PeerStreamer

/*

 * G.729 decoder

 * Copyright (c) 2008 Vladimir Voroshilov

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2.1 of the License, or (at your option) any later version.

 *

 * FFmpeg 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include <stdlib.h>

#include <inttypes.h>

#include <limits.h>

#include <stdio.h>

#include <string.h>

#include <math.h>

#include <assert.h>

#include "avcodec.h"

#include "libavutil/avutil.h"

#include "get_bits.h"

#include "g729.h"

#include "lsp.h"

#include "celp_math.h"

#include "acelp_filters.h"

#include "acelp_pitch_delay.h"

#include "acelp_vectors.h"

#include "g729data.h"

/**

 * minimum quantized LSF value (3.2.4)

 * 0.005 in Q13

 */

#define LSFQ_MIN                   40

/**

 * maximum quantized LSF value (3.2.4)

 * 3.135 in Q13

 */

#define LSFQ_MAX                   25681

/**

 * minimum LSF distance (3.2.4)

 * 0.0391 in Q13

 */

#define LSFQ_DIFF_MIN              321

/**

 * minimum gain pitch value (3.8, Equation 47)

 * 0.2 in (1.14)

 */

#define SHARP_MIN                  3277

/**

 * maximum gain pitch value (3.8, Equation 47)

 * (EE) This does not comply with the specification.

 * Specification says about 0.8, which should be

 * 13107 in (1.14), but reference C code uses

 * 13017 (equals to 0.7945) instead of it.

 */

#define SHARP_MAX                  13017

typedef struct {

    uint8_t ac_index_bits[2];   ///< adaptive codebook index for second subframe (size in bits)

    uint8_t parity_bit;         ///< parity bit for pitch delay

    uint8_t gc_1st_index_bits;  ///< gain codebook (first stage) index (size in bits)

    uint8_t gc_2nd_index_bits;  ///< gain codebook (second stage) index (size in bits)

    uint8_t fc_signs_bits;      ///< number of pulses in fixed-codebook vector

    uint8_t fc_indexes_bits;    ///< size (in bits) of fixed-codebook index entry

} G729FormatDescription;

typedef struct {

    int pitch_delay_int_prev;   ///< integer part of previous subframe's pitch delay (4.1.3)

    /// (2.13) LSP quantizer outputs

    int16_t  past_quantizer_output_buf[MA_NP + 1][10];

    int16_t* past_quantizer_outputs[MA_NP + 1];

    int16_t lsfq[10];           ///< (2.13) quantized LSF coefficients from previous frame

    int16_t lsp_buf[2][10];     ///< (0.15) LSP coefficients (previous and current frames) (3.2.5)

    int16_t *lsp[2];            ///< pointers to lsp_buf

}  G729Context;

static const G729FormatDescription format_g729_8k = {

    .ac_index_bits     = {8,5},

    .parity_bit        = 1,

    .gc_1st_index_bits = GC_1ST_IDX_BITS_8K,

    .gc_2nd_index_bits = GC_2ND_IDX_BITS_8K,

    .fc_signs_bits     = 4,

    .fc_indexes_bits   = 13,

};

static const G729FormatDescription format_g729d_6k4 = {

    .ac_index_bits     = {8,4},

    .parity_bit        = 0,

    .gc_1st_index_bits = GC_1ST_IDX_BITS_6K4,

    .gc_2nd_index_bits = GC_2ND_IDX_BITS_6K4,

    .fc_signs_bits     = 2,

    .fc_indexes_bits   = 9,

};

/**

 * \brief pseudo random number generator

 */

static inline uint16_t g729_prng(uint16_t value)

{

    return 31821 * value + 13849;

}

/**

 * Get parity bit of bit 2..7

 */

static inline int get_parity(uint8_t value)

{

   return (0x6996966996696996ULL >> (value >> 2)) & 1;

}

static void lsf_decode(int16_t* lsfq, int16_t* past_quantizer_outputs[MA_NP + 1],

                       int16_t ma_predictor,

                       int16_t vq_1st, int16_t vq_2nd_low, int16_t vq_2nd_high)

{

    int i,j;

    static const uint8_t min_distance[2]={10, 5}; //(2.13)

    int16_t* quantizer_output = past_quantizer_outputs[MA_NP];

    for (i = 0; i < 5; i++) {

        quantizer_output[i]     = cb_lsp_1st[vq_1st][i    ] + cb_lsp_2nd[vq_2nd_low ][i    ];

        quantizer_output[i + 5] = cb_lsp_1st[vq_1st][i + 5] + cb_lsp_2nd[vq_2nd_high][i + 5];

    }

    for (j = 0; j < 2; j++) {

        for (i = 1; i < 10; i++) {

            int diff = (quantizer_output[i - 1] - quantizer_output[i] + min_distance[j]) >> 1;

            if (diff > 0) {

                quantizer_output[i - 1] -= diff;

                quantizer_output[i    ] += diff;

            }

        }

    }

    for (i = 0; i < 10; i++) {

        int sum = quantizer_output[i] * cb_ma_predictor_sum[ma_predictor][i];

        for (j = 0; j < MA_NP; j++)

            sum += past_quantizer_outputs[j][i] * cb_ma_predictor[ma_predictor][j][i];

        lsfq[i] = sum >> 15;

    }

    /* Rotate past_quantizer_outputs. */

    memmove(past_quantizer_outputs + 1, past_quantizer_outputs, MA_NP * sizeof(int16_t*));

    past_quantizer_outputs[0] = quantizer_output;

    ff_acelp_reorder_lsf(lsfq, LSFQ_DIFF_MIN, LSFQ_MIN, LSFQ_MAX, 10);

}

static av_cold int decoder_init(AVCodecContext * avctx)

{

    G729Context* ctx = avctx->priv_data;

    int i,k;

    if (avctx->channels != 1) {

        av_log(avctx, AV_LOG_ERROR, "Only mono sound is supported (requested channels: %d).\n", avctx->channels);

        return AVERROR(EINVAL);

    }

    /* Both 8kbit/s and 6.4kbit/s modes uses two subframes per frame. */

    avctx->frame_size = SUBFRAME_SIZE << 1;

    for (k = 0; k < MA_NP + 1; k++) {

        ctx->past_quantizer_outputs[k] = ctx->past_quantizer_output_buf[k];

        for (i = 1; i < 11; i++)

            ctx->past_quantizer_outputs[k][i - 1] = (18717 * i) >> 3;

    }

    ctx->lsp[0] = ctx->lsp_buf[0];

    ctx->lsp[1] = ctx->lsp_buf[1];

    memcpy(ctx->lsp[0], lsp_init, 10 * sizeof(int16_t));

    return 0;

}

static int decode_frame(AVCodecContext *avctx, void *data, int *data_size,

                        AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    int buf_size       = avpkt->size;

    int16_t *out_frame = data;

    GetBitContext gb;

    G729FormatDescription format;

    int frame_erasure = 0;    ///< frame erasure detected during decoding

    int bad_pitch = 0;        ///< parity check failed

    int i;

    G729Context *ctx = avctx->priv_data;

    int16_t lp[2][11];           // (3.12)

    uint8_t ma_predictor;     ///< switched MA predictor of LSP quantizer

    uint8_t quantizer_1st;    ///< first stage vector of quantizer

    uint8_t quantizer_2nd_lo; ///< second stage lower vector of quantizer (size in bits)

    uint8_t quantizer_2nd_hi; ///< second stage higher vector of quantizer (size in bits)

    int pitch_delay_int;         // pitch delay, integer part

    int pitch_delay_3x;          // pitch delay, multiplied by 3

    if (*data_size < SUBFRAME_SIZE << 2) {

        av_log(avctx, AV_LOG_ERROR, "Error processing packet: output buffer too small\n");

        return AVERROR(EIO);

    }

    if (buf_size == 10) {

        format = format_g729_8k;

        av_log(avctx, AV_LOG_DEBUG, "Packet type: %s\n", "G.729 @ 8kbit/s");

    } else if (buf_size == 8) {

        format = format_g729d_6k4;

        av_log(avctx, AV_LOG_DEBUG, "Packet type: %s\n", "G.729D @ 6.4kbit/s");

    } else {

        av_log(avctx, AV_LOG_ERROR, "Packet size %d is unknown.\n", buf_size);

        return AVERROR_INVALIDDATA;

    }

    for (i=0; i < buf_size; i++)

        frame_erasure |= buf[i];

    frame_erasure = !frame_erasure;

    init_get_bits(&gb, buf, buf_size);

    ma_predictor     = get_bits(&gb, 1);

    quantizer_1st    = get_bits(&gb, VQ_1ST_BITS);

    quantizer_2nd_lo = get_bits(&gb, VQ_2ND_BITS);

    quantizer_2nd_hi = get_bits(&gb, VQ_2ND_BITS);

    lsf_decode(ctx->lsfq, ctx->past_quantizer_outputs,

               ma_predictor,

               quantizer_1st, quantizer_2nd_lo, quantizer_2nd_hi);

    ff_acelp_lsf2lsp(ctx->lsp[1], ctx->lsfq, 10);

    ff_acelp_lp_decode(&lp[0][0], &lp[1][0], ctx->lsp[1], ctx->lsp[0], 10);

    FFSWAP(int16_t*, ctx->lsp[1], ctx->lsp[0]);

    for (i = 0; i < 2; i++) {

        uint8_t ac_index;      ///< adaptive codebook index

        uint8_t pulses_signs;  ///< fixed-codebook vector pulse signs

        int fc_indexes;        ///< fixed-codebook indexes

        uint8_t gc_1st_index;  ///< gain codebook (first stage) index

        uint8_t gc_2nd_index;  ///< gain codebook (second stage) index

        ac_index      = get_bits(&gb, format.ac_index_bits[i]);

        if(!i && format.parity_bit)

            bad_pitch = get_parity(ac_index) == get_bits1(&gb);

        fc_indexes    = get_bits(&gb, format.fc_indexes_bits);

        pulses_signs  = get_bits(&gb, format.fc_signs_bits);

        gc_1st_index  = get_bits(&gb, format.gc_1st_index_bits);

        gc_2nd_index  = get_bits(&gb, format.gc_2nd_index_bits);

        if(!i) {

            if (bad_pitch)

                pitch_delay_3x   = 3 * ctx->pitch_delay_int_prev;

            else

                pitch_delay_3x = ff_acelp_decode_8bit_to_1st_delay3(ac_index);

        } else {

            int pitch_delay_min = av_clip(ctx->pitch_delay_int_prev - 5,

                                          PITCH_DELAY_MIN, PITCH_DELAY_MAX - 9);

            if(packet_type == FORMAT_G729D_6K4)

                pitch_delay_3x = ff_acelp_decode_4bit_to_2nd_delay3(ac_index, pitch_delay_min);

            else

                pitch_delay_3x = ff_acelp_decode_5_6_bit_to_2nd_delay3(ac_index, pitch_delay_min);

        }

        /* Round pitch delay to nearest (used everywhere except ff_acelp_interpolate). */

        pitch_delay_int  = (pitch_delay_3x + 1) / 3;

        ff_acelp_weighted_vector_sum(fc + pitch_delay_int,

                                     fc + pitch_delay_int,

                                     fc, 1 << 14,

                                     av_clip(ctx->gain_pitch, SHARP_MIN, SHARP_MAX),

                                     0, 14,

                                     SUBFRAME_SIZE - pitch_delay_int);

        if (frame_erasure) {

            ctx->gain_pitch = (29491 * ctx->gain_pitch) >> 15; // 0.90 (0.15)

            ctx->gain_code  = ( 2007 * ctx->gain_code ) >> 11; // 0.98 (0.11)

            gain_corr_factor = 0;

        } else {

            ctx->gain_pitch  = cb_gain_1st_8k[gc_1st_index][0] +

                               cb_gain_2nd_8k[gc_2nd_index][0];

            gain_corr_factor = cb_gain_1st_8k[gc_1st_index][1] +

                               cb_gain_2nd_8k[gc_2nd_index][1];

        ff_acelp_weighted_vector_sum(ctx->exc + i * SUBFRAME_SIZE,

                                     ctx->exc + i * SUBFRAME_SIZE, fc,

                                     (!voicing && frame_erasure) ? 0 : ctx->gain_pitch,

                                     ( voicing && frame_erasure) ? 0 : ctx->gain_code,

                                     1 << 13, 14, SUBFRAME_SIZE);

            ctx->pitch_delay_int_prev = pitch_delay_int;

    }

    *data_size = SUBFRAME_SIZE << 2;

    return buf_size;

}

AVCodec g729_decoder =

{

    "g729",

    CODEC_TYPE_AUDIO,

    CODEC_ID_G729,

    sizeof(G729Context),

    decoder_init,

    NULL,

    NULL,

    decode_frame,

    .long_name = NULL_IF_CONFIG_SMALL("G.729"),

};