sdrangel/libfreedv/freedv_vhf_framing.h

/*---------------------------------------------------------------------------*\

  FILE........: freedv_vhf_framing.h
  AUTHOR......: Brady O'Brien
  DATE CREATED: 11 February 2016

  Framer and deframer for VHF FreeDV modes 'A' and 'B'
  Currently designed for-
  * 40ms ota modem frames
  * 40ms Codec2 1300 frames
  * 52 bits of Codec2 per frame
  * 16 bits of unique word per frame
  * 28 'spare' bits per frame
  *  - 4 spare bits at front and end of frame (8 total) for padding
  *  - 20 'protocol' bits, either for higher layers of 'protocol' or
  *  - 18 'protocol' bits and 2 vericode sidechannel bits
\*---------------------------------------------------------------------------*/

/*
  Copyright (C) 2016 David Rowe

  All rights reserved.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License version 2.1, as
  published by the Free Software Foundation.  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 for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with this program; if not, see <http://www.gnu.org/licenses/>.
*/

#ifndef _FREEDV_VHF_FRAMING_H
#define _FREEDV_VHF_FRAMING_H

#include <cstddef>
#include "freedv_data_channel.h"

/* Standard frame type */
#define FREEDV_VHF_FRAME_A 1    /* 2400A/B Frame */
#define FREEDV_HF_FRAME_B 2     /* 800XA Frame */
#define FREEDV_VHF_FRAME_AT 3   /* 4800T Frame */

namespace FreeDV
{

struct freedv_vhf_deframer {
    int ftype;          /* Type of frame to be looking for */
    int state;          /* State of deframer */
    uint8_t * bits;     /* Bits currently being decanted */
    uint8_t * invbits;  /* Inversion of bits currently being decanted, for FMFSK */

    int bitptr;         /* Pointer into circular bit buffer */
    int miss_cnt;       /* How many UWs have been missed */
    int last_uw;        /* How many bits since the last UW? */
    int frame_size;     /* How big is a frame? */
    int uw_size;        /* How big is the UW */
    int on_inv_bits;    /* Are we using the inverted bits? */
    int sym_size;       /* How many bits in a modem symbol */

    float ber_est;      /* Bit error rate estimate */
    int total_uw_bits;  /* Total RX-ed bits of UW */
    int total_uw_err;   /* Total errors in UW bits */

    struct freedv_data_channel *fdc;
};

/* Init and allocate memory for a freedv-vhf framer/deframer */
struct freedv_vhf_deframer * fvhff_create_deframer(uint8_t frame_type,int enable_bit_flip);

/* Get size of various frame parameters */
/* Frame size in bits */
int fvhff_get_frame_size(struct freedv_vhf_deframer * def);
/* Codec2 size in bytes */
int fvhff_get_codec2_size(struct freedv_vhf_deframer * def);
/* Protocol bits in bits */
int fvhff_get_proto_size(struct freedv_vhf_deframer * def);
/* Varicode bits in bits */
int fvhff_get_varicode_size(struct freedv_vhf_deframer * def);

/* Free the memory used by a freedv-vhf framer/deframer */
void fvhff_destroy_deframer(struct freedv_vhf_deframer * def);

/* Place codec and other bits into a frame */
void fvhff_frame_bits(int frame_type,uint8_t bits_out[],uint8_t codec2_in[],uint8_t proto_in[],uint8_t vc_in[]);
void fvhff_frame_data_bits(struct freedv_vhf_deframer * def, int frame_type,uint8_t bits_out[]);

/* Find and extract frames from a stream of bits */
int fvhff_deframe_bits(struct freedv_vhf_deframer * def,uint8_t codec2_out[],uint8_t proto_out[],uint8_t vc_out[],uint8_t bits_in[]);

/* Is the de-framer synchronized? */
int fvhff_synchronized(struct freedv_vhf_deframer * def);

/* Search for a complete UW in a buffer of bits */
std::size_t fvhff_search_uw(const uint8_t bits[],size_t nbits,
  const uint8_t uw[],    std::size_t uw_len,
  std::size_t * delta_out,    std::size_t bits_per_sym);

} // FreeDV

#endif //_FREEDV_VHF_FRAMING_H