    typedef ldpc_engine<SOFTBIT, SOFTBYTE, 8, uint16_t> s2_ldpc_engine;
    s2_ldpc_engine *ldpcs[2][FEC_COUNT]; // [shortframes][fec]

    s2_ldpc_engines()
    {
        // memset(ldpcs, 0, sizeof(ldpcs)); // useless as initialization comes next

        for (int sf = 0; sf <= 1; ++sf)
        {
            for (int fec = 0; fec < FEC_COUNT; ++fec)
            {
                const fec_info *fi = &fec_infos[sf][fec];

                if (!fi->ldpc)
                {
                    ldpcs[sf][fec] = nullptr;
                }
                else
                {
                    int n = (sf ? 64800 / 4 : 64800);
                    int k = fi->kldpc;
                    ldpcs[sf][fec] = new s2_ldpc_engine(fi->ldpc, k, n);
                }
            }
        }
    }

    ~s2_ldpc_engines()
    {
        for (int sf = 0; sf <= 1; ++sf)
        {
            for (int fec = 0; fec < FEC_COUNT; ++fec)
            {
                if (ldpcs[sf][fec]) {
                    delete ldpcs[sf][fec];
                }
            }
        }
    }

    void print_node_stats()
    {
        for (int sf = 0; sf <= 1; ++sf)
        {
            for (int fec = 0; fec < FEC_COUNT; ++fec)
            {
                s2_ldpc_engine *ldpc = ldpcs[sf][fec];

                if (ldpc) {
                    ldpc->print_node_stats();
                }
            }
        }
    }
}; // s2_ldpc_engines

// S2_BCH_ENGINES
// Initializes BCH engines for all DVB-S2 FEC settings.

struct s2_bch_engines
{
    bch_interface *bchs[2][FEC_COUNT];
    // N=t*m
    // The generator of GF(2^m) is always g1.
    // Normal frames with 8, 10 or 12 polynomials.
    typedef bch_engine<uint32_t, 192, 17, 16, uint16_t, 0x002d> s2_bch_engine_nf12;
    typedef bch_engine<uint32_t, 160, 17, 16, uint16_t, 0x002d> s2_bch_engine_nf10;
    typedef bch_engine<uint32_t, 128, 17, 16, uint16_t, 0x002d> s2_bch_engine_nf8;
    // Short frames with 12 polynomials.
    typedef bch_engine<uint32_t, 168, 17, 14, uint16_t, 0x002b> s2_bch_engine_sf12;

    s2_bch_engines()
    {
        bitvect<uint32_t, 17> bch_polys[2][12]; // [shortframes][polyindex]

        // EN 302 307-1 5.3.1 Table 6a (polynomials for normal frames)
        bch_polys[0][0] = bitvect<uint32_t, 17>(0x1002d);  // g1
        bch_polys[0][1] = bitvect<uint32_t, 17>(0x10173);  // g2
        bch_polys[0][2] = bitvect<uint32_t, 17>(0x10fbd);  // g3
        bch_polys[0][3] = bitvect<uint32_t, 17>(0x15a55);  // g4
        bch_polys[0][4] = bitvect<uint32_t, 17>(0x11f2f);  // g5
        bch_polys[0][5] = bitvect<uint32_t, 17>(0x1f7b5);  // g6
        bch_polys[0][6] = bitvect<uint32_t, 17>(0x1af65);  // g7
        bch_polys[0][7] = bitvect<uint32_t, 17>(0x17367);  // g8
        bch_polys[0][8] = bitvect<uint32_t, 17>(0x10ea1);  // g9
        bch_polys[0][9] = bitvect<uint32_t, 17>(0x175a7);  // g10
        bch_polys[0][10] = bitvect<uint32_t, 17>(0x13a2d); // g11
        bch_polys[0][11] = bitvect<uint32_t, 17>(0x11ae3); // g12

        // EN 302 307-1 5.3.1 Table 6b (polynomials for short frames)
        bch_polys[1][0] = bitvect<uint32_t, 17>(0x402b);  // g1
        bch_polys[1][1] = bitvect<uint32_t, 17>(0x4941);  // g2
        bch_polys[1][2] = bitvect<uint32_t, 17>(0x4647);  // g3
        bch_polys[1][3] = bitvect<uint32_t, 17>(0x5591);  // g4
        bch_polys[1][4] = bitvect<uint32_t, 17>(0x6b55);  // g5
        bch_polys[1][5] = bitvect<uint32_t, 17>(0x6389);  // g6
        bch_polys[1][6] = bitvect<uint32_t, 17>(0x6ce5);  // g7
        bch_polys[1][7] = bitvect<uint32_t, 17>(0x4f21);  // g8
        bch_polys[1][8] = bitvect<uint32_t, 17>(0x460f);  // g9
        bch_polys[1][9] = bitvect<uint32_t, 17>(0x5a49);  // g10
        bch_polys[1][10] = bitvect<uint32_t, 17>(0x5811); // g11
        bch_polys[1][11] = bitvect<uint32_t, 17>(0x65ef); // g12

        // Redundant with fec_infos[], but needs static template argument.

        for (int sf = 0; sf <= 1; ++sf)
        {
            for (int fec = 0; fec < FEC_COUNT; ++fec) {
                bchs[sf][fec] = nullptr;
            }
        }

        bchs[0][FEC12] = new s2_bch_engine_nf12(bch_polys[0], 12);
        bchs[0][FEC23] = new s2_bch_engine_nf10(bch_polys[0], 10);
        bchs[0][FEC34] = new s2_bch_engine_nf12(bch_polys[0], 12);
        bchs[0][FEC56] = new s2_bch_engine_nf10(bch_polys[0], 10);
        bchs[0][FEC45] = new s2_bch_engine_nf12(bch_polys[0], 12);
        bchs[0][FEC89] = new s2_bch_engine_nf8(bch_polys[0], 8);
        bchs[0][FEC910] = new s2_bch_engine_nf8(bch_polys[0], 8);
        bchs[0][FEC14] = new s2_bch_engine_nf12(bch_polys[0], 12);
        bchs[0][FEC13] = new s2_bch_engine_nf12(bch_polys[0], 12);
        bchs[0][FEC25] = new s2_bch_engine_nf12(bch_polys[0], 12);
        bchs[0][FEC35] = new s2_bch_engine_nf12(bch_polys[0], 12);

        bchs[1][FEC12] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC23] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC34] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC56] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC45] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC89] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC14] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC13] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC25] = new s2_bch_engine_sf12(bch_polys[1], 12);
        bchs[1][FEC35] = new s2_bch_engine_sf12(bch_polys[1], 12);
    }

    ~s2_bch_engines()
    {
        for (int sf = 0; sf <= 1; ++sf)
        {
            for (int fec = 0; fec < FEC_COUNT; ++fec)
            {
                if (bchs[sf][fec]) {
                    delete bchs[sf][fec];
                }
            }
        }
    }
}; // s2_bch_engines

// S2 BASEBAND DESCRAMBLER AND FEC ENCODER
// EN 302 307-1 section 5.2.2
// EN 302 307-1 section 5.3

struct s2_fecenc : runnable
{
    typedef ldpc_engine<bool, hard_sb, 8, uint16_t> s2_ldpc_engine;

    s2_fecenc(
        scheduler *sch,
        pipebuf<bbframe> &_in,
        pipebuf<fecframe<hard_sb>> &_out
    ) :
        runnable(sch, "S2 fecenc"),
        in(_in),
        out(_out)
    {
        if (sch->debug) {
            s2ldpc.print_node_stats();
        }
    }

    void run()
    {
        while (in.readable() >= 1 && out.writable() >= 1)
        {
            run_frame(in.rd(), out.wr());
            in.read(1);
            out.written(1);
        }
    }

  private:
    void run_frame(const bbframe *pin, fecframe<hard_sb> *pout)
    {
        const modcod_info *mcinfo = check_modcod(pin->pls.modcod);
        const fec_info *fi = &fec_infos[pin->pls.sf][mcinfo->rate];
        pout->pls = pin->pls;
        hard_sb *pbytes = pout->bytes;
        bbscrambling.transform(pin->bytes, fi->Kbch / 8, pbytes);

        { // BCH
            size_t msgbytes = fi->Kbch / 8;
            bch_interface *bch = s2bch.bchs[pin->pls.sf][mcinfo->rate];
            bch->encode(pbytes, msgbytes, pbytes + msgbytes);
        }

        { // LDPC
            size_t msgbits = fi->kldpc;
            size_t cwbits = pin->pls.framebits();
            s2_ldpc_engine *ldpc = s2ldpc.ldpcs[pin->pls.sf][mcinfo->rate];
            ldpc->encode(fi->ldpc, pbytes, msgbits, cwbits, pbytes + msgbits / 8);
        }
    }

    pipereader<bbframe> in;
    pipewriter<fecframe<hard_sb>> out;
    s2_bbscrambling bbscrambling;
    s2_bch_engines s2bch;
    s2_ldpc_engines<bool, hard_sb> s2ldpc;
}; // s2_fecenc

// S2 FEC DECODER AND BASEBAND DESCRAMBLER
// EN 302 307-1 section 5.3
// EN 302 307-1 section 5.2.2

template <typename SOFTBIT, typename SOFTBYTE>
struct s2_fecdec : runnable
{
    int bitflips;

    s2_fecdec(
        scheduler *sch,
        pipebuf<fecframe<SOFTBYTE>> &_in, pipebuf<bbframe> &_out,
        pipebuf<int> *_bitcount = nullptr,
        pipebuf<int> *_errcount = nullptr
    ) :
        runnable(sch, "S2 fecdec"),
        bitflips(0),
        in(_in),
        out(_out),
        bitcount(opt_writer(_bitcount, 1)),
        errcount(opt_writer(_errcount, 1))
    {
        if (sch->debug) {
            s2ldpc.print_node_stats();
        }
    }

    void run()
    {
        while (in.readable() >= 1 && out.writable() >= 1 &&
               opt_writable(bitcount, 1) && opt_writable(errcount, 1))
        {
            fecframe<SOFTBYTE> *pin = in.rd();
            const modcod_info *mcinfo = check_modcod(pin->pls.modcod);
            const fec_info *fi = &fec_infos[pin->pls.sf][mcinfo->rate];
            bool corrupted = false;
            bool residual_errors;

            if (true)
            {
                // LDPC decode
                size_t cwbits = pin->pls.framebits();
                size_t msgbits = fi->kldpc;
                s2_ldpc_engine *ldpc = s2ldpc.ldpcs[pin->pls.sf][mcinfo->rate];
                int ncorr = ldpc->decode_bitflip(fi->ldpc, pin->bytes, msgbits, cwbits, bitflips);

                if (sch->debug2) {
                    fprintf(stderr, "LDPCCORR = %d\n", ncorr);
                }
            }

            uint8_t *hardbytes = softbytes_harden(pin->bytes, fi->kldpc / 8, bch_buf);

            if (true)
            {
                // BCH decode
                size_t cwbytes = fi->kldpc / 8;
                // Decode with suitable BCH decoder for this MODCOD
                bch_interface *bch = s2bch.bchs[pin->pls.sf][mcinfo->rate];
                int ncorr = bch->decode(hardbytes, cwbytes);

                if (sch->debug2) {
                    fprintf(stderr, "BCHCORR = %d\n", ncorr);
                }

                corrupted = (ncorr < 0);
                residual_errors = (ncorr != 0);

                // Report VER
                opt_write(bitcount, fi->Kbch);
                opt_write(errcount, (ncorr >= 0) ? ncorr : fi->Kbch);
            }

            int bbsize = fi->Kbch / 8;
            // TBD Some decoders want the bad packets.
#if 0
	if ( corrupted ) {
	  fprintf(stderr, "Passing bad frame\n");
	  corrupted = false;
	}
#endif
            if (!corrupted)
            {
                // Descramble and output
                bbframe *pout = out.wr();
                pout->pls = pin->pls;
                bbscrambling.transform(hardbytes, bbsize, pout->bytes);
                out.written(1);
            }

            if (sch->debug) {
                fprintf(stderr, "%c", corrupted ? ':' : residual_errors ? '.' : '_');
            }

            in.read(1);
        }
    }

  private:
    s2_ldpc_engines<SOFTBIT, SOFTBYTE> s2ldpc;
    uint8_t bch_buf[64800 / 8]; // Temp storage for hardening before BCH
    s2_bch_engines s2bch;
    s2_bbscrambling bbscrambling;
    pipereader<fecframe<SOFTBYTE>> in;
    pipewriter<bbframe> out;
    pipewriter<int> *bitcount, *errcount;
}; // s2_fecdec

#ifdef LINUX

// Soft LDPC decoder
// Internally implemented LDPC tool. Replaces external LDPC decoder

template <typename SOFTBIT, typename SOFTBYTE>
struct s2_fecdec_soft : runnable
{
    s2_fecdec_soft(
        scheduler *sch,
        pipebuf<fecframe<SOFTBYTE>> &_in,
        pipebuf<bbframe> &_out,
        int _modcod,
        bool _shortframes = true,
        int _max_trials = 25,
        pipebuf<int> *_bitcount = nullptr,
        pipebuf<int> *_errcount = nullptr
    ) :
        runnable(sch, "S2 fecdec soft"),
        in(_in),
        out(_out),
        modcod(_modcod < 0 ? 0 : _modcod > 31 ? 31 : _modcod),
        shortframes(_shortframes ? 1 : 0),
        max_trials(_max_trials),
        bitcount(opt_writer(_bitcount, 1)),
        errcount(opt_writer(_errcount, 1))
    {
        const char *tabname = ldpctool::LDPCInterface::mc_tabnames[shortframes][modcod];
        fprintf(stderr, "s2_fecdec_soft::s2_fecdec_soft: tabname: %s\n", tabname);

        if (tabname)
        {
            ldpc = ldpctool::create_ldpc((char *)"S2", tabname[0], atoi(tabname + 1));
            code = new ldpctool::code_type[ldpc->code_len()];
            aligned_buffer = aligned_alloc(sizeof(ldpctool::simd_type), sizeof(ldpctool::simd_type) * ldpc->code_len());
            simd = reinterpret_cast<ldpctool::simd_type *>(aligned_buffer);
        }
        else
        {
            ldpc = nullptr;
            aligned_buffer = nullptr;
            code = nullptr;
        }
    }

    ~s2_fecdec_soft()
    {
        if (ldpc) {
            delete ldpc;
        }
        if (aligned_buffer) {
            free(aligned_buffer);
        }
        if (code) {
            delete[] code;
        }
    }

    void run()
    {
        while (in.readable() >= 1 &&
            out.writable() >= 1 &&
            opt_writable(bitcount, 1) &&
            opt_writable(errcount, 1))
        {
            fecframe<SOFTBYTE> *pin = in.rd();
            const modcod_info *mcinfo = check_modcod(pin->pls.modcod);
            const fec_info *fi = &fec_infos[pin->pls.sf][mcinfo->rate];
            bool corrupted = false;
            bool residual_errors;

            if (ldpc)
            {
                decode.init(ldpc);
                int count = decode(simd, simd + ldpc->data_len(), max_trials, 1);

                if (count < 0) {
                    fprintf(stderr, "s2_fecdec_soft::run: decoder failed at converging to a code word in %d trials\n", max_trials);
                }

                for (int i = 0; i < ldpc->code_len(); ++i) {
                    code[i] = reinterpret_cast<ldpctool::code_type *>(simd + i)[0];
                }

                SOFTBYTE *ldpc_buf = reinterpret_cast<SOFTBYTE*>(code);
                uint8_t *hardbytes = softbytes_harden(ldpc_buf, fi->kldpc / 8, bch_buf);

                // BCH decode
                size_t cwbytes = fi->kldpc / 8;
                // Decode with suitable BCH decoder for this MODCOD
                bch_interface *bch = s2bch.bchs[pin->pls.sf][mcinfo->rate];
                int ncorr = bch->decode(hardbytes, cwbytes);

                if (sch->debug2) {
                    fprintf(stderr, "BCHCORR = %d\n", ncorr);
                }

                corrupted = (ncorr < 0);
                residual_errors = (ncorr != 0);
                // Report VER
                opt_write(bitcount, fi->Kbch);
                opt_write(errcount, (ncorr >= 0) ? ncorr : fi->Kbch);
                int bbsize = fi->Kbch / 8;

                if (!corrupted)
                {
                    // Descramble and output
                    bbframe *pout = out.wr();
                    pout->pls = pin->pls;
                    bbscrambling.transform(hardbytes, bbsize, pout->bytes);
                    out.written(1);
                }

                if (sch->debug) {
                    fprintf(stderr, "%c", corrupted ? ':' : residual_errors ? '.' : '_');
                }
            } // ldpc engine allocated

            in.read(1);
        }
    }

private:
    pipereader<fecframe<SOFTBYTE>> in;
    pipewriter<bbframe> out;
    int modcod;
    int shortframes;
    int max_trials;
    pipewriter<int> *bitcount, *errcount;

	typedef ldpctool::NormalUpdate<ldpctool::simd_type> update_type;
	//typedef SelfCorrectedUpdate<simd_type> update_type;

	//typedef MinSumAlgorithm<simd_type, update_type> algorithm_type;
	//typedef OffsetMinSumAlgorithm<simd_type, update_type, FACTOR> algorithm_type;
	typedef ldpctool::MinSumCAlgorithm<ldpctool::simd_type, update_type, ldpctool::FACTOR> algorithm_type;
	//typedef LogDomainSPA<simd_type, update_type> algorithm_type;
	//typedef LambdaMinAlgorithm<simd_type, update_type, 3> algorithm_type;
	//typedef SumProductAlgorithm<simd_type, update_type> algorithm_type;

	ldpctool::LDPCDecoder<ldpctool::simd_type, algorithm_type> decode;

    ldpctool::LDPCInterface *ldpc;
    ldpctool::code_type *code;
    void *aligned_buffer;
    ldpctool::simd_type *simd;
    uint8_t bch_buf[64800 / 8]; // Temp storage for hardening before BCH
    s2_bch_engines s2bch;
    s2_bbscrambling bbscrambling;
}; // s2_fecdec_soft

#endif

// External LDPC decoder
// Spawns a user-specified command, FEC frames on stdin/stdout.
template <typename T, int _SIZE>
struct simplequeue
{
    static const int SIZE = _SIZE;

    simplequeue()
    {
        rd = wr = count = 0;
    }

    bool full() { return count == SIZE; }

    T *put()
    {
        T *res = &q[wr];
        wr = (wr + 1) % SIZE;
        ++count;
        return res;
    }

    bool empty() { return count == 0; }
    const T *peek() { return &q[rd]; }

    const T *get()
    {
        const T *res = &q[rd];
        rd = (rd + 1) % SIZE;
        --count;
        return res;
    }

private:
    int rd, wr, count;
    T q[SIZE];
};

#if defined(USE_LDPC_TOOL) && !defined(_MSC_VER)

template <typename SOFTBIT, typename SOFTBYTE>
struct s2_fecdec_helper : runnable
{
    int batch_size;
    int nhelpers;
    bool must_buffer;
    int max_trials;

    s2_fecdec_helper(
        scheduler *sch,
        pipebuf<fecframe<SOFTBYTE>> &_in,
        pipebuf<bbframe> &_out,
        const char *_command,
        pipebuf<int> *_bitcount = nullptr,
        pipebuf<int> *_errcount = nullptr
    ) :
        runnable(sch, "S2 fecdec io"),
        batch_size(16),
        nhelpers(1),
        must_buffer(false),
        max_trials(8),
        in(_in),
        out(_out),
        bitcount(opt_writer(_bitcount, 1)),
        errcount(opt_writer(_errcount, 1))
    {
        command = strdup(_command);

        for (int mc = 0; mc < 32; ++mc) {
            for (int sf = 0; sf < 2; ++sf) {
                pools[mc][sf].procs = nullptr;
            }
        }
    }

    ~s2_fecdec_helper()
    {
        free(command);
        killall(); // also deletes pools[mc][sf].procs if necessary
    }

    void run()
    {
        // Send work until all helpers block.
        while (in.readable() >= 1 && !jobs.full())
        {
            if ((bbframe_q.size() != 0) && (out.writable() >= 1))
            {
                bbframe *pout = out.wr();
                pout->pls = bbframe_q.front().pls;
                std::copy(bbframe_q.front().bytes, bbframe_q.front().bytes + (58192 / 8), pout->bytes);
                bbframe_q.pop_front();
                out.written(1);
            }

            if ((bitcount_q.size() != 0) && opt_writable(bitcount, 1))
            {
                opt_write(bitcount, bitcount_q.front());
                bitcount_q.pop_front();
            }

            if ((errcount_q.size() != 0) && opt_writable(errcount, 1))
            {
                opt_write(errcount, errcount_q.front());
                errcount_q.pop_front();
            }

            if (!jobs.empty() && jobs.peek()->h->b_out) {
                receive_frame(jobs.get());
            }

            send_frame(in.rd());
            in.read(1);
        }
    }

  private:
    struct helper_instance
    {
        int fd_tx;      // To helper
        int fd_rx;      // From helper
        int batch_size; // Latency
        int b_in;       // Jobs in input queue
        int b_out;      // Jobs in output queue
        int pid;        // PID of the child
    };
    struct pool
    {
        helper_instance *procs; // nullptr or [nprocs]
        int nprocs;
        int shift;
    } pools[32][2]; // [modcod][sf]
    struct helper_job
    {
        s2_pls pls;
        helper_instance *h;
    };

    simplequeue<helper_job, 1024> jobs;

    // Try to send a frame. Return false if helper was busy.
    bool send_frame(fecframe<SOFTBYTE> *pin)
    {
        pool *p = get_pool(&pin->pls);

        for (int j = 0; j < p->nprocs; ++j)
        {
            int i = (p->shift + j) % p->nprocs;
            helper_instance *h = &p->procs[i];
            int iosize = (pin->pls.framebits() / 8) * sizeof(SOFTBYTE);
            // fprintf(stderr, "Writing %lu to fd %d\n", iosize, h->fd_tx);
            int nw = write(h->fd_tx, pin->bytes, iosize);

            if (nw < 0 && errno == EWOULDBLOCK)
            {
                //lseek(h->fd_tx, 0, SEEK_SET); // allow new writes on this worker
                //fprintf(stderr, "s2_fecdec_helper::send_frame: %d worker is busy\n", h->pid);
                continue; // next worker
            }

            if (nw < 0) {
                fatal("write(LDPC helper");
            } else if (nw != iosize) {
                fatal("partial write(LDPC helper)");
            }

            p->shift = i;
            helper_job *job = jobs.put();
            job->pls = pin->pls;
            job->h = h;
            ++h->b_in;

            if (h->b_in >= h->batch_size)
            {
                h->b_in -= h->batch_size;
                h->b_out += h->batch_size;
            }

            return true; // done sent to worker
        }

        fprintf(stderr, "s2_fecdec_helper::send_frame: WARNING: all %d workers were busy: modcod=%d sf=%d)\n",
            p->nprocs, pin->pls.modcod, pin->pls.sf);
        return false; // all workers were busy
    }

    // Return a pool of running helpers for a given modcod.
    pool *get_pool(const s2_pls *pls)
    {
        pool *p = &pools[pls->modcod][pls->sf];

        if (!p->procs)
        {
            fprintf(stderr, "s2_fecdec_helper::get_pool: allocate %d workers: modcod=%d sf=%d\n",
                nhelpers, pls->modcod, pls->sf);
            p->procs = new helper_instance[nhelpers];

            for (int i = 0; i < nhelpers; ++i) {
                spawn_helper(&p->procs[i], pls, i);
            }

            p->nprocs = nhelpers;
            p->shift = 0;
        }

        return p;
    }

    void killall()
    {
        fprintf(stderr, "s2_fecdec_helper::killall\n");

        for (int i = 0; i < 32; i++) // all MODCODs
        {
            for (int j = 0; j < 2; j++) // long and short frames
            {
                pool *p = &pools[i][j];

                if (p->procs)
                {
                    for (int i = 0; i < p->nprocs; ++i)
                    {
                        helper_instance *h = &p->procs[i];
                        fprintf(stderr, "s2_fecdec_helper::killall: killing %d\n", h->pid);
                        int rc = kill(h->pid, SIGKILL);

                        if (rc < 0)
                        {
                            fatal("s2_fecdec_helper::killall");
                        }
                        else
                        {
                            int cs;
                            waitpid(h->pid, &cs, 0);
                        }

                        // close pipes
                        close(h->fd_tx);
                        close(h->fd_rx);
                    }

                    delete p->procs;
                    p->procs = nullptr;
                    p->nprocs = 0;
                }
            } // long and short frames
        } // all MODCODs
    }

    // Spawn a helper process.
    void spawn_helper(helper_instance *h, const s2_pls *pls, imt)
    {
        if (sch->debug) {
            fprintf(stderr, "Spawning LDPC helper: modcod=%d sf=%d\n", pls->modcod, pls->sf);
        }

        int tx[2], rx[2];

        if (pipe(tx) || pipe(rx)) {
            fatal("pipe");
        }

        // Size the pipes so that the helper never runs out of work to do.
        int pipesize = 64800 * batch_size;
// macOS does not have F_SETPIPE_SZ and there
// is no way to change the buffer size
#ifndef __APPLE__
        long min_pipe_size = (long) fcntl(tx[0], F_GETPIPE_SZ);
        long pipe_size = (long) fcntl(rx[0], F_GETPIPE_SZ);
        min_pipe_size = std::min(min_pipe_size, pipe_size);
        pipe_size = (long) fcntl(tx[1], F_GETPIPE_SZ);
        min_pipe_size = std::min(min_pipe_size, pipe_size);
        pipe_size = (long) fcntl(rx[1], F_GETPIPE_SZ);
        min_pipe_size = std::min(min_pipe_size, pipe_size);

        if (min_pipe_size < pipesize)
        {
            if (fcntl(tx[0], F_SETPIPE_SZ, pipesize) < 0 ||
                fcntl(rx[0], F_SETPIPE_SZ, pipesize) < 0 ||
                fcntl(tx[1], F_SETPIPE_SZ, pipesize) < 0 ||
                fcntl(rx[1], F_SETPIPE_SZ, pipesize) < 0)
            {
                fprintf(stderr,
                        "*** Failed to increase pipe size from %ld.\n"
                        "*** Try echo %d > /proc/sys/fs/pipe-max-size\n",
                        min_pipe_size,
                        pipesize);

                if (must_buffer) {
                    fatal("F_SETPIPE_SZ");
                } else {
                    fprintf(stderr, "*** Throughput will be suboptimal.\n");
                }
            }
        }
#endif
        // vfork() differs from fork(2) in that the calling thread is
        // suspended until the child terminates
        int child = fork();

        if (!child)
        {
            // Child process
            close(tx[1]);
            dup2(tx[0], 0);
            close(rx[0]);
            dup2(rx[1], 1);
            char max_trials_arg[16];
            sprintf(max_trials_arg, "%d", max_trials);
            char batch_size_arg[16];
            sprintf(batch_size_arg, "%d", batch_size);
            char mc_arg[16];
            sprintf(mc_arg, "%d", pls->modcod);
            const char *sf_arg = pls->sf ? "--shortframes" : nullptr;
            const char *argv[] = {
                command,
                "--trials", max_trials_arg,
                "--batch-size", batch_size_arg,
                "--modcod", mc_arg,
                sf_arg,
                nullptr
            };
            execve(command, (char *const *)argv, nullptr);
            fatal(command);
        }

        h->pid = child;
        h->fd_tx = tx[1];
        close(tx[0]);
        h->fd_rx = rx[0];
        close(rx[1]);
        h->batch_size = batch_size; // TBD
        h->b_in = h->b_out = 0;
        int flags_tx = fcntl(h->fd_tx, F_GETFL);

        if (fcntl(h->fd_tx, F_SETFL, flags_tx | O_NONBLOCK)) {
            fatal("fcntl_tx(helper)");
        }

        int flags_rx = fcntl(h->fd_rx, F_GETFL);

        if (fcntl(h->fd_rx, F_SETFL, flags_rx | O_NONBLOCK)) {
            fatal("fcntl_rx(helper)");
        }
    }

    // Receive a finished job.
    void receive_frame(const helper_job *job)
    {
        // Read corrected frame from helper
        const s2_pls *pls = &job->pls;
        int iosize = (pls->framebits() / 8) * sizeof(ldpc_buf[0]);
        int nr = read(job->h->fd_rx, ldpc_buf, iosize);

        if (nr < 0)
        {
            if (errno != EAGAIN) { // if no data then try again next time
                fatal("s2_fecdec_helper::receive_frame read error");
            }
        }
        else if (nr != iosize)
        {
            fprintf(stderr, "s2_fecdec_helper::receive_frame: %d bytes read vs %d\n", nr, iosize);
        }

        --job->h->b_out;
        // Decode BCH.
        const modcod_info *mcinfo = check_modcod(job->pls.modcod);
        const fec_info *fi = &fec_infos[job->pls.sf][mcinfo->rate];
        uint8_t *hardbytes = softbytes_harden(ldpc_buf, fi->kldpc / 8, bch_buf);
        size_t cwbytes = fi->kldpc / 8;
        //size_t msgbytes = fi->Kbch / 8;
        //size_t chkbytes = cwbytes - msgbytes;
        bch_interface *bch = s2bch.bchs[job->pls.sf][mcinfo->rate];
        int ncorr = bch->decode(hardbytes, cwbytes);

        if (sch->debug2) {
            fprintf(stderr, "BCHCORR = %d\n", ncorr);
        }

        bool corrupted = (ncorr < 0);
        // Report VBER
        bitcount_q.push_back(fi->Kbch);
        //opt_write(bitcount, fi->Kbch);
        errcount_q.push_front((ncorr >= 0) ? ncorr : fi->Kbch);
        //opt_write(errcount, (ncorr >= 0) ? ncorr : fi->Kbch);
#if 0
      // TBD Some decoders want the bad packets.
	if ( corrupted ) {
	  fprintf(stderr, "Passing bad frame\n");
	  corrupted = false;
	}
#endif
        if (!corrupted)
        {
            // Descramble and output
            bbframe_q.emplace_back();
            //bbframe *pout = out.wr();
            bbframe_q.back().pls = job->pls;
            bbscrambling.transform(hardbytes, fi->Kbch / 8, bbframe_q.back().bytes);
            //out.written(1);
        }

        if (sch->debug) {
            fprintf(stderr, "%c", corrupted ? '!' : ncorr ? '.' : '_');
        }
    }

    pipereader<fecframe<SOFTBYTE>> in;
    pipewriter<bbframe> out;
    char *command;
    SOFTBYTE ldpc_buf[64800 / 8];
    uint8_t bch_buf[64800 / 8]; // Temp storage for hardening before BCH
    s2_bch_engines s2bch;
    s2_bbscrambling bbscrambling;
    std::deque<bbframe> bbframe_q;
    std::deque<int> bitcount_q;
    std::deque<int> errcount_q;
    pipewriter<int> *bitcount, *errcount;
}; // s2_fecdec_helper

#else // USE_LDPC_TOOL

template <typename SOFTBIT, typename SOFTBYTE>
struct s2_fecdec_helper : runnable
{
    int batch_size;
    int nhelpers;
    bool must_buffer;
    int max_trials;

    s2_fecdec_helper(
        scheduler *sch,
        pipebuf<fecframe<SOFTBYTE>> &_in,
        pipebuf<bbframe> &_out,
        const char *_command,
        pipebuf<int> *_bitcount = nullptr,
        pipebuf<int> *_errcount = nullptr
    ) :
        runnable(sch, "S2 fecdec io"),
        batch_size(32),
        nhelpers(1),
        must_buffer(false),
        max_trials(8),
        in(_in),
        out(_out),
        bitcount(opt_writer(_bitcount, 1)),
        errcount(opt_writer(_errcount, 1))
    {
        command = strdup(_command);

        for (int mc = 0; mc < 32; ++mc) {
            for (int sf = 0; sf < 2; ++sf) {
                pools[mc][sf].procs = nullptr;
            }
        }
    }

    ~s2_fecdec_helper()
    {
        free(command);
        killall(); // also deletes pools[mc][sf].procs if necessary
    }

    void run()
    {
        // Send work until all helpers block.
        while (in.readable() >= 1 && !jobs.full())
        {
            if ((bbframe_q.size() != 0) && (out.writable() >= 1))
            {
                bbframe *pout = out.wr();
                pout->pls = bbframe_q.front().pls;
                std::copy(bbframe_q.front().bytes, bbframe_q.front().bytes + (58192 / 8), pout->bytes);
                bbframe_q.pop_front();
                out.written(1);
            }

            if ((bitcount_q.size() != 0) && opt_writable(bitcount, 1))
            {
                opt_write(bitcount, bitcount_q.front());
                bitcount_q.pop_front();
            }

            if ((errcount_q.size() != 0) && opt_writable(errcount, 1))
            {
                opt_write(errcount, errcount_q.front());
                errcount_q.pop_front();
            }

            if (!jobs.empty() && jobs.peek()->h->b_out) {
                receive_frame(jobs.get());
            }

            send_frame(in.rd());
            in.read(1);
        }
    }

  private:
    struct helper_instance
    {
        QThread *m_thread;
        LDPCWorker *m_worker;
        int batch_size;
        int b_in;       // Jobs in input queue
        int b_out;      // Jobs in output queue
    };
    struct pool
    {
        helper_instance *procs; // nullptr or [nprocs]
        int nprocs;
        int shift;
    } pools[32][2]; // [modcod][sf]
    struct helper_job
    {
        s2_pls pls;
        helper_instance *h;
    };

    simplequeue<helper_job, 1024> jobs;

    // Try to send a frame. Return false if helper was busy.
    bool send_frame(fecframe<SOFTBYTE> *pin)
    {
        pool *p = get_pool(&pin->pls);

        for (int j = 0; j < p->nprocs; ++j)
        {
            int i = (p->shift + j) % p->nprocs;
            helper_instance *h = &p->procs[i];
            int iosize = (pin->pls.framebits() / 8) * sizeof(SOFTBYTE);

            if (h->m_worker->busy()) {
                continue;
            }

            QByteArray data((char *)pin->bytes, iosize);
            QMetaObject::invokeMethod(h->m_worker, "process", Qt::QueuedConnection, Q_ARG(QByteArray, data));

            p->shift = i;
            helper_job *job = jobs.put();
            job->pls = pin->pls;
            job->h = h;
            ++h->b_in;

            if (h->b_in >= h->batch_size)
            {
                h->b_in -= h->batch_size;
                h->b_out += h->batch_size;
            }

            return true; // done sent to worker
        }

        fprintf(stderr, "s2_fecdec_helper::send_frame: WARNING: all %d workers were busy: modcod=%d sf=%d)\n",
            p->nprocs, pin->pls.modcod, pin->pls.sf);
        return false; // all workers were busy
    }

    // Return a pool of running helpers for a given modcod.
    pool *get_pool(const s2_pls *pls)
    {
        pool *p = &pools[pls->modcod][pls->sf];

        if (!p->procs)
        {
            fprintf(stderr, "s2_fecdec_helper::get_pool: allocate %d workers: modcod=%d sf=%d\n",
                nhelpers, pls->modcod, pls->sf);
            p->procs = new helper_instance[nhelpers];

            for (int i = 0; i < nhelpers; ++i) {
                spawn_helper(&p->procs[i], pls, i);
            }

            p->nprocs = nhelpers;
            p->shift = 0;
        }

        return p;
    }

    void killall()
    {
        qDebug() << "s2_fecdec_helper::killall";

        for (int i = 0; i < 32; i++) // all MODCODs
        {
            for (int j = 0; j < 2; j++) // long and short frames
            {
                pool *p = &pools[i][j];

                if (p->procs)
                {
                    for (int i = 0; i < p->nprocs; ++i)
                    {
                        helper_instance *h = &p->procs[i];
                        h->m_thread->quit();
                        h->m_thread->wait();
                        delete h->m_thread;
                        h->m_thread = nullptr;
                        delete h->m_worker;
                        h->m_worker = nullptr;
                    }

                    delete p->procs;
                    p->procs = nullptr;
                    p->nprocs = 0;
                }
            } // long and short frames
        } // all MODCODs
    }

    // Spawn a helper thread.
    void spawn_helper(helper_instance *h, const s2_pls *pls, int helper_index)
    {
        qDebug() << "s2_fecdec_helper: Spawning LDPC thread: modcod=" << pls->modcod << " sf=" << pls->sf;
        h->m_thread = new QThread();
        h->m_thread->setObjectName(QString("ldpcDVBS2_%1").arg(helper_index));
        h->m_worker = new LDPCWorker(pls->modcod, max_trials, batch_size, pls->sf);
        h->m_worker->moveToThread(h->m_thread);
        h->batch_size = batch_size;
        h->b_in = h->b_out = 0;
        h->m_thread->start();
    }

    // Receive a finished job.
    void receive_frame(const helper_job *job)
    {
        // Non blocking read - will do the next time if no adata is available
        if (job->h->m_worker->dataAvailable())
        {
            QByteArray data = job->h->m_worker->data();
            memcpy(ldpc_buf, data.data(), data.size());
        }
        else
        {
            return;
        }

        --job->h->b_out;
        // Decode BCH.
        const modcod_info *mcinfo = check_modcod(job->pls.modcod);
        const fec_info *fi = &fec_infos[job->pls.sf][mcinfo->rate];
        uint8_t *hardbytes = softbytes_harden(ldpc_buf, fi->kldpc / 8, bch_buf);
        size_t cwbytes = fi->kldpc / 8;
        //size_t msgbytes = fi->Kbch / 8;
        //size_t chkbytes = cwbytes - msgbytes;
        bch_interface *bch = s2bch.bchs[job->pls.sf][mcinfo->rate];
        int ncorr = bch->decode(hardbytes, cwbytes);

        if (sch->debug2) {
            fprintf(stderr, "BCHCORR = %d\n", ncorr);
        }

        bool corrupted = (ncorr < 0);
        // Report VBER
        bitcount_q.push_back(fi->Kbch);
        //opt_write(bitcount, fi->Kbch);
        errcount_q.push_front((ncorr >= 0) ? ncorr : fi->Kbch);
        //opt_write(errcount, (ncorr >= 0) ? ncorr : fi->Kbch);
#if 0
      // TBD Some decoders want the bad packets.
	if ( corrupted ) {
	  fprintf(stderr, "Passing bad frame\n");
	  corrupted = false;
	}
#endif
        if (!corrupted)
        {
            // Descramble and output
            bbframe_q.emplace_back();
            //bbframe *pout = out.wr();
            bbframe_q.back().pls = job->pls;
            bbscrambling.transform(hardbytes, fi->Kbch / 8, bbframe_q.back().bytes);
            //out.written(1);
        }

        if (sch->debug) {
            fprintf(stderr, "%c", corrupted ? '!' : ncorr ? '.' : '_');
        }
    }

    pipereader<fecframe<SOFTBYTE>> in;
    pipewriter<bbframe> out;
    char *command;
    SOFTBYTE ldpc_buf[64800 / 8];
    uint8_t bch_buf[64800 / 8]; // Temp storage for hardening before BCH
    s2_bch_engines s2bch;
    s2_bbscrambling bbscrambling;
    std::deque<bbframe> bbframe_q;
    std::deque<int> bitcount_q;
    std::deque<int> errcount_q;
    pipewriter<int> *bitcount, *errcount;
}; // s2_fecdec_helper

#endif // USE_LDPC_TOOL

// S2 FRAMER
// EN 302 307-1 section 5.1 Mode adaptation

struct s2_framer : runnable
{
    uint8_t rolloff_code; // 0=0.35, 1=0.25, 2=0.20, 3=reserved
    // User must provide pls_seq[n_pls_seq].
    // For ACM, user can change pls_seq[0] at runtime.
    // For VCM with a repeating pattern, use n_pls_seq>=2.
    s2_pls *pls_seq;
    int n_pls_seq;


    s2_framer(
        scheduler *sch,
        pipebuf<tspacket> &_in,
        pipebuf<bbframe> &_out
    ) :
        runnable(sch, "S2 framer"),
    	n_pls_seq(0),
	    pls_index(0),
        in(_in),
        out(_out)
    {
        nremain = 0;
        remcrc = 0; // CRC for nonexistent previous packet
    }

    void run()
    {
        while (out.writable() >= 1)
        {
            if (!n_pls_seq ) {
                fail("PLS not specified");
            }

            s2_pls *pls = &pls_seq[pls_index];
            const modcod_info *mcinfo = check_modcod(pls->modcod);
            const fec_info *fi = &fec_infos[pls->sf][mcinfo->rate];
            int framebytes = fi->Kbch / 8;

            if (!framebytes) {
                fail("MODCOD/framesize combination not allowed");
            }

            if (10 + nremain + 188 * in.readable() < framebytes) {
                break; // Not enough data to fill a frame
            }

            bbframe *pout = out.wr();
            pout->pls = *pls;
            uint8_t *buf = pout->bytes;
            uint8_t *end = buf + framebytes;
            // EN 302 307-1 section 5.1.6 Base-Band Header insertion
            uint8_t *bbheader = buf;
            uint8_t matype1 = 0;
            matype1 |= 0xc0;  // TS
            matype1 |= 0x20;  // SIS
            matype1 |= (n_pls_seq==1) ? 0x10 : 0x00;  // CCM/ACM
            // TBD ISSY/NPD required for ACM ?
            matype1 |= rolloff_code;
            *buf++ = matype1;             // MATYPE-1
            *buf++ = 0;                   // MATYPE-2
            uint16_t upl = 188 * 8;
            *buf++ = upl >> 8; // UPL MSB
            *buf++ = upl;      // UPL LSB
            uint16_t dfl = (framebytes - 10) * 8;
            *buf++ = dfl >> 8; // DFL MSB
            *buf++ = dfl;      // DFL LSB
            *buf++ = 0x47;     // SYNC
            uint16_t syncd = nremain * 8;
            *buf++ = syncd >> 8; // SYNCD MSB
            *buf++ = syncd;      // SYNCD LSB
            *buf++ = crc8.compute(bbheader, 9);
            // Data field
            memcpy(buf, rembuf, nremain); // Leftover from previous runs
            buf += nremain;

            while (buf < end)
            {
                tspacket *tsp = in.rd();

                if (tsp->data[0] != MPEG_SYNC) {
                    fail("Invalid TS");
                }

                *buf++ = remcrc; // Replace SYNC with CRC of previous.
                remcrc = crc8.compute(tsp->data + 1, tspacket::SIZE - 1);
                int nused = end - buf;

                if (nused > tspacket::SIZE - 1) {
                    nused = tspacket::SIZE - 1;
                }

                memcpy(buf, tsp->data + 1, nused);
                buf += nused;

                if (buf == end)
                {
                    nremain = (tspacket::SIZE - 1) - nused;
                    memcpy(rembuf, tsp->data + 1 + nused, nremain);
                }

                in.read(1);
            }

            if (buf != end) {
                fail("Bug: s2_framer");
            }

            out.written(1);
	        ++pls_index;

	        if (pls_index == n_pls_seq) {
                pls_index = 0;
            }
        }
    }

private:
    int pls_index; // Next slot to use in pls_seq
    pipereader<tspacket> in;
    pipewriter<bbframe> out;
    crc8_engine crc8;
    int nremain;
    uint8_t rembuf[tspacket::SIZE];
    uint8_t remcrc;
}; // s2_framer

// S2 DEFRAMER
// EN 302 307-1 section 5.1 Mode adaptation

struct s2_deframer : runnable
{
    int fd_gse; // FD for generic streams, or -1

    s2_deframer(
        scheduler *sch,
        pipebuf<bbframe> &_in,
        pipebuf<tspacket> &_out,
        pipebuf<int> *_state_out = nullptr,
        pipebuf<unsigned long> *_locktime_out = nullptr
    ) :
        runnable(sch, "S2 deframer"),
        fd_gse(-1),
        nleftover(-1),
        in(_in),
        out(_out, MAX_TS_PER_BBFRAME),
        current_state(false),
        state_out(opt_writer(_state_out, 2)),
        report_state(true),
        locktime(0),
        locktime_out(opt_writer(_locktime_out, MAX_TS_PER_BBFRAME))
    {
    }

    void run()
    {
        while (in.readable() >= 1 && out.writable() >= MAX_TS_PER_BBFRAME &&
               opt_writable(state_out, 2) &&
               opt_writable(locktime_out, MAX_TS_PER_BBFRAME))
        {
            if (report_state)
            {
                // Report unlocked state on first invocation.
                opt_write(state_out, 0);
                report_state = false;
            }

            run_bbframe(in.rd());
            in.read(1);
        }
    }

private:
    void run_bbframe(bbframe *pin)
    {
        uint8_t *bbh = pin->bytes;
        // EN 302 307 section 5.1.6 Base-Band Header Insertion
        uint8_t streamtype = bbh[0] >> 6;
        bool sis = bbh[0] & 32;
        bool ccm = bbh[0] & 16;
        bool issyi = bbh[0] & 8;
        bool npd = bbh[0] & 4;
        int ro_code = bbh[0] & 3;
        uint8_t isi = bbh[1];  // if !sis
        uint16_t upl = (bbh[2] << 8) | bbh[3];
        uint16_t dfl = (bbh[4] << 8) | bbh[5];
        uint8_t sync = bbh[6];
        uint16_t syncd = (bbh[7] << 8) | bbh[8];
        uint8_t crcexp = crc8.compute(bbh, 9);
        uint8_t crc = bbh[9];
        uint8_t *data = bbh + 10;

        if (sch->debug2)
        {
            static const char *stnames[] = { "GP", "GC", "??", "TS" };
            static float ro_values[] = {0.35, 0.25, 0.20, 0};
            fprintf(stderr, "BBH: crc %02x/%02x(%s) %s %s(ISI=%d) %s%s%s ro=%.2f"
                " upl=%d dfl=%d sync=%02x syncd=%d\n",
                crc,
                crcexp,
                (crc == crcexp) ? "OK" : "KO",
                stnames[streamtype],
                (sis ? "SIS" : "MIS"),
                isi,
                (ccm ? "CCM" : "ACM"),
                (issyi ? " ISSYI": ""),
                (npd ? " NPD" : ""),
                ro_values[ro_code],
                upl,
                dfl,
                sync,
                syncd
            );
        }

        if (crc != crcexp || dfl > fec_info::KBCH_MAX)
        {
            // Note: Maybe accept syncd=65535
            if (sch->debug) {
                fprintf(stderr, "Bad bbframe\n");
            }

            nleftover = -1;
            info_unlocked();
            return; // Max one state_out per loop
        }

        // TBD: Supporting byte-oriented payloads only.
        if ((dfl&7) || (syncd&7))
        {
            fprintf(stderr, "Unsupported bbframe\n");
            nleftover = -1;
            info_unlocked();
            return; // Max one state_out per loop
        }

        if (streamtype==3 && upl==188*8 && sync==0x47 && syncd<=dfl)
        {
	        handle_ts(data, dfl, syncd, sync);
        }
        else if (streamtype == 1)
        {
            if (fd_gse >= 0)
            {
                ssize_t nw = write(fd_gse, data, dfl/8);

                if (nw < 0) {
                    fatal("write(gse)");
                }

                if (nw != dfl/8) {
                    fail("partial write(gse");
                }
            }
            else
            {
                fprintf(stderr, "Unrecognized bbframe\n");
            }
        }
    }

    void handle_ts(uint8_t *data, uint16_t dfl, uint16_t syncd, uint8_t sync)
    {
        int pos; // Start of useful data in this bbframe

        if (nleftover < 0)
        {
            // Not synced. Skip unusable data at beginning of bbframe
            pos = syncd / 8;

            if (sch->debug) {
                fprintf(stderr, "Start TS at %d\n", pos);
            }

            nleftover = 0;
        }
        else
        {
            // Sanity check
            if (syncd / 8 != 188 - nleftover)
            {
                if (sch->debug) {
                    fprintf(stderr, "Lost a bbframe ?\n");
                }

                nleftover = -1;
                info_unlocked();
                return; // Max one state_out per loop
            }
            pos = 0;
        }

        while ( pos+(188-nleftover)+1 <= dfl/8 )
        {
            // Enough data available for one packet and its CRC.
            tspacket *pout = out.wr();
            memcpy(pout->data, leftover, nleftover);  // NOP most of the time
            memcpy(pout->data+nleftover, data+pos, 188-nleftover);
            pout->data[0] = sync; // Replace CRC
            uint8_t crc = crc8.compute(pout->data+1, 188-1);

            if (data[pos+(188-nleftover)] == crc)
            {
                info_good_packet();
            }
            else
            {
                pout->data[1] |= 0x80;  // Set TEI bit

                if (sch->debug) {
                    fprintf(stderr, "C");
                }
            }

            out.written(1);
            pos += 188 - nleftover;
            nleftover = 0;
        }

        int remain = dfl / 8 - pos;

        if (nleftover + remain > (int) sizeof(leftover)) {
            fail("Bug: TS deframer");
        }

        memcpy(leftover+nleftover, data+pos, remain);
        nleftover += remain;
    }

    void info_unlocked()
    {
        info_is_locked(false);
        locktime = 0;
    }

    void info_good_packet()
    {
        info_is_locked(true);
        ++locktime;
        opt_write(locktime_out, locktime);
    }

    void info_is_locked(bool newstate)
    {
        if (newstate != current_state)
        {
            opt_write(state_out, newstate ? 1 : 0);
            current_state = newstate;
        }
    }

    crc8_engine crc8;
    int nleftover;  // Bytes in leftover[]:
                    // -1      = not synced.
                    // 0       = no leftover data
                    // 1 - 187 = incomplete packet
                    // 188     =  waiting for CRC
    uint8_t leftover[188];
    static const int MAX_TS_PER_BBFRAME = fec_info::KBCH_MAX / 8 / 188 + 1;
    pipereader<bbframe> in;
    pipewriter<tspacket> out;
    int current_state;
    pipewriter<int> *state_out;
    bool report_state;
    unsigned long locktime;
    pipewriter<unsigned long> *locktime_out;
}; // s2_deframer

} // namespace leansdr

#endif // LEANSDR_DVBS2_H