mpegaudiodec.c

        /* normalize to 23 frac bits */
        v = tab[i] << (23 - FRAC_BITS);
        fwrite(&v, 1, sizeof(int32_t), f);
    }
}
#endif


/* main layer3 decoding function */
static int mp_decode_layer3(MPADecodeContext *s)
{
    int nb_granules, main_data_begin, private_bits;
    int gr, ch, blocksplit_flag, i, j, k, n, bits_pos;
    GranuleDef granules[2][2], *g;
    int16_t exponents[576];

    /* read side info */
    if (s->lsf) {
        main_data_begin = get_bits(&s->gb, 8);
        private_bits = get_bits(&s->gb, s->nb_channels);
        nb_granules = 1;
    } else {
        main_data_begin = get_bits(&s->gb, 9);
        if (s->nb_channels == 2)
            private_bits = get_bits(&s->gb, 3);
        else
            private_bits = get_bits(&s->gb, 5);
        nb_granules = 2;
        for(ch=0;ch<s->nb_channels;ch++) {
            granules[ch][0].scfsi = 0; /* all scale factors are transmitted */
            granules[ch][1].scfsi = get_bits(&s->gb, 4);
        }
    }

    for(gr=0;gr<nb_granules;gr++) {
        for(ch=0;ch<s->nb_channels;ch++) {
            dprintf(s->avctx, "gr=%d ch=%d: side_info\n", gr, ch);
            g = &granules[ch][gr];
            g->part2_3_length = get_bits(&s->gb, 12);
            g->big_values = get_bits(&s->gb, 9);
            if(g->big_values > 288){
                av_log(s->avctx, AV_LOG_ERROR, "big_values too big\n");
                return -1;
            }

            g->global_gain = get_bits(&s->gb, 8);
            /* if MS stereo only is selected, we precompute the
               1/sqrt(2) renormalization factor */
            if ((s->mode_ext & (MODE_EXT_MS_STEREO | MODE_EXT_I_STEREO)) ==
                MODE_EXT_MS_STEREO)
                g->global_gain -= 2;
            if (s->lsf)
                g->scalefac_compress = get_bits(&s->gb, 9);
            else
                g->scalefac_compress = get_bits(&s->gb, 4);
            blocksplit_flag = get_bits1(&s->gb);
            if (blocksplit_flag) {
                g->block_type = get_bits(&s->gb, 2);
                if (g->block_type == 0){
                    av_log(NULL, AV_LOG_ERROR, "invalid block type\n");
                    return -1;
                }
                g->switch_point = get_bits1(&s->gb);
                for(i=0;i<2;i++)
                    g->table_select[i] = get_bits(&s->gb, 5);
                for(i=0;i<3;i++)
                    g->subblock_gain[i] = get_bits(&s->gb, 3);
                ff_init_short_region(s, g);
            } else {
                int region_address1, region_address2;
                g->block_type = 0;
                g->switch_point = 0;
                for(i=0;i<3;i++)
                    g->table_select[i] = get_bits(&s->gb, 5);
                /* compute huffman coded region sizes */
                region_address1 = get_bits(&s->gb, 4);
                region_address2 = get_bits(&s->gb, 3);
                dprintf(s->avctx, "region1=%d region2=%d\n",
                        region_address1, region_address2);
                ff_init_long_region(s, g, region_address1, region_address2);
            }
            ff_region_offset2size(g);
            ff_compute_band_indexes(s, g);

            g->preflag = 0;
            if (!s->lsf)
                g->preflag = get_bits1(&s->gb);
            g->scalefac_scale = get_bits1(&s->gb);
            g->count1table_select = get_bits1(&s->gb);
            dprintf(s->avctx, "block_type=%d switch_point=%d\n",
                    g->block_type, g->switch_point);
        }
    }

  if (!s->adu_mode) {
    const uint8_t *ptr = s->gb.buffer + (get_bits_count(&s->gb)>>3);
    assert((get_bits_count(&s->gb) & 7) == 0);
    /* now we get bits from the main_data_begin offset */
    dprintf(s->avctx, "seekback: %d\n", main_data_begin);
//av_log(NULL, AV_LOG_ERROR, "backstep:%d, lastbuf:%d\n", main_data_begin, s->last_buf_size);

    memcpy(s->last_buf + s->last_buf_size, ptr, EXTRABYTES);
    s->in_gb= s->gb;
        init_get_bits(&s->gb, s->last_buf, s->last_buf_size*8);
        skip_bits_long(&s->gb, 8*(s->last_buf_size - main_data_begin));
  }

    for(gr=0;gr<nb_granules;gr++) {
        for(ch=0;ch<s->nb_channels;ch++) {
            g = &granules[ch][gr];
            if(get_bits_count(&s->gb)<0){
                av_log(NULL, AV_LOG_ERROR, "mdb:%d, lastbuf:%d skipping granule %d\n",
                                            main_data_begin, s->last_buf_size, gr);
                skip_bits_long(&s->gb, g->part2_3_length);
                memset(g->sb_hybrid, 0, sizeof(g->sb_hybrid));
                if(get_bits_count(&s->gb) >= s->gb.size_in_bits && s->in_gb.buffer){
                    skip_bits_long(&s->in_gb, get_bits_count(&s->gb) - s->gb.size_in_bits);
                    s->gb= s->in_gb;
                    s->in_gb.buffer=NULL;
                }
                continue;
            }

            bits_pos = get_bits_count(&s->gb);

            if (!s->lsf) {
                uint8_t *sc;
                int slen, slen1, slen2;

                /* MPEG1 scale factors */
                slen1 = slen_table[0][g->scalefac_compress];
                slen2 = slen_table[1][g->scalefac_compress];
                dprintf(s->avctx, "slen1=%d slen2=%d\n", slen1, slen2);
                if (g->block_type == 2) {
                    n = g->switch_point ? 17 : 18;
                    j = 0;
                    if(slen1){
                        for(i=0;i<n;i++)
                            g->scale_factors[j++] = get_bits(&s->gb, slen1);
                    }else{
                        for(i=0;i<n;i++)
                            g->scale_factors[j++] = 0;
                    }
                    if(slen2){
                        for(i=0;i<18;i++)
                            g->scale_factors[j++] = get_bits(&s->gb, slen2);
                        for(i=0;i<3;i++)
                            g->scale_factors[j++] = 0;
                    }else{
                        for(i=0;i<21;i++)
                            g->scale_factors[j++] = 0;
                    }
                } else {
                    sc = granules[ch][0].scale_factors;
                    j = 0;
                    for(k=0;k<4;k++) {
                        n = (k == 0 ? 6 : 5);
                        if ((g->scfsi & (0x8 >> k)) == 0) {
                            slen = (k < 2) ? slen1 : slen2;
                            if(slen){
                                for(i=0;i<n;i++)
                                    g->scale_factors[j++] = get_bits(&s->gb, slen);
                            }else{
                                for(i=0;i<n;i++)
                                    g->scale_factors[j++] = 0;
                            }
                        } else {
                            /* simply copy from last granule */
                            for(i=0;i<n;i++) {
                                g->scale_factors[j] = sc[j];
                                j++;
                            }
                        }
                    }
                    g->scale_factors[j++] = 0;
                }
#if defined(DEBUG)
                {
                    dprintf(s->avctx, "scfsi=%x gr=%d ch=%d scale_factors:\n",
                           g->scfsi, gr, ch);
                    for(i=0;i<j;i++)
                        dprintf(s->avctx, " %d", g->scale_factors[i]);
                    dprintf(s->avctx, "\n");
                }
#endif
            } else {
                int tindex, tindex2, slen[4], sl, sf;

                /* LSF scale factors */
                if (g->block_type == 2) {
                    tindex = g->switch_point ? 2 : 1;
                } else {
                    tindex = 0;
                }
                sf = g->scalefac_compress;
                if ((s->mode_ext & MODE_EXT_I_STEREO) && ch == 1) {
                    /* intensity stereo case */
                    sf >>= 1;
                    if (sf < 180) {
                        lsf_sf_expand(slen, sf, 6, 6, 0);
                        tindex2 = 3;
                    } else if (sf < 244) {
                        lsf_sf_expand(slen, sf - 180, 4, 4, 0);
                        tindex2 = 4;
                    } else {
                        lsf_sf_expand(slen, sf - 244, 3, 0, 0);
                        tindex2 = 5;
                    }
                } else {
                    /* normal case */
                    if (sf < 400) {
                        lsf_sf_expand(slen, sf, 5, 4, 4);
                        tindex2 = 0;
                    } else if (sf < 500) {
                        lsf_sf_expand(slen, sf - 400, 5, 4, 0);
                        tindex2 = 1;
                    } else {
                        lsf_sf_expand(slen, sf - 500, 3, 0, 0);
                        tindex2 = 2;
                        g->preflag = 1;
                    }
                }

                j = 0;
                for(k=0;k<4;k++) {
                    n = lsf_nsf_table[tindex2][tindex][k];
                    sl = slen[k];
                    if(sl){
                        for(i=0;i<n;i++)
                            g->scale_factors[j++] = get_bits(&s->gb, sl);
                    }else{
                        for(i=0;i<n;i++)
                            g->scale_factors[j++] = 0;
                    }
                }
                /* XXX: should compute exact size */
                for(;j<40;j++)
                    g->scale_factors[j] = 0;
#if defined(DEBUG)
                {
                    dprintf(s->avctx, "gr=%d ch=%d scale_factors:\n",
                           gr, ch);
                    for(i=0;i<40;i++)
                        dprintf(s->avctx, " %d", g->scale_factors[i]);
                    dprintf(s->avctx, "\n");
                }
#endif
            }

            exponents_from_scale_factors(s, g, exponents);

            /* read Huffman coded residue */
            huffman_decode(s, g, exponents, bits_pos + g->part2_3_length);
#if defined(DEBUG)
            sample_dump(0, g->sb_hybrid, 576);
#endif
        } /* ch */

        if (s->nb_channels == 2)
            compute_stereo(s, &granules[0][gr], &granules[1][gr]);

        for(ch=0;ch<s->nb_channels;ch++) {
            g = &granules[ch][gr];

            reorder_block(s, g);
#if defined(DEBUG)
            sample_dump(0, g->sb_hybrid, 576);
#endif
            s->compute_antialias(s, g);
#if defined(DEBUG)
            sample_dump(1, g->sb_hybrid, 576);
#endif
            compute_imdct(s, g, &s->sb_samples[ch][18 * gr][0], s->mdct_buf[ch]);
#if defined(DEBUG)
            sample_dump(2, &s->sb_samples[ch][18 * gr][0], 576);
#endif
        }
    } /* gr */
    if(get_bits_count(&s->gb)<0)
        skip_bits_long(&s->gb, -get_bits_count(&s->gb));
    return nb_granules * 18;
}

static int mp_decode_frame(MPADecodeContext *s,
                           OUT_INT *samples, const uint8_t *buf, int buf_size)
{
    int i, nb_frames, ch;
    OUT_INT *samples_ptr;

    init_get_bits(&s->gb, buf + HEADER_SIZE, (buf_size - HEADER_SIZE)*8);

    /* skip error protection field */
    if (s->error_protection)
        skip_bits(&s->gb, 16);

    dprintf(s->avctx, "frame %d:\n", s->frame_count);
    switch(s->layer) {
    case 1:
        s->avctx->frame_size = 384;
        nb_frames = mp_decode_layer1(s);
        break;
    case 2:
        s->avctx->frame_size = 1152;
        nb_frames = mp_decode_layer2(s);
        break;
    case 3:
        s->avctx->frame_size = s->lsf ? 576 : 1152;
    default:
        nb_frames = mp_decode_layer3(s);

        s->last_buf_size=0;
        if(s->in_gb.buffer){
            align_get_bits(&s->gb);
            i= (s->gb.size_in_bits - get_bits_count(&s->gb))>>3;
            if(i >= 0 && i <= BACKSTEP_SIZE){
                memmove(s->last_buf, s->gb.buffer + (get_bits_count(&s->gb)>>3), i);
                s->last_buf_size=i;
            }else
                av_log(NULL, AV_LOG_ERROR, "invalid old backstep %d\n", i);
            s->gb= s->in_gb;
            s->in_gb.buffer= NULL;
        }

        align_get_bits(&s->gb);
        assert((get_bits_count(&s->gb) & 7) == 0);
        i= (s->gb.size_in_bits - get_bits_count(&s->gb))>>3;

        if(i<0 || i > BACKSTEP_SIZE || nb_frames<0){
            av_log(NULL, AV_LOG_ERROR, "invalid new backstep %d\n", i);
            i= FFMIN(BACKSTEP_SIZE, buf_size - HEADER_SIZE);
        }
        assert(i <= buf_size - HEADER_SIZE && i>= 0);
        memcpy(s->last_buf + s->last_buf_size, s->gb.buffer + buf_size - HEADER_SIZE - i, i);
        s->last_buf_size += i;

        break;
    }
#if defined(DEBUG)
    for(i=0;i<nb_frames;i++) {
        for(ch=0;ch<s->nb_channels;ch++) {
            int j;
            dprintf(s->avctx, "%d-%d:", i, ch);
            for(j=0;j<SBLIMIT;j++)
                dprintf(s->avctx, " %0.6f", (double)s->sb_samples[ch][i][j] / FRAC_ONE);
            dprintf(s->avctx, "\n");
        }
    }
#endif
    /* apply the synthesis filter */
    for(ch=0;ch<s->nb_channels;ch++) {
        samples_ptr = samples + ch;
        for(i=0;i<nb_frames;i++) {
            ff_mpa_synth_filter(s->synth_buf[ch], &(s->synth_buf_offset[ch]),
                         window, &s->dither_state,
                         samples_ptr, s->nb_channels,
                         s->sb_samples[ch][i]);
            samples_ptr += 32 * s->nb_channels;
        }
    }
#ifdef DEBUG
    s->frame_count++;
#endif
    return nb_frames * 32 * sizeof(OUT_INT) * s->nb_channels;
}

static int decode_frame(AVCodecContext * avctx,
                        void *data, int *data_size,
                        const uint8_t * buf, int buf_size)
{
    MPADecodeContext *s = avctx->priv_data;
    uint32_t header;
    int out_size;
    OUT_INT *out_samples = data;

retry:
    if(buf_size < HEADER_SIZE)
        return -1;

    header = AV_RB32(buf);
    if(ff_mpa_check_header(header) < 0){
        buf++;
//        buf_size--;
        av_log(avctx, AV_LOG_ERROR, "Header missing skipping one byte.\n");
        goto retry;
    }

    if (ff_mpegaudio_decode_header(s, header) == 1) {
        /* free format: prepare to compute frame size */
        s->frame_size = -1;
        return -1;
    }
    /* update codec info */
    avctx->channels = s->nb_channels;
    avctx->bit_rate = s->bit_rate;
    avctx->sub_id = s->layer;

    if(s->frame_size<=0 || s->frame_size > buf_size){
        av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
        return -1;
    }else if(s->frame_size < buf_size){
        av_log(avctx, AV_LOG_ERROR, "incorrect frame size\n");
        buf_size= s->frame_size;
    }

    out_size = mp_decode_frame(s, out_samples, buf, buf_size);
    if(out_size>=0){
        *data_size = out_size;
        avctx->sample_rate = s->sample_rate;
        //FIXME maybe move the other codec info stuff from above here too
    }else
        av_log(avctx, AV_LOG_DEBUG, "Error while decoding MPEG audio frame.\n"); //FIXME return -1 / but also return the number of bytes consumed
    s->frame_size = 0;
    return buf_size;
}

static void flush(AVCodecContext *avctx){
    MPADecodeContext *s = avctx->priv_data;
    memset(s->synth_buf, 0, sizeof(s->synth_buf));
    s->last_buf_size= 0;
}

#ifdef CONFIG_MP3ADU_DECODER
static int decode_frame_adu(AVCodecContext * avctx,
                        void *data, int *data_size,
                        const uint8_t * buf, int buf_size)
{
    MPADecodeContext *s = avctx->priv_data;
    uint32_t header;
    int len, out_size;
    OUT_INT *out_samples = data;

    len = buf_size;

    // Discard too short frames
    if (buf_size < HEADER_SIZE) {
        *data_size = 0;
        return buf_size;
    }


    if (len > MPA_MAX_CODED_FRAME_SIZE)
        len = MPA_MAX_CODED_FRAME_SIZE;

    // Get header and restore sync word
    header = AV_RB32(buf) | 0xffe00000;

    if (ff_mpa_check_header(header) < 0) { // Bad header, discard frame
        *data_size = 0;
        return buf_size;
    }

    ff_mpegaudio_decode_header(s, header);
    /* update codec info */
    avctx->sample_rate = s->sample_rate;
    avctx->channels = s->nb_channels;
    avctx->bit_rate = s->bit_rate;
    avctx->sub_id = s->layer;

    s->frame_size = len;

    if (avctx->parse_only) {
        out_size = buf_size;
    } else {
        out_size = mp_decode_frame(s, out_samples, buf, buf_size);
    }

    *data_size = out_size;
    return buf_size;
}
#endif /* CONFIG_MP3ADU_DECODER */

#ifdef CONFIG_MP3ON4_DECODER

/**
 * Context for MP3On4 decoder
 */
typedef struct MP3On4DecodeContext {
    int frames;   ///< number of mp3 frames per block (number of mp3 decoder instances)
    int syncword; ///< syncword patch
    const uint8_t *coff; ///< channels offsets in output buffer
    MPADecodeContext *mp3decctx[5]; ///< MPADecodeContext for every decoder instance
} MP3On4DecodeContext;

#include "mpeg4audio.h"

/* Next 3 arrays are indexed by channel config number (passed via codecdata) */
static const uint8_t mp3Frames[8] = {0,1,1,2,3,3,4,5};   /* number of mp3 decoder instances */
/* offsets into output buffer, assume output order is FL FR BL BR C LFE */
static const uint8_t chan_offset[8][5] = {
    {0},
    {0},            // C
    {0},            // FLR
    {2,0},          // C FLR
    {2,0,3},        // C FLR BS
    {4,0,2},        // C FLR BLRS
    {4,0,2,5},      // C FLR BLRS LFE
    {4,0,2,6,5},    // C FLR BLRS BLR LFE
};


static int decode_init_mp3on4(AVCodecContext * avctx)
{
    MP3On4DecodeContext *s = avctx->priv_data;
    MPEG4AudioConfig cfg;
    int i;

    if ((avctx->extradata_size < 2) || (avctx->extradata == NULL)) {
        av_log(avctx, AV_LOG_ERROR, "Codec extradata missing or too short.\n");
        return -1;
    }

    ff_mpeg4audio_get_config(&cfg, avctx->extradata, avctx->extradata_size);
    if (!cfg.chan_config || cfg.chan_config > 7) {
        av_log(avctx, AV_LOG_ERROR, "Invalid channel config number.\n");
        return -1;
    }
    s->frames = mp3Frames[cfg.chan_config];
    s->coff = chan_offset[cfg.chan_config];
    avctx->channels = ff_mpeg4audio_channels[cfg.chan_config];

    if (cfg.sample_rate < 16000)
        s->syncword = 0xffe00000;
    else
        s->syncword = 0xfff00000;

    /* Init the first mp3 decoder in standard way, so that all tables get builded
     * We replace avctx->priv_data with the context of the first decoder so that
     * decode_init() does not have to be changed.
     * Other decoders will be initialized here copying data from the first context
     */
    // Allocate zeroed memory for the first decoder context
    s->mp3decctx[0] = av_mallocz(sizeof(MPADecodeContext));
    // Put decoder context in place to make init_decode() happy
    avctx->priv_data = s->mp3decctx[0];
    decode_init(avctx);
    // Restore mp3on4 context pointer
    avctx->priv_data = s;
    s->mp3decctx[0]->adu_mode = 1; // Set adu mode

    /* Create a separate codec/context for each frame (first is already ok).
     * Each frame is 1 or 2 channels - up to 5 frames allowed
     */
    for (i = 1; i < s->frames; i++) {
        s->mp3decctx[i] = av_mallocz(sizeof(MPADecodeContext));
        s->mp3decctx[i]->compute_antialias = s->mp3decctx[0]->compute_antialias;
        s->mp3decctx[i]->adu_mode = 1;
        s->mp3decctx[i]->avctx = avctx;
    }

    return 0;
}


static int decode_close_mp3on4(AVCodecContext * avctx)
{
    MP3On4DecodeContext *s = avctx->priv_data;
    int i;

    for (i = 0; i < s->frames; i++)
        if (s->mp3decctx[i])
            av_free(s->mp3decctx[i]);

    return 0;
}


static int decode_frame_mp3on4(AVCodecContext * avctx,
                        void *data, int *data_size,
                        const uint8_t * buf, int buf_size)
{
    MP3On4DecodeContext *s = avctx->priv_data;
    MPADecodeContext *m;
    int fsize, len = buf_size, out_size = 0;
    uint32_t header;
    OUT_INT *out_samples = data;
    OUT_INT decoded_buf[MPA_FRAME_SIZE * MPA_MAX_CHANNELS];
    OUT_INT *outptr, *bp;
    int fr, j, n;

    *data_size = 0;
    // Discard too short frames
    if (buf_size < HEADER_SIZE)
        return -1;

    // If only one decoder interleave is not needed
    outptr = s->frames == 1 ? out_samples : decoded_buf;

    avctx->bit_rate = 0;

    for (fr = 0; fr < s->frames; fr++) {
        fsize = AV_RB16(buf) >> 4;
        fsize = FFMIN3(fsize, len, MPA_MAX_CODED_FRAME_SIZE);
        m = s->mp3decctx[fr];
        assert (m != NULL);

        header = (AV_RB32(buf) & 0x000fffff) | s->syncword; // patch header

        if (ff_mpa_check_header(header) < 0) // Bad header, discard block
            break;

        ff_mpegaudio_decode_header(m, header);
        out_size += mp_decode_frame(m, outptr, buf, fsize);
        buf += fsize;
        len -= fsize;

        if(s->frames > 1) {
            n = m->avctx->frame_size*m->nb_channels;
            /* interleave output data */
            bp = out_samples + s->coff[fr];
            if(m->nb_channels == 1) {
                for(j = 0; j < n; j++) {
                    *bp = decoded_buf[j];
                    bp += avctx->channels;
                }
            } else {
                for(j = 0; j < n; j++) {
                    bp[0] = decoded_buf[j++];
                    bp[1] = decoded_buf[j];
                    bp += avctx->channels;
                }
            }
        }
        avctx->bit_rate += m->bit_rate;
    }

    /* update codec info */
    avctx->sample_rate = s->mp3decctx[0]->sample_rate;

    *data_size = out_size;
    return buf_size;
}
#endif /* CONFIG_MP3ON4_DECODER */

#ifdef CONFIG_MP2_DECODER
AVCodec mp2_decoder =
{
    "mp2",
    CODEC_TYPE_AUDIO,
    CODEC_ID_MP2,
    sizeof(MPADecodeContext),
    decode_init,
    NULL,
    NULL,
    decode_frame,
    CODEC_CAP_PARSE_ONLY,
    .flush= flush,
    .long_name= NULL_IF_CONFIG_SMALL("MP2 (MPEG audio layer 2)"),
};
#endif
#ifdef CONFIG_MP3_DECODER
AVCodec mp3_decoder =
{
    "mp3",
    CODEC_TYPE_AUDIO,
    CODEC_ID_MP3,
    sizeof(MPADecodeContext),
    decode_init,
    NULL,
    NULL,
    decode_frame,
    CODEC_CAP_PARSE_ONLY,
    .flush= flush,
    .long_name= NULL_IF_CONFIG_SMALL("MP3 (MPEG audio layer 3)"),
};
#endif
#ifdef CONFIG_MP3ADU_DECODER
AVCodec mp3adu_decoder =
{
    "mp3adu",
    CODEC_TYPE_AUDIO,
    CODEC_ID_MP3ADU,
    sizeof(MPADecodeContext),
    decode_init,
    NULL,
    NULL,
    decode_frame_adu,
    CODEC_CAP_PARSE_ONLY,
    .flush= flush,
    .long_name= NULL_IF_CONFIG_SMALL("ADU (Application Data Unit) MP3 (MPEG audio layer 3)"),
};
#endif
#ifdef CONFIG_MP3ON4_DECODER
AVCodec mp3on4_decoder =
{
    "mp3on4",
    CODEC_TYPE_AUDIO,
    CODEC_ID_MP3ON4,
    sizeof(MP3On4DecodeContext),
    decode_init_mp3on4,
    NULL,
    decode_close_mp3on4,
    decode_frame_mp3on4,
    .flush= flush,
    .long_name= NULL_IF_CONFIG_SMALL("MP3onMP4"),
};
#endif