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

#ifndef LEANSDR_SDR_H
#define LEANSDR_SDR_H

#include "leansdr/math.h"
#include "leansdr/dsp.h"
#include "leansdr/incrementalarray.h"

namespace leansdr
{

// Abbreviations for floating-point types

typedef float f32;

typedef complex<u8> cu8;
typedef complex<s8> cs8;
typedef complex<u16> cu16;
typedef complex<s16> cs16;
typedef complex<f32> cf32;

//////////////////////////////////////////////////////////////////////
// SDR blocks
//////////////////////////////////////////////////////////////////////

// AUTO-NOTCH FILTER

// Periodically detects the [n__slots] strongest peaks with a FFT,
// removes them with a first-order filter.

template<typename T>
struct auto_notch: runnable
{
    int decimation;
    float k;

    auto_notch(scheduler *sch, pipebuf<complex<T> > &_in, pipebuf<complex<T> > &_out, int _n__slots, T _agc_rms_setpoint) :
            runnable(sch, "auto_notch"),
            decimation(1024 * 4096),
            k(0.002), // k(0.01)
            fft(4096),
            in(_in),
            out(_out, fft.n),
            n__slots(_n__slots),
            __slots(new slot[n__slots]),
            phase(0),
            gain(1),
            agc_rms_setpoint(_agc_rms_setpoint)
    {
        for (int s = 0; s < n__slots; ++s)
        {
            __slots[s].i = -1;
            __slots[s].expj = new complex<float> [fft.n];
        }
        m_data.allocate(fft.n);
        m_amp.allocate(fft.n);
    }

    void run()
    {
        while (in.readable() >= fft.n && out.writable() >= fft.n)
        {
            phase += fft.n;
            if (phase >= decimation)
            {
                phase -= decimation;
                detect();
            }
            process();
            in.read(fft.n);
            out.written(fft.n);
        }
    }

    void detect()
    {
        complex<T> *pin = in.rd();
        //complex<float> data[fft.n];
        complex<float> *data = m_data.m_array;
        float m0 = 0, m2 = 0;

        for (unsigned int i = 0; i < fft.n; ++i)
        {
            data[i].re = pin[i].re;
            data[i].im = pin[i].im;
            m2 += (float) pin[i].re * pin[i].re + (float) pin[i].im * pin[i].im;
            if (gen_abs(pin[i].re) > m0)
                m0 = gen_abs(pin[i].re);
            if (gen_abs(pin[i].im) > m0)
                m0 = gen_abs(pin[i].im);
        }

        if (agc_rms_setpoint && m2)
        {
            float rms = gen_sqrt(m2 / fft.n);
            if (sch->debug)
                fprintf(stderr, "(pow %f max %f)", rms, m0);
            float new_gain = agc_rms_setpoint / rms;
            gain = gain * 0.9 + new_gain * 0.1;
        }

        fft.inplace(data, true);
        //float amp[fft.n];
        float *amp = m_amp.m_array;

        for (unsigned int i = 0; i < fft.n; ++i) {
            amp[i] = hypotf(data[i].re, data[i].im);
        }

        for (slot *s = __slots; s < __slots + n__slots; ++s)
        {
            int iamax = 0;
            for (unsigned int i = 0; i < fft.n; ++i)
            {
                if (amp[i] > amp[iamax]) {
                    iamax = i;
                }
            }
            if (iamax != s->i)
            {
                if (sch->debug)
                    fprintf(stderr, "%s: slot %d new peak %d -> %d\n", name,
                            (int) (s - __slots), s->i, iamax);
                s->i = iamax;
                s->estim.re = 0;
                s->estim.im = 0;
                s->estt = 0;
                for (unsigned int i = 0; i < fft.n; ++i)
                {
                    float a = 2 * M_PI * s->i * i / fft.n;
                    s->expj[i].re = cosf(a);
                    s->expj[i].im = sinf(a);
                }
            }
            amp[iamax] = 0;
            if (iamax - 1 >= 0) {
                amp[iamax - 1] = 0;
            }
            if (iamax + 1 < (int) fft.n) {
                amp[iamax + 1] = 0;
            }
        }
    }

    void process()
    {
        complex<T> *pin = in.rd(), *pend = pin + fft.n, *pout = out.wr();
        for (slot *s = __slots; s < __slots + n__slots; ++s)
            s->ej = s->expj;
        for (; pin < pend; ++pin, ++pout)
        {
            complex<float> out = *pin;
            // TODO Optimize for n__slots==1 ?
            for (slot *s = __slots; s < __slots + n__slots; ++s->ej, ++s)
            {
                complex<float> bb(pin->re * s->ej->re + pin->im * s->ej->im,
                        -pin->re * s->ej->im + pin->im * s->ej->re);
                s->estim.re = bb.re * k + s->estim.re * (1 - k);
                s->estim.im = bb.im * k + s->estim.im * (1 - k);
                complex<float> sub(
                        s->estim.re * s->ej->re - s->estim.im * s->ej->im,
                        s->estim.re * s->ej->im + s->estim.im * s->ej->re);
                out.re -= sub.re;
                out.im -= sub.im;
            }
            pout->re = gain * out.re;
            pout->im = gain * out.im;
        }
    }

private:
    cfft_engine<float> fft;
    pipereader<complex<T> > in;
    pipewriter<complex<T> > out;
    int n__slots;

    struct slot
    {
        int i;
        complex<float> estim;
        complex<float> *expj, *ej;
        int estt;
    }*__slots;

    int phase;
    float gain;
    T agc_rms_setpoint;
    IncrementalArray<complex<float> > m_data;
    IncrementalArray<float> m_amp;
};

// SIGNAL STRENGTH ESTIMATOR

// Outputs RMS values.

template<typename T>
struct ss_estimator: runnable
{
    unsigned long window_size;  // Samples per estimation
    unsigned long decimation;  // Output rate

    ss_estimator(scheduler *sch, pipebuf<complex<T> > &_in, pipebuf<T> &_out) :
            runnable(sch, "SS estimator"),
            window_size(1024),
            decimation(1024),
            in(_in),
            out(_out),
            phase(0)
    {
    }

    void run()
    {
        while (in.readable() >= window_size && out.writable() >= 1)
        {
            phase += window_size;
            if (phase >= decimation)
            {
                phase -= decimation;
                complex<T> *p = in.rd(), *pend = p + window_size;
                float s = 0;
                for (; p < pend; ++p)
                    s += (float) p->re * p->re + (float) p->im * p->im;
                out.write(sqrtf(s / window_size));
            }
            in.read(window_size);
        }
    }

private:
    pipereader<complex<T> > in;
    pipewriter<T> out;
    unsigned long phase;
};

template<typename T>
struct ss_amp_estimator: runnable
{
    unsigned long window_size;  // Samples per estimation
    unsigned long decimation;  // Output rate

    ss_amp_estimator(scheduler *sch, pipebuf<complex<T> > &_in, pipebuf<T> &_out_ss, pipebuf<T> &_out_ampmin, pipebuf<T> &_out_ampmax) :
            runnable(sch, "SS estimator"),
            window_size(1024),
            decimation(1024),
            in(_in),
            out_ss(_out_ss),
            out_ampmin(_out_ampmin),
            out_ampmax(_out_ampmax),
            phase(0)
    {
    }

    void run()
    {
        while (in.readable() >= window_size && out_ss.writable() >= 1
                && out_ampmin.writable() >= 1 && out_ampmax.writable() >= 1)
        {
            phase += window_size;
            if (phase >= decimation)
            {
                phase -= decimation;
                complex<T> *p = in.rd(), *pend = p + window_size;
                float s2 = 0;
                float amin = 1e38, amax = 0;
                for (; p < pend; ++p)
                {
                    float mag2 = (float) p->re * p->re + (float) p->im * p->im;
                    s2 += mag2;
                    float mag = sqrtf(mag2);
                    if (mag < amin)
                        amin = mag;
                    if (mag > amax)
                        amax = mag;
                }
                out_ss.write(sqrtf(s2 / window_size));
                out_ampmin.write(amin);
                out_ampmax.write(amax);
            }
            in.read(window_size);
        }
    }

private:
    pipereader<complex<T> > in;
    pipewriter<T> out_ss, out_ampmin, out_ampmax;
    unsigned long phase;
};

// AGC

template<typename T>
struct simple_agc: runnable
{
    float out_rms;    // Desired RMS output power
    float bw;         // Bandwidth
    float estimated;  // Input power

    simple_agc(scheduler *sch, pipebuf<complex<T> > &_in, pipebuf<complex<T> > &_out) :
            runnable(sch, "AGC"),
            out_rms(1),
            bw(0.001),
            estimated(0),
            in(_in),
            out(_out)
    {
    }

private:
    pipereader<complex<T> > in;
    pipewriter<complex<T> > out;
    static const int chunk_size = 128;

    void run()
    {
        while (in.readable() >= chunk_size && out.writable() >= chunk_size)
        {
            complex<T> *pin = in.rd(), *pend = pin + chunk_size;
            float amp2 = 0;
            for (; pin < pend; ++pin)
                amp2 += pin->re * pin->re + pin->im * pin->im;
            amp2 /= chunk_size;
            if (!estimated)
                estimated = amp2;
            estimated = estimated * (1 - bw) + amp2 * bw;
            float gain = estimated ? out_rms / sqrtf(estimated) : 0;
            pin = in.rd();
            complex<T> *pout = out.wr();
            for (; pin < pend; ++pin, ++pout)
            {
                pout->re = pin->re * gain;
                pout->im = pin->im * gain;
            }
            in.read(chunk_size);
            out.written(chunk_size);
        }
    }
};
// simple_agc

typedef uint16_t u_angle;  //  [0,2PI[ in 65536 steps
typedef int16_t s_angle;  // [-PI,PI[ in 65536 steps

// GENERIC CONSTELLATION DECODING BY LOOK-UP TABLE.

// Metrics and phase errors are pre-computed on a RxR grid.
// R must be a power of 2.
// Up to 256 symbols.

struct softsymbol
{
    int16_t cost;  // For Viterbi with TBM=int16_t
    uint8_t symbol;
};

// Target RMS amplitude for AGC
//const float cstln_amp = 73;  // Best for 32APSK 9/10
//const float cstln_amp = 90;  // Best for QPSK
//const float cstln_amp = 64;  // Best for BPSK
//const float cstln_amp = 75;  // Best for BPSK at 45°
const float cstln_amp = 75;  // Trade-off

template<int R>
struct cstln_lut
{
    complex<signed char> *symbols;
    int nsymbols;
    int nrotations;

    enum predef
    {
        BPSK,                    // DVB-S2 (and DVB-S variant)
        QPSK,                    // DVB-S
        PSK8,
        APSK16,
        APSK32,    // DVB-S2
        APSK64E,                 // DVB-S2X
        QAM16,
        QAM64,
        QAM256     // For experimentation only
    };

    cstln_lut(predef type, float gamma1 = 1, float gamma2 = 1, float gamma3 = 1)
    {
        switch (type)
        {
        case BPSK:
            nrotations = 2;
            nsymbols = 2;
            symbols = new complex<signed char> [nsymbols];
#if 0  // BPSK at 0°
            symbols[0] = polar(1, 2, 0);
            symbols[1] = polar(1, 2, 1);
#else  // BPSK at 45°
            symbols[0] = polar(1, 8, 1);
            symbols[1] = polar(1, 8, 5);
#endif
            make_lut_from_symbols();
            break;
        case QPSK:
            // EN 300 421, section 4.5 Baseband shaping and modulation
            // EN 302 307, section 5.4.1
            nrotations = 4;
            nsymbols = 4;
            symbols = new complex<signed char> [nsymbols];
            symbols[0] = polar(1, 4, 0.5);
            symbols[1] = polar(1, 4, 3.5);
            symbols[2] = polar(1, 4, 1.5);
            symbols[3] = polar(1, 4, 2.5);
            make_lut_from_symbols();
            break;
        case PSK8:
            // EN 302 307, section 5.4.2
            nrotations = 8;
            nsymbols = 8;
            symbols = new complex<signed char> [nsymbols];
            symbols[0] = polar(1, 8, 1);
            symbols[1] = polar(1, 8, 0);
            symbols[2] = polar(1, 8, 4);
            symbols[3] = polar(1, 8, 5);
            symbols[4] = polar(1, 8, 2);
            symbols[5] = polar(1, 8, 7);
            symbols[6] = polar(1, 8, 3);
            symbols[7] = polar(1, 8, 6);
            make_lut_from_symbols();
            break;
        case APSK16:
        {
            // EN 302 307, section 5.4.3
            float r1 = sqrtf(4 / (1 + 3 * gamma1 * gamma1));
            float r2 = gamma1 * r1;
            nrotations = 4;
            nsymbols = 16;
            symbols = new complex<signed char> [nsymbols];
            symbols[0] = polar(r2, 12, 1.5);
            symbols[1] = polar(r2, 12, 10.5);
            symbols[2] = polar(r2, 12, 4.5);
            symbols[3] = polar(r2, 12, 7.5);
            symbols[4] = polar(r2, 12, 0.5);
            symbols[5] = polar(r2, 12, 11.5);
            symbols[6] = polar(r2, 12, 5.5);
            symbols[7] = polar(r2, 12, 6.5);
            symbols[8] = polar(r2, 12, 2.5);
            symbols[9] = polar(r2, 12, 9.5);
            symbols[10] = polar(r2, 12, 3.5);
            symbols[11] = polar(r2, 12, 8.5);
            symbols[12] = polar(r1, 4, 0.5);
            symbols[13] = polar(r1, 4, 3.5);
            symbols[14] = polar(r1, 4, 1.5);
            symbols[15] = polar(r1, 4, 2.5);
            make_lut_from_symbols();
            break;
        }
        case APSK32:
        {
            // EN 302 307, section 5.4.3
            float r1 = sqrtf(
                    8 / (1 + 3 * gamma1 * gamma1 + 4 * gamma2 * gamma2));
            float r2 = gamma1 * r1;
            float r3 = gamma2 * r1;
            nrotations = 4;
            nsymbols = 32;
            symbols = new complex<signed char> [nsymbols];
            symbols[0] = polar(r2, 12, 1.5);
            symbols[1] = polar(r2, 12, 2.5);
            symbols[2] = polar(r2, 12, 10.5);
            symbols[3] = polar(r2, 12, 9.5);
            symbols[4] = polar(r2, 12, 4.5);
            symbols[5] = polar(r2, 12, 3.5);
            symbols[6] = polar(r2, 12, 7.5);
            symbols[7] = polar(r2, 12, 8.5);
            symbols[8] = polar(r3, 16, 1);
            symbols[9] = polar(r3, 16, 3);
            symbols[10] = polar(r3, 16, 14);
            symbols[11] = polar(r3, 16, 12);
            symbols[12] = polar(r3, 16, 6);
            symbols[13] = polar(r3, 16, 4);
            symbols[14] = polar(r3, 16, 9);
            symbols[15] = polar(r3, 16, 11);
            symbols[16] = polar(r2, 12, 0.5);
            symbols[17] = polar(r1, 4, 0.5);
            symbols[18] = polar(r2, 12, 11.5);
            symbols[19] = polar(r1, 4, 3.5);
            symbols[20] = polar(r2, 12, 5.5);
            symbols[21] = polar(r1, 4, 1.5);
            symbols[22] = polar(r2, 12, 6.5);
            symbols[23] = polar(r1, 4, 2.5);
            symbols[24] = polar(r3, 16, 0);
            symbols[25] = polar(r3, 16, 2);
            symbols[26] = polar(r3, 16, 15);
            symbols[27] = polar(r3, 16, 13);
            symbols[28] = polar(r3, 16, 7);
            symbols[29] = polar(r3, 16, 5);
            symbols[30] = polar(r3, 16, 8);
            symbols[31] = polar(r3, 16, 10);
            make_lut_from_symbols();
            break;
        }
        case APSK64E:
        {
            // EN 302 307-2, section 5.4.5, Table 13e
            float r1 = sqrtf(
                    64
                            / (4 + 12 * gamma1 * gamma1 + 20 * gamma2 * gamma2
                                    + 28 * gamma3 * gamma3));
            float r2 = gamma1 * r1;
            float r3 = gamma2 * r1;
            float r4 = gamma3 * r1;
            nrotations = 4;
            nsymbols = 64;
            symbols = new complex<signed char> [nsymbols];
            polar2(0, r4, 1.0 / 4, 7.0 / 4, 3.0 / 4, 5.0 / 4);
            polar2(4, r4, 13.0 / 28, 43.0 / 28, 15.0 / 28, 41.0 / 28);
            polar2(8, r4, 1.0 / 28, 55.0 / 28, 27.0 / 28, 29.0 / 28);
            polar2(12, r1, 1.0 / 4, 7.0 / 4, 3.0 / 4, 5.0 / 4);
            polar2(16, r4, 9.0 / 28, 47.0 / 28, 19.0 / 28, 37.0 / 28);
            polar2(20, r4, 11.0 / 28, 45.0 / 28, 17.0 / 28, 39.0 / 28);
            polar2(24, r3, 1.0 / 20, 39.0 / 20, 19.0 / 20, 21.0 / 20);
            polar2(28, r2, 1.0 / 12, 23.0 / 12, 11.0 / 12, 13.0 / 12);
            polar2(32, r4, 5.0 / 28, 51.0 / 28, 23.0 / 28, 33.0 / 28);
            polar2(36, r3, 9.0 / 20, 31.0 / 20, 11.0 / 20, 29.0 / 20);
            polar2(40, r4, 3.0 / 28, 53.0 / 28, 25.0 / 28, 31.0 / 28);
            polar2(44, r2, 5.0 / 12, 19.0 / 12, 7.0 / 12, 17.0 / 12);
            polar2(48, r3, 1.0 / 4, 7.0 / 4, 3.0 / 4, 5.0 / 4);
            polar2(52, r3, 7.0 / 20, 33.0 / 20, 13.0 / 20, 27.0 / 20);
            polar2(56, r3, 3.0 / 20, 37.0 / 20, 17.0 / 20, 23.0 / 20);
            polar2(60, r2, 1.0 / 4, 7.0 / 4, 3.0 / 4, 5.0 / 4);
            make_lut_from_symbols();
            break;
        }
        case QAM16:
            make_qam(16);
            break;
        case QAM64:
            make_qam(64);
            break;
        case QAM256:
            make_qam(256);
            break;
        default:
            fail("cstln_lut::cstln_lut", "Constellation not implemented");
            return;
        }
    }
    struct result
    {
        struct softsymbol ss;
        s_angle phase_error;
    };
    inline result *lookup(float I, float Q)
    {
        // Handling of overflows beyond the lookup table:
        // - For BPSK/QPSK/8PSK we only care about the phase,
        //   so the following is harmless and improves locking at low SNR.
        // - For amplitude modulations this is not appropriate.
        //   However, if there is enough noise to cause overflow,
        //   demodulation would probably fail anyway.
        //
        // Comment-out for better throughput at high SNR.
#if 1
        while (I < -128 || I > 127 || Q < -128 || Q > 127)
        {
            I *= 0.5;
            Q *= 0.5;
        }
#endif
        return &lut[(u8) (s8) I][(u8) (s8) Q];
    }

    inline result *lookup(int I, int Q)
    {
        // Ignore wrapping modulo 256
        return &lut[(u8) I][(u8) Q];
    }

private:
    complex<signed char> polar(float r, int n, float i)
    {
        float a = i * 2 * M_PI / n;
        return complex<signed char>(r * cosf(a) * cstln_amp,
                r * sinf(a) * cstln_amp);
    }

    // Helper function for some constellation tables
    void polar2(int i, float r, float a0, float a1, float a2, float a3)
    {
        float a[] =
        { a0, a1, a2, a3 };
        for (int j = 0; j < 4; ++j)
        {
            float phi = a[j] * M_PI;
            symbols[i + j] = complex<signed char>(r * cosf(phi) * cstln_amp,
                    r * sinf(phi) * cstln_amp);
        }
    }

    void make_qam(int n)
    {
        nrotations = 4;
        nsymbols = n;
        symbols = new complex<signed char> [nsymbols];
        int m = sqrtl(n);
        float scale;
        { // Average power in first quadrant with unit grid
            int q = m / 2;
            float avgpower = 2
                    * (q * 0.25 + (q - 1) * (q / 2)
                            + (q - 1) * q * (2 * q - 1) / 6) / q;
            scale = 1.0 / sqrtf(avgpower);
        }
        // Arbitrary mapping
        int s = 0;
        for (int x = 0; x < m; ++x)
            for (int y = 0; y < m; ++y)
            {
                float I = x - (float) (m - 1) / 2;
                float Q = y - (float) (m - 1) / 2;
                symbols[s].re = I * scale * cstln_amp;
                symbols[s].im = Q * scale * cstln_amp;
                ++s;
            }
        make_lut_from_symbols();
    }

    result lut[R][R];

    void make_lut_from_symbols()
    {
        for (int I = -R / 2; I < R / 2; ++I)
            for (int Q = -R / 2; Q < R / 2; ++Q)
            {
                result *pr = &lut[I & (R - 1)][Q & (R - 1)];
                // Simplified metric:
                // Distance to nearest minus distance to second-nearest.
                // Null at edge of decision regions
                // => Suitable for Viterbi with partial metrics.
                uint8_t nearest = 0;
                int32_t cost = R * R * 2, cost2 = R * R * 2;
                for (int s = 0; s < nsymbols; ++s)
                {
                    int32_t d2 = (I - symbols[s].re) * (I - symbols[s].re)
                            + (Q - symbols[s].im) * (Q - symbols[s].im);
                    if (d2 < cost)
                    {
                        cost2 = cost;
                        cost = d2;
                        nearest = s;
                    }
                    else if (d2 < cost2)
                    {
                        cost2 = d2;
                    }
                }
                if (cost > 32767)
                    cost = 32767;
                if (cost2 > 32767)
                    cost2 = 32767;
                pr->ss.cost = cost - cost2;
                pr->ss.symbol = nearest;
                float ph_symbol = atan2f(symbols[pr->ss.symbol].im,
                        symbols[pr->ss.symbol].re);
                float ph_err = atan2f(Q, I) - ph_symbol;
                pr->phase_error = (s32) (ph_err * 65536 / (2 * M_PI)); // Mod 65536
            }
    }

public:
    // Convert soft metric to Hamming distance
    void harden()
    {
        for (int i = 0; i < R; ++i)
            for (int q = 0; q < R; ++q)
            {
                softsymbol *ss = &lut[i][q].ss;
                if (ss->cost < 0)
                    ss->cost = -1;
                if (ss->cost > 0)
                    ss->cost = 1;
            }  // for I,Q
    }

};
// cstln_lut

//static const char *cstln_names[] =
//{ [cstln_lut<256>::BPSK] = "BPSK",
//    [cstln_lut<256>::QPSK] = "QPSK",
//    [cstln_lut<256>::PSK8] = "8PSK",
//    [cstln_lut<256>::APSK16] = "16APSK",
//    [cstln_lut<256>::APSK32] = "32APSK",
//    [cstln_lut<256>::APSK64E] = "64APSKe",
//    [cstln_lut<256>::QAM16] = "16QAM",
//    [cstln_lut<256>::QAM64] = "64QAM",
//    [cstln_lut<256>::QAM256] = "256QAM"
//};

// SAMPLER INTERFACE FOR CSTLN_RECEIVER

template<typename T>
struct sampler_interface
{
    virtual complex<T> interp(const complex<T> *pin, float mu, float phase) = 0;

    virtual void update_freq(float freqw)
    {
        (void) freqw;
    }  // 65536 = 1 Hz

    virtual int readahead()
    {
        return 0;
    }

    virtual ~sampler_interface()
    {
    }
};

// NEAREST-SAMPLE SAMPLER FOR CSTLN_RECEIVER
// Suitable for bandpass-filtered, oversampled signals only

template<typename T>
struct nearest_sampler: sampler_interface<T>
{
    int readahead()
    {
        return 0;
    }

    complex<T> interp(const complex<T> *pin, float mu, float phase)
    {
        (void) mu;
        return pin[0] * trig.expi(-phase);
    }

private:
    trig16 trig;
};
// nearest_sampler

// LINEAR SAMPLER FOR CSTLN_RECEIVER

template<typename T>
struct linear_sampler: sampler_interface<T>
{
    int readahead()
    {
        return 1;
    }

    complex<T> interp(const complex<T> *pin, float mu, float phase)
    {
        // Derotate pin[0] and pin[1]
        complex<T> s0 = pin[0] * trig.expi(-phase);
        complex<T> s1 = pin[1] * trig.expi(-(phase + freqw));
        // Interpolate linearly
        return s0 * (1 - mu) + s1 * mu;
    }

    void update_freq(float _freqw)
    {
        freqw = _freqw;
    }

private:
    trig16 trig;
    float freqw;
};
// linear_sampler

// FIR SAMPLER FOR CSTLN_RECEIVER

template<typename T, typename Tc>
struct fir_sampler: sampler_interface<T>
{
    fir_sampler(int _ncoeffs, Tc *_coeffs, int _subsampling = 1) :
            ncoeffs(_ncoeffs), coeffs(_coeffs), subsampling(_subsampling), shifted_coeffs(
                    new complex<T> [ncoeffs]), update_freq_phase(0)
    {
    }

    int readahead()
    {
        return ncoeffs - 1;
    }

    complex<T> interp(const complex<T> *pin, float mu, float phase)
    {
        // Apply FIR filter with subsampling
        complex<T> acc(0, 0);
        complex<T> *pc = shifted_coeffs + (int) ((1 - mu) * subsampling);
        complex<T> *pcend = shifted_coeffs + ncoeffs;
        if (subsampling == 1)
        {
            // Special case for heavily oversampled signals,
            // where filtering is expensive.
            // gcc-4.9.2 can vectorize this form with NEON on ARM.
            while (pc < pcend)
                acc += (*pc++) * (*pin++);
        }
        else
        {
            // Not vectorized because the coefficients are not
            // guaranteed to be contiguous in memory.
            for (; pc < pcend; pc += subsampling, ++pin)
                acc += (*pc) * (*pin);
        }
        // Derotate
        return trig.expi(-phase) * acc;
    }

    void update_freq(float freqw)
    {
        // Throttling: Update one coeff per 16 processed samples,
        // to keep the overhead of freq tracking below about 10%.
        update_freq_phase -= 128;  // chunk_size of cstln_receiver
        if (update_freq_phase <= 0)
        {
            update_freq_phase = ncoeffs * 16;
            do_update_freq(freqw);
        }
    }

private:
    void do_update_freq(float freqw)
    {
        float f = freqw / subsampling;
        for (int i = 0; i < ncoeffs; ++i)
            shifted_coeffs[i] = trig.expi(-f * (i - ncoeffs / 2)) * coeffs[i];
    }

    trig16 trig;
    int ncoeffs;
    Tc *coeffs;
    int subsampling;
    cf32 *shifted_coeffs;
    int update_freq_phase;
};
// fir_sampler

// CONSTELLATION RECEIVER

// Linear interpolation: good enough for 1.2 samples/symbol,
// but higher oversampling is recommended.

template<typename T>
struct cstln_receiver: runnable
{
    sampler_interface<T> *sampler;
    cstln_lut<256> *cstln;
    unsigned long meas_decimation;      // Measurement rate
    float omega, min_omega, max_omega;  // Samples per symbol
    float freqw, min_freqw, max_freqw;  // Freq offs (65536 = 1 Hz)
    float pll_adjustment;
    bool allow_drift;                   // Follow carrier beyond safe limits
    static const unsigned int chunk_size = 128;
    float kest;

    cstln_receiver(
            scheduler *sch,
            sampler_interface<T> *_sampler,
            pipebuf<complex<T> > &_in,
            pipebuf<softsymbol> &_out,
            pipebuf<float> *_freq_out = NULL,
            pipebuf<float> *_ss_out = NULL,
            pipebuf<float> *_mer_out = NULL,
            pipebuf<cf32> *_cstln_out = NULL) :
        runnable(sch, "Constellation receiver"),
        sampler(_sampler),
        cstln(NULL),
        meas_decimation(1048576),
        pll_adjustment(1.0),
        allow_drift(false),
        kest(0.01),
        in(_in),
        out(_out, chunk_size),
        est_insp(cstln_amp * cstln_amp),
        agc_gain(1),
        mu(0),
        phase(0),
        est_sp(0),
        est_ep(0),
        meas_count(0)
    {
        set_omega(1);
        set_freq(0);
        freq_out = _freq_out ? new pipewriter<float>(*_freq_out) : NULL;
        ss_out = _ss_out ? new pipewriter<float>(*_ss_out) : NULL;
        mer_out = _mer_out ? new pipewriter<float>(*_mer_out) : NULL;
        cstln_out = _cstln_out ? new pipewriter<cf32>(*_cstln_out) : NULL;
        memset(hist, 0, sizeof(hist));
    }

    void set_omega(float _omega, float tol = 10e-6)
    {
        omega = _omega;
        min_omega = omega * (1 - tol);
        max_omega = omega * (1 + tol);
        update_freq_limits();
    }

    void set_freq(float freq)
    {
        freqw = freq * 65536;
        update_freq_limits();
        refresh_freq_tap();
    }

    void set_allow_drift(bool d)
    {
        allow_drift = d;
    }

    void update_freq_limits()
    {
        // Prevent PLL from crossing +-SR/n/2 and locking at +-SR/n.
        int n = 4;
        if (cstln)
        {
            switch (cstln->nsymbols)
            {
            case 2:
                n = 2;
                break;  // BPSK
            case 4:
                n = 4;
                break;  // QPSK
            case 8:
                n = 8;
                break;  // 8PSK
            case 16:
                n = 12;
                break;  // 16APSK
            case 32:
                n = 16;
                break;  // 32APSK
            default:
                n = 4;
                break;
            }
        }
        min_freqw = freqw - 65536 / max_omega / n / 2;
        max_freqw = freqw + 65536 / max_omega / n / 2;
    }

    void run()
    {
        if (!cstln)
        {
            fail("cstln_lut::run", "constellation not set");
            return;
        }

        // Magic constants that work with the qa recordings.
        float freq_alpha = 0.04;
        float freq_beta = 0.0012 / omega * pll_adjustment;
        float gain_mu = 0.02 / (cstln_amp * cstln_amp) * 2;

        unsigned int max_meas = chunk_size / meas_decimation + 1;
        // Large margin on output_size because mu adjustments
        // can lead to more than chunk_size/min_omega symbols.
        while (in.readable() >= chunk_size + sampler->readahead()
                && out.writable() >= chunk_size
                && (!freq_out || freq_out->writable() >= max_meas)
                && (!ss_out || ss_out->writable() >= max_meas)
                && (!mer_out || mer_out->writable() >= max_meas)
                && (!cstln_out || cstln_out->writable() >= max_meas))
        {

            sampler->update_freq(freqw);

            complex<T> *pin = in.rd(), *pin0 = pin, *pend = pin + chunk_size;
            softsymbol *pout = out.wr(), *pout0 = pout;

            // These are scoped outside the loop for SS and MER estimation.
            complex<float> sg(0.0, 0.0); // Symbol before AGC;
            complex<float> s(0.0, 0.0);  // For MER estimation and constellation viewer
            complex<signed char> *cstln_point = NULL;

            while (pin < pend)
            {
                // Here mu is the time of the next symbol counted from 0 at pin.
                if (mu < 1)
                {
                    // Here 0<=mu<1 is the fractional time of the next symbol
                    // between pin and pin+1.
                    sg = sampler->interp(pin, mu, phase);
                    s = sg * agc_gain;

                    // Constellation look-up
                    cstln_lut<256>::result *cr = cstln->lookup(s.re, s.im);
                    *pout = cr->ss;
                    ++pout;

                    // PLL
                    phase += cr->phase_error * freq_alpha;
                    freqw += cr->phase_error * freq_beta;

                    // Modified Mueller and Müller
                    // mu[k]=real((c[k]-c[k-2])*conj(p[k-1])-(p[k]-p[k-2])*conj(c[k-1]))
                    //      =dot(c[k]-c[k-2],p[k-1]) - dot(p[k]-p[k-2],c[k-1])
                    // p = received signals
                    // c = decisions (constellation points)
                    hist[2] = hist[1];
                    hist[1] = hist[0];
                    hist[0].p.re = s.re;
                    hist[0].p.im = s.im;
                    cstln_point = &cstln->symbols[cr->ss.symbol];
                    hist[0].c.re = cstln_point->re;
                    hist[0].c.im = cstln_point->im;
                    float muerr = ((hist[0].p.re - hist[2].p.re) * hist[1].c.re
                            + (hist[0].p.im - hist[2].p.im) * hist[1].c.im)
                            - ((hist[0].c.re - hist[2].c.re) * hist[1].p.re
                                    + (hist[0].c.im - hist[2].c.im)
                                            * hist[1].p.im);
                    float mucorr = muerr * gain_mu;
                    const float max_mucorr = 0.1;
                    // TBD Optimize out statically
                    if (mucorr < -max_mucorr)
                        mucorr = -max_mucorr;
                    if (mucorr > max_mucorr)
                        mucorr = max_mucorr;
                    mu += mucorr;
                    mu += omega;  // Next symbol time;
                } // mu<1

                // Next sample
                ++pin;
                --mu;
                phase += freqw;
            }  // chunk_size

            in.read(pin - pin0);
            out.written(pout - pout0);

            // Normalize phase so that it never exceeds 32 bits.
            // Max freqw is 2^31/65536/chunk_size = 256 Hz
            // (this may happen with leandvb --drift --decim).
            phase = fmodf(phase, 65536);

            if (cstln_point)
            {

                // Output the last interpolated PSK symbol, max once per chunk_size
                if (cstln_out)
                    cstln_out->write(s);

                // AGC
                // For APSK we must do AGC on the symbols, not the whole signal.
                // TODO Use a better estimator at low SNR.
                float insp = sg.re * sg.re + sg.im * sg.im;
                est_insp = insp * kest + est_insp * (1 - kest);
                if (est_insp)
                    agc_gain = cstln_amp / gen_sqrt(est_insp);

                // SS and MER
                complex<float> ev(s.re - cstln_point->re,
                        s.im - cstln_point->im);
                float sig_power, ev_power;
                if (cstln->nsymbols == 2)
                {
                    // Special case for BPSK: Ignore quadrature component of noise.
                    // TBD Projection on I axis assumes BPSK at 45°
                    float sig_real = (cstln_point->re + cstln_point->im)
                            * 0.707;
                    float ev_real = (ev.re + ev.im) * 0.707;
                    sig_power = sig_real * sig_real;
                    ev_power = ev_real * ev_real;
                }
                else
                {
                    sig_power = (int) cstln_point->re * cstln_point->re
                            + (int) cstln_point->im * cstln_point->im;
                    ev_power = ev.re * ev.re + ev.im * ev.im;
                }
                est_sp = sig_power * kest + est_sp * (1 - kest);
                est_ep = ev_power * kest + est_ep * (1 - kest);

            }

            // This is best done periodically ouside the inner loop,
            // but will cause non-deterministic output.

            if (!allow_drift)
            {
                if (freqw < min_freqw || freqw > max_freqw)
                    freqw = (max_freqw + min_freqw) / 2;
            }

            // Output measurements

            refresh_freq_tap();

            meas_count += pin - pin0;
            while (meas_count >= meas_decimation)
            {
                meas_count -= meas_decimation;
                if (freq_out)
                    freq_out->write(freq_tap);
                if (ss_out)
                    ss_out->write(sqrtf(est_insp));
                if (mer_out)
                    mer_out->write(
                            est_ep ? 10 * logf(est_sp / est_ep) / logf(10) : 0);
            }

        }  // Work to do
    }

    float freq_tap;
    void refresh_freq_tap()
    {
        freq_tap = freqw / 65536;
    }
private:
    struct
    {
        complex<float> p;  // Received symbol
        complex<float> c;  // Matched constellation point
    } hist[3];
    pipereader<complex<T> > in;
    pipewriter<softsymbol> out;
    float est_insp, agc_gain;
    float mu;  // PSK time expressed in clock ticks
    float phase;  // 65536=2pi
    // Signal estimation
    float est_sp;  // Estimated RMS signal power
    float est_ep;  // Estimated RMS error vector power
    unsigned long meas_count;
    pipewriter<float> *freq_out, *ss_out, *mer_out;
    pipewriter<cf32> *cstln_out;
};

// FAST QPSK RECEIVER

// Optimized for u8 input, no AGC, uses phase information only.
// Outputs hard symbols.

template<typename T>
struct fast_qpsk_receiver: runnable
{
    typedef u8 hardsymbol;
    unsigned long meas_decimation;      // Measurement rate
    float omega, min_omega, max_omega;  // Samples per symbol
    signed long freqw, min_freqw, max_freqw;  // Freq offs (angle per sample)
    float pll_adjustment;
    bool allow_drift;                   // Follow carrier beyond safe limits
    static const unsigned int chunk_size = 128;

    fast_qpsk_receiver(
            scheduler *sch,
            pipebuf<complex<T> > &_in,
            pipebuf<hardsymbol> &_out,
            pipebuf<float> *_freq_out = NULL,
            pipebuf<complex<T> > *_cstln_out = NULL) :
        runnable(sch, "Fast QPSK receiver"),
        meas_decimation(1048576),
        pll_adjustment(1.0),
        allow_drift(false),
        in(_in),
        out(_out, chunk_size),
        mu(0),
        phase(0),
        meas_count(0)
    {
        set_omega(1);
        set_freq(0);
        freq_out = _freq_out ? new pipewriter<float>(*_freq_out) : NULL;
        cstln_out =
                _cstln_out ? new pipewriter<complex<T> >(*_cstln_out) : NULL;
        memset(hist, 0, sizeof(hist));
        init_lookup_tables();
    }

    void set_omega(float _omega, float tol = 10e-6)
    {
        omega = _omega;
        min_omega = omega * (1 - tol);
        max_omega = omega * (1 + tol);
        update_freq_limits();
    }

    void set_freq(float freq)
    {
        freqw = freq * 65536;
        update_freq_limits();
    }

    void update_freq_limits()
    {
        // Prevent PLL from locking at +-symbolrate/4.
        // TODO The +-SR/8 limit is suitable for QPSK only.
        min_freqw = freqw - 65536 / max_omega / 8;
        max_freqw = freqw + 65536 / max_omega / 8;
    }

    static const int RLUT_BITS = 8;
    static const int RLUT_ANGLES = 1 << RLUT_BITS;

    void run()
    {
        // Magic constants that work with the qa recordings.
        signed long freq_alpha = 0.04 * 65536;
        signed long freq_beta = 0.0012 * 256 * 65536 / omega * pll_adjustment;
        if (!freq_beta)
        {
            fail("fast_qpsk_receiver::run", "Excessive oversampling");
            return;
        }

        float gain_mu = 0.02 / (cstln_amp * cstln_amp) * 2;

        int max_meas = chunk_size / meas_decimation + 1;
        // Largin margin on output_size because mu adjustments
        // can lead to more than chunk_size/min_omega symbols.
        while (in.readable() >= chunk_size + 1
                &&  // +1 for interpolation
                out.writable() >= chunk_size
                && (!freq_out || freq_out->writable() >= max_meas)
                && (!cstln_out || cstln_out->writable() >= max_meas))
        {

            complex<T> *pin = in.rd(), *pin0 = pin, *pend = pin + chunk_size;
            hardsymbol *pout = out.wr(), *pout0 = pout;

            cu8 s;
            u_angle symbol_arg = 0;  // Exported for constellation viewer

            while (pin < pend)
            {
                // Here mu is the time of the next symbol counted from 0 at pin.
                if (mu < 1)
                {
                    // Here 0<=mu<1 is the fractional time of the next symbol
                    // between pin and pin+1.

                    // Derotate and interpolate
#if 0  // Phase only (does not work)
                    // Careful with the float/signed/unsigned casts
                    u_angle a0 = fast_arg(pin[0]) - phase;
                    u_angle a1 = fast_arg(pin[1]) - (phase+freqw);
                    s_angle da = a1 - a0;
                    symbol_arg = a0 + (s_angle)(da*mu);
                    s = arg_to_symbol(symbol_arg);
#elif 1  // Linear by lookup-table. 1.2M on bench3bishs
                    polar *p0 = &lut_polar[pin[0].re][pin[0].im];
                    u_angle a0 = (u_angle) (p0->a - phase) >> (16 - RLUT_BITS);
                    cu8 *p0r = &lut_rect[a0][p0->r >> 1];
                    polar *p1 = &lut_polar[pin[1].re][pin[1].im];
                    u_angle a1 = (u_angle) (p1->a - (phase + freqw))
                            >> (16 - RLUT_BITS);
                    cu8 *p1r = &lut_rect[a1][p1->r >> 1];
                    s.re = (int) (p0r->re + (p1r->re - p0r->re) * mu);
                    s.im = (int) (p0r->im + (p1r->im - p0r->im) * mu);
                    symbol_arg = fast_arg(s);
#else  // Linear floating-point, for reference
                    float a0 = -(int)phase*M_PI/32768;
                    float cosa0=cosf(a0), sina0=sinf(a0);
                    complex<float>
                    p0r(((float)pin[0].re-128)*cosa0 - ((float)pin[0].im-128)*sina0,
                            ((float)pin[0].re-128)*sina0 + ((float)pin[0].im-128)*cosa0);
                    float a1 = -(int)(phase+freqw)*M_PI/32768;
                    float cosa1=cosf(a1), sina1=sinf(a1);
                    complex<float>
                    p1r(((float)pin[1].re-128)*cosa1 - ((float)pin[1].im-128)*sina1,
                            ((float)pin[1].re-128)*sina1 + ((float)pin[1].im-128)*cosa1);
                    s.re = (int)(128 + p0r.re + (p1r.re-p0r.re)*mu);
                    s.im = (int)(128 + p0r.im + (p1r.im-p0r.im)*mu);
                    symbol_arg = fast_arg(s);
#endif

                    int quadrant = symbol_arg >> 14;
                    static unsigned char quadrant_to_symbol[4] =
                    { 0, 2, 3, 1 };
                    *pout = quadrant_to_symbol[quadrant];
                    ++pout;

                    // PLL
                    s_angle phase_error = (s_angle) (symbol_arg & 16383) - 8192;
                    phase += (phase_error * freq_alpha + 32768) >> 16;
                    freqw += (phase_error * freq_beta + 32768 * 256) >> 24;

                    // Modified Mueller and Müller
                    // mu[k]=real((c[k]-c[k-2])*conj(p[k-1])-(p[k]-p[k-2])*conj(c[k-1]))
                    //      =dot(c[k]-c[k-2],p[k-1]) - dot(p[k]-p[k-2],c[k-1])
                    // p = received signals
                    // c = decisions (constellation points)
                    hist[2] = hist[1];
                    hist[1] = hist[0];
#define HIST_FLOAT 0
#if HIST_FLOAT
                    hist[0].p.re = (float)s.re - 128;
                    hist[0].p.im = (float)s.im - 128;

                    cu8 cp = arg_to_symbol((symbol_arg&49152)+8192);
                    hist[0].c.re = (float)cp.re - 128;
                    hist[0].c.im = (float)cp.im - 128;

                    float muerr =
                    ( (hist[0].p.re-hist[2].p.re)*hist[1].c.re +
                            (hist[0].p.im-hist[2].p.im)*hist[1].c.im ) -
                    ( (hist[0].c.re-hist[2].c.re)*hist[1].p.re +
                            (hist[0].c.im-hist[2].c.im)*hist[1].p.im );
#else
                    hist[0].p = s;
                    hist[0].c = arg_to_symbol((symbol_arg & 49152) + 8192);

                    int muerr =
                            ((signed char) (hist[0].p.re - hist[2].p.re)
                                    * ((int) hist[1].c.re - 128)
                                    + (signed char) (hist[0].p.im - hist[2].p.im)
                                            * ((int) hist[1].c.im - 128))
                                    - ((signed char) (hist[0].c.re
                                            - hist[2].c.re)
                                            * ((int) hist[1].p.re - 128)
                                            + (signed char) (hist[0].c.im
                                                    - hist[2].c.im)
                                                    * ((int) hist[1].p.im - 128));
#endif
                    float mucorr = muerr * gain_mu;
                    const float max_mucorr = 0.1;
                    // TBD Optimize out statically
                    if (mucorr < -max_mucorr)
                        mucorr = -max_mucorr;
                    if (mucorr > max_mucorr)
                        mucorr = max_mucorr;
                    mu += mucorr;
                    mu += omega;  // Next symbol time;
                } // mu<1

                // Next sample
                ++pin;
                --mu;
                phase += freqw;
            }  // chunk_size

            in.read(pin - pin0);
            out.written(pout - pout0);

            if (symbol_arg && cstln_out)
                // Output the last interpolated PSK symbol, max once per chunk_size
                cstln_out->write(s);

            // This is best done periodically ouside the inner loop,
            // but will cause non-deterministic output.

            if (!allow_drift)
            {
                if (freqw < min_freqw || freqw > max_freqw)
                    freqw = (max_freqw + min_freqw) / 2;
            }

            // Output measurements

            meas_count += pin - pin0;
            while (meas_count >= meas_decimation)
            {
                meas_count -= meas_decimation;
                if (freq_out)
                    freq_out->write((float) freqw / 65536);
            }

        }  // Work to do
    }

private:

    struct polar
    {
        u_angle a;
        unsigned char r;
    } lut_polar[256][256];
    u_angle fast_arg(const cu8 &c)
    {
        // TBD read cu8 as u16 index, same endianness as in init()
        return lut_polar[c.re][c.im].a;
    }
    cu8 lut_rect[RLUT_ANGLES][256];
    cu8 lut_sincos[65536];
    cu8 arg_to_symbol(u_angle a)
    {
        return lut_sincos[a];
    }
    void init_lookup_tables()
    {
        for (int i = 0; i < 256; ++i)
            for (int q = 0; q < 256; ++q)
            {
                // Don't cast float to unsigned directly
                lut_polar[i][q].a = (s_angle) (atan2f(q - 128, i - 128) * 65536
                        / (2 * M_PI));
                lut_polar[i][q].r = (int) hypotf(i - 128, q - 128);
            }
        for (unsigned long a = 0; a < 65536; ++a)
        {
            float f = 2 * M_PI * a / 65536;
            lut_sincos[a].re = 128 + cstln_amp * cosf(f);
            lut_sincos[a].im = 128 + cstln_amp * sinf(f);
        }
        for (int a = 0; a < RLUT_ANGLES; ++a)
            for (int r = 0; r < 256; ++r)
            {
                lut_rect[a][r].re = (int) (128
                        + r * cos(2 * M_PI * a / RLUT_ANGLES));
                lut_rect[a][r].im = (int) (128
                        + r * sin(2 * M_PI * a / RLUT_ANGLES));
            }
    }

    struct
    {
#if HIST_FLOAT
        complex<float> p;  // Received symbol
        complex<float> c;// Matched constellation point
#else
        cu8 p;  // Received symbol
        cu8 c;  // Matched constellation point
#endif
    } hist[3];
    pipereader<cu8> in;
    pipewriter<hardsymbol> out;
    float mu;  // PSK time expressed in clock ticks. TBD fixed point.
    u_angle phase;
    unsigned long meas_count;
    pipewriter<float> *freq_out, *mer_out;
    pipewriter<cu8> *cstln_out;
};
// fast_qpsk_receiver

// CONSTELLATION TRANSMITTER

// Maps symbols to I/Q points.

template<typename Tout, int Zout>
struct cstln_transmitter: runnable
{
    cstln_lut<256> *cstln;

    cstln_transmitter(scheduler *sch, pipebuf<u8> &_in, pipebuf<complex<Tout> > &_out) :
            runnable(sch, "cstln_transmitter"),
            cstln(0),
            in(_in),
            out(_out)
    {
    }

    void run()
    {
        if (!cstln)
        {
            fail("cstln_transmitter::run", "constellation not set");
            return;
        }
        int count = min(in.readable(), out.writable());
        u8 *pin = in.rd(), *pend = pin + count;
        complex<Tout> *pout = out.wr();
        for (; pin < pend; ++pin, ++pout)
        {
            complex<signed char> *cp = &cstln->symbols[*pin];
            pout->re = Zout + cp->re;
            pout->im = Zout + cp->im;
        }
        in.read(count);
        out.written(count);
    }

private:
    pipereader<u8> in;
    pipewriter<complex<Tout> > out;
};
// cstln_transmitter

// FREQUENCY SHIFTER

// Resolution is sample_freq/65536.

template<typename T>
struct rotator: runnable
{
    rotator(scheduler *sch, pipebuf<complex<T> > &_in, pipebuf<complex<T> > &_out, float freq) :
            runnable(sch, "rotator"),
            in(_in),
            out(_out),
            index(0)
    {
        int ifreq = freq * 65536;
        if (sch->debug)
            fprintf(stderr, "Rotate: req=%f real=%f\n", freq, ifreq / 65536.0);
        for (int i = 0; i < 65536; ++i)
        {
            lut_cos[i] = cosf(2 * M_PI * i * ifreq / 65536);
            lut_sin[i] = sinf(2 * M_PI * i * ifreq / 65536);
        }
    }

    void run()
    {
        unsigned long count = min(in.readable(), out.writable());
        complex<T> *pin = in.rd(), *pend = pin + count;
        complex<T> *pout = out.wr();
        for (; pin < pend; ++pin, ++pout, ++index)
        {
            float c = lut_cos[index];
            float s = lut_sin[index];
            pout->re = pin->re * c - pin->im * s;
            pout->im = pin->re * s + pin->im * c;
        }
        in.read(count);
        out.written(count);
    }

private:
    pipereader<complex<T> > in;
    pipewriter<complex<T> > out;
    float lut_cos[65536];
    float lut_sin[65536];
    unsigned short index;  // Current phase
};
// rotator

// SPECTRUM-BASED CNR ESTIMATOR

// Assumes that the spectrum is as follows:
//
//  ---|--noise---|-roll-off-|---carrier+noise----|-roll-off-|---noise--|---
//     |  (bw/2)  |   (bw)   |       (bw/2)       |   (bw)   |  (bw/2)  |
//
// Maximum roll-off 0.5

template<typename T>
struct cnr_fft: runnable
{
    cnr_fft(scheduler *sch, pipebuf<complex<T> > &_in, pipebuf<float> &_out, float _bandwidth, int nfft = 4096) :
            runnable(sch, "cnr_fft"),
            bandwidth(_bandwidth),
            freq_tap(NULL),
            tap_multiplier(1),
            decimation(1048576),
            kavg(0.1),
            in(_in),
            out(_out),
            fft(nfft),
            avgpower(NULL),
            phase(0)
    {
        if (bandwidth > 0.25) {
            fail("cnr_fft::cnr_fft", "CNR estimator requires Fsampling > 4x Fsignal");
        }
        m_data.allocate(fft.n);
        m_power.allocate(fft.n);
    }

    float bandwidth;
    float *freq_tap, tap_multiplier;
    int decimation;
    float kavg;
    IncrementalArray<complex<T> > m_data;
    IncrementalArray<T> m_power;

    void run()
    {
        while (in.readable() >= fft.n && out.writable() >= 1)
        {
            phase += fft.n;
            if (phase >= decimation)
            {
                phase -= decimation;
                do_cnr();
            }
            in.read(fft.n);
        }
    }

private:

    void do_cnr()
    {
        float center_freq = freq_tap ? *freq_tap * tap_multiplier : 0;
        int icf = floor(center_freq * fft.n + 0.5);
        //complex<T> data[fft.n];
        complex<T> *data = m_data.m_array;
        memcpy(data, in.rd(), fft.n * sizeof(data[0]));
        fft.inplace(data, true);
        //T power[fft.n];
        T *power = m_power.m_array;
        for (unsigned int i = 0; i < fft.n; ++i)
            power[i] = data[i].re * data[i].re + data[i].im * data[i].im;
        if (!avgpower)
        {
            // Initialize with first spectrum
            avgpower = new T[fft.n];
            memcpy(avgpower, power, fft.n * sizeof(avgpower[0]));
        }
        // Accumulate and low-pass filter
        for (unsigned int i = 0; i < fft.n; ++i)
            avgpower[i] = avgpower[i] * (1 - kavg) + power[i] * kavg;

        int bw__slots = (bandwidth / 4) * fft.n;
        if (!bw__slots)
            return;
        // Measure carrier+noise in center band
        float c2plusn2 = avg__slots(icf - bw__slots, icf + bw__slots);
        // Measure noise left and right of roll-off zones
        float n2 = (avg__slots(icf - bw__slots * 4, icf - bw__slots * 3)
                + avg__slots(icf + bw__slots * 3, icf + bw__slots * 4)) / 2;
        float c2 = c2plusn2 - n2;
        float cnr = (c2 > 0 && n2 > 0) ? 10 * logf(c2 / n2) / logf(10) : -50;
        out.write(cnr);
    }

    float avg__slots(int i0, int i1)
    {  // i0 <= i1
        T s = 0;
        for (int i = i0; i <= i1; ++i)
            s += avgpower[i & (fft.n - 1)];
        return s / (i1 - i0 + 1);
    }

    pipereader<complex<T> > in;
    pipewriter<float> out;
    cfft_engine<T> fft;
    T *avgpower;
    int phase;
};
// cnr_fft

template<typename T>
struct spectrum: runnable
{
    static const int nfft = 1024;
    spectrum(scheduler *sch, pipebuf<complex<T> > &_in, pipebuf<float[nfft]> &_out) :
            runnable(sch, "spectrum"),
            decimation(1048576),
            kavg(0.1),
            in(_in),
            out(_out),
            fft(nfft),
            avgpower(NULL),
            phase(0)
    {
    }

    int decimation;
    float kavg;

    void run()
    {
        while (in.readable() >= fft.n && out.writable() >= 1)
        {
            phase += fft.n;
            if (phase >= decimation)
            {
                phase -= decimation;
                do_spectrum();
            }
            in.read(fft.n);
        }
    }

private:

    void do_spectrum()
    {
        complex<T> data[fft.n];
        memcpy(data, in.rd(), fft.n * sizeof(data[0]));
        fft.inplace(data, true);
        float power[nfft];
        for (int i = 0; i < fft.n; ++i)
            power[i] = (float) data[i].re * data[i].re
                    + (float) data[i].im * data[i].im;
        if (!avgpower)
        {
            // Initialize with first spectrum
            avgpower = new float[fft.n];
            memcpy(avgpower, power, fft.n * sizeof(avgpower[0]));
        }
        // Accumulate and low-pass filter
        for (int i = 0; i < fft.n; ++i)
            avgpower[i] = avgpower[i] * (1 - kavg) + power[i] * kavg;

        // Reuse power[]
        for (int i = 0; i < fft.n / 2; ++i)
        {
            power[i] = 10 * log10f(avgpower[nfft / 2 + i]);
            power[nfft / 2 + i] = 10 * log10f(avgpower[i]);
        }
        memcpy(out.wr(), power, sizeof(power[0]) * nfft);
        out.written(1);
    }

    pipereader<complex<T> > in;
    pipewriter<float[nfft]> out;
    cfft_engine<T> fft;
    T *avgpower;
    int phase;
};
// spectrum

}// namespace

#endif  // LEANSDR_SDR_H