static int decode_unregistered_user_data(H264Context *h, int size)
{
    uint8_t user_data[16 + 256];
    int e, build, i;

    if (size < 16)
        return AVERROR_INVALIDDATA;

    for (i = 0; i < sizeof(user_data) - 1 && i < size; i++)
        user_data[i] = get_bits(&h->gb, 8);

    user_data[i] = 0;
    e = sscanf(user_data + 16, "x264 - core %d", &build);
    if (e == 1 && build > 0)
        h->x264_build = build;

    if (h->avctx->debug & FF_DEBUG_BUGS)
        av_log(h->avctx, AV_LOG_DEBUG, "user data:\"%s\"\n", user_data + 16);

    for (; i < size; i++)
        skip_bits(&h->gb, 8);

    return 0;
}

/**
 * decodes the group of blocks / video packet header.
 * @return <0 if no resync found
 */
static int ff_h261_resync(H261Context *h){
    MpegEncContext * const s = &h->s;
    int left, ret;

    if ( h->gob_start_code_skipped ){
        ret= h261_decode_gob_header(h);
        if(ret>=0)
            return 0;
    }
    else{
        if(show_bits(&s->gb, 15)==0){
            ret= h261_decode_gob_header(h);
            if(ret>=0)
                return 0;
        }
        //OK, it is not where it is supposed to be ...
        s->gb= s->last_resync_gb;
        align_get_bits(&s->gb);
        left= s->gb.size_in_bits - get_bits_count(&s->gb);

        for(;left>15+1+4+5; left-=8){
            if(show_bits(&s->gb, 15)==0){
                GetBitContext bak= s->gb;

                ret= h261_decode_gob_header(h);
                if(ret>=0)
                    return 0;

                s->gb= bak;
            }
            skip_bits(&s->gb, 8);
        }
    }

    return -1;
}

static int decode_user_data_itu_t_t35(H264Context *h, int size)
{
    uint32_t user_identifier;
    int dtg_active_format;

    if (size < 7)
        return -1;
    size -= 7;

    skip_bits(&h->gb, 8);   // country_code
    skip_bits(&h->gb, 16);  // provider_code
    user_identifier = get_bits_long(&h->gb, 32);

    switch (user_identifier) {
        case 0x44544731:    // "DTG1" - AFD_data
            if (size < 1)
                return -1;
            skip_bits(&h->gb, 1);
            if (get_bits(&h->gb, 1)) {
                skip_bits(&h->gb, 6);
                if (size < 2)
                    return -1;
                skip_bits(&h->gb, 4);
                dtg_active_format = get_bits(&h->gb, 4);
                h->avctx->dtg_active_format = dtg_active_format;
            } else {
                skip_bits(&h->gb, 6);
            }
            break;
        default:
            skip_bits(&h->gb, size * 8);
            break;
    }

    return 0;
}

static av_cold int mpc8_decode_init(AVCodecContext * avctx)
{
    int i;
    MPCContext *c = avctx->priv_data;
    GetBitContext gb;
    static int vlc_initialized = 0;

    static VLC_TYPE band_table[542][2];
    static VLC_TYPE q1_table[520][2];
    static VLC_TYPE q9up_table[524][2];
    static VLC_TYPE scfi0_table[1 << MPC8_SCFI0_BITS][2];
    static VLC_TYPE scfi1_table[1 << MPC8_SCFI1_BITS][2];
    static VLC_TYPE dscf0_table[560][2];
    static VLC_TYPE dscf1_table[598][2];
    static VLC_TYPE q3_0_table[512][2];
    static VLC_TYPE q3_1_table[516][2];
    static VLC_TYPE codes_table[5708][2];

    if(avctx->extradata_size < 2){
        av_log(avctx, AV_LOG_ERROR, "Too small extradata size (%i)!\n", avctx->extradata_size);
        return -1;
    }
    memset(c->oldDSCF, 0, sizeof(c->oldDSCF));
    av_lfg_init(&c->rnd, 0xDEADBEEF);
    dsputil_init(&c->dsp, avctx);

    ff_mpc_init();

    init_get_bits(&gb, avctx->extradata, 16);

    skip_bits(&gb, 3);//sample rate
    c->maxbands = get_bits(&gb, 5) + 1;
    skip_bits(&gb, 4);//channels
    c->MSS = get_bits1(&gb);
    c->frames = 1 << (get_bits(&gb, 3) * 2);

    avctx->sample_fmt = SAMPLE_FMT_S16;
    avctx->channel_layout = (avctx->channels==2) ? CH_LAYOUT_STEREO : CH_LAYOUT_MONO;

    if(vlc_initialized) return 0;
    av_log(avctx, AV_LOG_DEBUG, "Initing VLC\n");

    band_vlc.table = band_table;
    band_vlc.table_allocated = 542;
    init_vlc(&band_vlc, MPC8_BANDS_BITS, MPC8_BANDS_SIZE,
             mpc8_bands_bits,  1, 1,
             mpc8_bands_codes, 1, 1, INIT_VLC_USE_NEW_STATIC);

    q1_vlc.table = q1_table;
    q1_vlc.table_allocated = 520;
    init_vlc(&q1_vlc, MPC8_Q1_BITS, MPC8_Q1_SIZE,
             mpc8_q1_bits,  1, 1,
             mpc8_q1_codes, 1, 1, INIT_VLC_USE_NEW_STATIC);
    q9up_vlc.table = q9up_table;
    q9up_vlc.table_allocated = 524;
    init_vlc(&q9up_vlc, MPC8_Q9UP_BITS, MPC8_Q9UP_SIZE,
             mpc8_q9up_bits,  1, 1,
             mpc8_q9up_codes, 1, 1, INIT_VLC_USE_NEW_STATIC);

    scfi_vlc[0].table = scfi0_table;
    scfi_vlc[0].table_allocated = 1 << MPC8_SCFI0_BITS;
    init_vlc(&scfi_vlc[0], MPC8_SCFI0_BITS, MPC8_SCFI0_SIZE,
             mpc8_scfi0_bits,  1, 1,
             mpc8_scfi0_codes, 1, 1, INIT_VLC_USE_NEW_STATIC);
    scfi_vlc[1].table = scfi1_table;
    scfi_vlc[1].table_allocated = 1 << MPC8_SCFI1_BITS;
    init_vlc(&scfi_vlc[1], MPC8_SCFI1_BITS, MPC8_SCFI1_SIZE,
             mpc8_scfi1_bits,  1, 1,
             mpc8_scfi1_codes, 1, 1, INIT_VLC_USE_NEW_STATIC);

    dscf_vlc[0].table = dscf0_table;
    dscf_vlc[0].table_allocated = 560;
    init_vlc(&dscf_vlc[0], MPC8_DSCF0_BITS, MPC8_DSCF0_SIZE,
             mpc8_dscf0_bits,  1, 1,
             mpc8_dscf0_codes, 1, 1, INIT_VLC_USE_NEW_STATIC);
    dscf_vlc[1].table = dscf1_table;
    dscf_vlc[1].table_allocated = 598;
    init_vlc(&dscf_vlc[1], MPC8_DSCF1_BITS, MPC8_DSCF1_SIZE,
             mpc8_dscf1_bits,  1, 1,
             mpc8_dscf1_codes, 1, 1, INIT_VLC_USE_NEW_STATIC);

    q3_vlc[0].table = q3_0_table;
    q3_vlc[0].table_allocated = 512;
    init_vlc_sparse(&q3_vlc[0], MPC8_Q3_BITS, MPC8_Q3_SIZE,
             mpc8_q3_bits,  1, 1,
             mpc8_q3_codes, 1, 1,
             mpc8_q3_syms,  1, 1, INIT_VLC_USE_NEW_STATIC);
    q3_vlc[1].table = q3_1_table;
    q3_vlc[1].table_allocated = 516;
    init_vlc_sparse(&q3_vlc[1], MPC8_Q4_BITS, MPC8_Q4_SIZE,
             mpc8_q4_bits,  1, 1,
             mpc8_q4_codes, 1, 1,
             mpc8_q4_syms,  1, 1, INIT_VLC_USE_NEW_STATIC);

    for(i = 0; i < 2; i++){
        res_vlc[i].table = &codes_table[vlc_offsets[0+i]];
        res_vlc[i].table_allocated = vlc_offsets[1+i] - vlc_offsets[0+i];
        init_vlc(&res_vlc[i], MPC8_RES_BITS, MPC8_RES_SIZE,
                 &mpc8_res_bits[i],  1, 1,
                 &mpc8_res_codes[i], 1, 1, INIT_VLC_USE_NEW_STATIC);
//.........这里部分代码省略.........

/* don't understand why they choose a different header ! */
int ff_intel_h263_decode_picture_header(MpegEncContext *s)
{
    int format;

    /* picture header */
    if (get_bits_long(&s->gb, 22) != 0x20) {
        av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
        return -1;
    }
    s->picture_number = get_bits(&s->gb, 8); /* picture timestamp */

    if (get_bits1(&s->gb) != 1) {
        av_log(s->avctx, AV_LOG_ERROR, "Bad marker\n");
        return -1;      /* marker */
    }
    if (get_bits1(&s->gb) != 0) {
        av_log(s->avctx, AV_LOG_ERROR, "Bad H263 id\n");
        return -1;      /* h263 id */
    }
    skip_bits1(&s->gb);         /* split screen off */
    skip_bits1(&s->gb);         /* camera  off */
    skip_bits1(&s->gb);         /* freeze picture release off */

    format = get_bits(&s->gb, 3);
    if (format == 0 || format == 6) {
        av_log(s->avctx, AV_LOG_ERROR, "Intel H263 free format not supported\n");
        return -1;
    }
    s->h263_plus = 0;

    s->pict_type = AV_PICTURE_TYPE_I + get_bits1(&s->gb);

    s->h263_long_vectors = get_bits1(&s->gb);

    if (get_bits1(&s->gb) != 0) {
        av_log(s->avctx, AV_LOG_ERROR, "SAC not supported\n");
        return -1;      /* SAC: off */
    }
    s->obmc= get_bits1(&s->gb);
    s->unrestricted_mv = s->obmc || s->h263_long_vectors;
    s->pb_frame = get_bits1(&s->gb);

    if (format < 6) {
        s->width = ff_h263_format[format][0];
        s->height = ff_h263_format[format][1];
        s->avctx->sample_aspect_ratio.num = 12;
        s->avctx->sample_aspect_ratio.den = 11;
    } else {
        format = get_bits(&s->gb, 3);
        if(format == 0 || format == 7){
            av_log(s->avctx, AV_LOG_ERROR, "Wrong Intel H263 format\n");
            return -1;
        }
        if(get_bits(&s->gb, 2))
            av_log(s->avctx, AV_LOG_ERROR, "Bad value for reserved field\n");
        s->loop_filter = get_bits1(&s->gb) * !s->avctx->lowres;
        if(get_bits1(&s->gb))
            av_log(s->avctx, AV_LOG_ERROR, "Bad value for reserved field\n");
        if(get_bits1(&s->gb))
            s->pb_frame = 2;
        if(get_bits(&s->gb, 5))
            av_log(s->avctx, AV_LOG_ERROR, "Bad value for reserved field\n");
        if(get_bits(&s->gb, 5) != 1)
            av_log(s->avctx, AV_LOG_ERROR, "Invalid marker\n");
    }
    if(format == 6){
        int ar = get_bits(&s->gb, 4);
        skip_bits(&s->gb, 9); // display width
        skip_bits1(&s->gb);
        skip_bits(&s->gb, 9); // display height
        if(ar == 15){
            s->avctx->sample_aspect_ratio.num = get_bits(&s->gb, 8); // aspect ratio - width
            s->avctx->sample_aspect_ratio.den = get_bits(&s->gb, 8); // aspect ratio - height
        } else {
            s->avctx->sample_aspect_ratio = ff_h263_pixel_aspect[ar];
        }
        if (s->avctx->sample_aspect_ratio.num == 0)
            av_log(s->avctx, AV_LOG_ERROR, "Invalid aspect ratio.\n");
    }

    s->chroma_qscale= s->qscale = get_bits(&s->gb, 5);
    skip_bits1(&s->gb); /* Continuous Presence Multipoint mode: off */

    if(s->pb_frame){
        skip_bits(&s->gb, 3); //temporal reference for B-frame
        skip_bits(&s->gb, 2); //dbquant
    }

    /* PEI */
    while (get_bits1(&s->gb) != 0) {
        skip_bits(&s->gb, 8);
    }
    s->f_code = 1;

    s->y_dc_scale_table=
    s->c_dc_scale_table= ff_mpeg1_dc_scale_table;

    ff_h263_show_pict_info(s);

//.........这里部分代码省略.........

static int mjpegb_decode_frame(AVCodecContext *avctx,
                              void *data, int *got_frame,
                              AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    MJpegDecodeContext *s = avctx->priv_data;
    const uint8_t *buf_end, *buf_ptr;
    GetBitContext hgb; /* for the header */
    uint32_t dqt_offs, dht_offs, sof_offs, sos_offs, second_field_offs;
    uint32_t field_size, sod_offs;
    int ret;

    buf_ptr = buf;
    buf_end = buf + buf_size;
    s->got_picture = 0;

read_header:
    /* reset on every SOI */
    s->restart_interval = 0;
    s->restart_count = 0;
    s->mjpb_skiptosod = 0;

    if (buf_end - buf_ptr >= 1 << 28)
        return AVERROR_INVALIDDATA;

    init_get_bits(&hgb, buf_ptr, /*buf_size*/(buf_end - buf_ptr)*8);

    skip_bits(&hgb, 32); /* reserved zeros */

    if (get_bits_long(&hgb, 32) != MKBETAG('m','j','p','g')) {
        av_log(avctx, AV_LOG_WARNING, "not mjpeg-b (bad fourcc)\n");
        return AVERROR_INVALIDDATA;
    }

    field_size = get_bits_long(&hgb, 32); /* field size */
    av_log(avctx, AV_LOG_DEBUG, "field size: 0x%"PRIx32"\n", field_size);
    skip_bits(&hgb, 32); /* padded field size */
    second_field_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "second_field_offs is %d and size is %d\n");
    av_log(avctx, AV_LOG_DEBUG, "second field offs: 0x%"PRIx32"\n",
           second_field_offs);

    dqt_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dqt is %d and size is %d\n");
    av_log(avctx, AV_LOG_DEBUG, "dqt offs: 0x%"PRIx32"\n", dqt_offs);
    if (dqt_offs) {
        init_get_bits(&s->gb, buf_ptr+dqt_offs, (buf_end - (buf_ptr+dqt_offs))*8);
        s->start_code = DQT;
        ret = ff_mjpeg_decode_dqt(s);
        if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE))
            return ret;
    }

    dht_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "dht is %d and size is %d\n");
    av_log(avctx, AV_LOG_DEBUG, "dht offs: 0x%"PRIx32"\n", dht_offs);
    if (dht_offs) {
        init_get_bits(&s->gb, buf_ptr+dht_offs, (buf_end - (buf_ptr+dht_offs))*8);
        s->start_code = DHT;
        ff_mjpeg_decode_dht(s);
    }

    sof_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
    av_log(avctx, AV_LOG_DEBUG, "sof offs: 0x%"PRIx32"\n", sof_offs);
    if (sof_offs) {
        init_get_bits(&s->gb, buf_ptr+sof_offs, (buf_end - (buf_ptr+sof_offs))*8);
        s->start_code = SOF0;
        if ((ret = ff_mjpeg_decode_sof(s)) < 0)
            return ret;
    }

    sos_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sos is %d and size is %d\n");
    av_log(avctx, AV_LOG_DEBUG, "sos offs: 0x%"PRIx32"\n", sos_offs);
    sod_offs = read_offs(avctx, &hgb, buf_end - buf_ptr, "sof is %d and size is %d\n");
    av_log(avctx, AV_LOG_DEBUG, "sod offs: 0x%"PRIx32"\n", sod_offs);
    if (sos_offs) {
        init_get_bits(&s->gb, buf_ptr + sos_offs,
                      8 * FFMIN(field_size, buf_end - buf_ptr - sos_offs));
        s->mjpb_skiptosod = (sod_offs - sos_offs - show_bits(&s->gb, 16));
        s->start_code = SOS;
        ret = ff_mjpeg_decode_sos(s, NULL, 0, NULL);
        if (ret < 0 && (avctx->err_recognition & AV_EF_EXPLODE))
            return ret;
    }

    if (s->interlaced) {
        s->bottom_field ^= 1;
        /* if not bottom field, do not output image yet */
        if (s->bottom_field != s->interlace_polarity && second_field_offs) {
            buf_ptr = buf + second_field_offs;
            goto read_header;
        }
    }

    //XXX FIXME factorize, this looks very similar to the EOI code

    if(!s->got_picture) {
        av_log(avctx, AV_LOG_WARNING, "no picture\n");
        return buf_size;
    }

    if ((ret = av_frame_ref(data, s->picture_ptr)) < 0)
//.........这里部分代码省略.........

static AVPictureType parse_picture_type(const uint8_t *buf, int buflen, CVC1HeaderParser *vc1Header)
{
  AVPictureType pictype = AV_PICTURE_TYPE_NONE;
  int skipped = 0;
  const BYTE *framestart = buf;
  if (IS_MARKER(AV_RB32(buf))) {
    framestart = NULL;
    const BYTE *start, *end, *next;
    next = buf;
    for (start = buf, end = buf + buflen; next < end; start = next) {
      if (AV_RB32(start) == VC1_CODE_FRAME) {
        framestart = start + 4;
        break;
      }
      next = find_next_marker(start + 4, end);
    }
  }
  if (framestart) {
    GetBitContext gb;
    init_get_bits(&gb, framestart, (buflen - (framestart-buf))*8);
    if (vc1Header->hdr.profile == PROFILE_ADVANCED) {
      int fcm = PROGRESSIVE;
      if (vc1Header->hdr.interlaced)
        fcm = decode012(&gb);
      if (fcm == ILACE_FIELD) {
        int fptype = get_bits(&gb, 3);
        pictype = (fptype & 2) ? AV_PICTURE_TYPE_P : AV_PICTURE_TYPE_I;
        if (fptype & 4) // B-picture
          pictype = (fptype & 2) ? AV_PICTURE_TYPE_BI : AV_PICTURE_TYPE_B;
      } else {
        switch (get_unary(&gb, 0, 4)) {
        case 0:
            pictype = AV_PICTURE_TYPE_P;
            break;
        case 1:
            pictype = AV_PICTURE_TYPE_B;
            break;
        case 2:
            pictype = AV_PICTURE_TYPE_I;
            break;
        case 3:
            pictype = AV_PICTURE_TYPE_BI;
            break;
        case 4:
            pictype = AV_PICTURE_TYPE_P; // skipped pic
            skipped = 1;
            break;
        }
      }
    } else {
      if (vc1Header->hdr.finterp)
        skip_bits1(&gb);
      skip_bits(&gb, 2); // framecnt
      if (vc1Header->hdr.rangered)
        skip_bits1(&gb);
      int pic = get_bits1(&gb);
      if (vc1Header->hdr.bframes) {
        if (!pic) {
          if (get_bits1(&gb)) {
            pictype = AV_PICTURE_TYPE_I;
          } else {
            pictype = AV_PICTURE_TYPE_B;
          }
        } else {
          pictype = AV_PICTURE_TYPE_P;
        }
      } else {
        pictype = pic ? AV_PICTURE_TYPE_P : AV_PICTURE_TYPE_I;
      }
    }
  }
  return pictype;
}

/* most is hardcoded. should extend to handle all h263 streams */
static int h263_decode_picture_header(unsigned char *b_ptr)
{
//    int i;
        
//    for(i=0;i<16;i++) printf(" %02X",b_ptr[i]); printf("\n");
    
    buffer=b_ptr;
    bufptr=bitcnt=buf=0;

    /* picture header */
    if (get_bits(&s->gb, 22) != 0x20){
	mp_msg(MSGT_DEMUX, MSGL_FATAL, "bad picture header\n");
        return -1;
    }
    skip_bits(&s->gb, 8); /* picture timestamp */

    if (get_bits1(&s->gb) != 1){
	mp_msg(MSGT_DEMUX, MSGL_FATAL, "bad marker\n");
        return -1;	/* marker */
    }
    if (get_bits1(&s->gb) != 0){
	mp_msg(MSGT_DEMUX, MSGL_FATAL, "bad h263 id\n");
        return -1;	/* h263 id */
    }
    skip_bits1(&s->gb);	/* split screen off */
    skip_bits1(&s->gb);	/* camera  off */
    skip_bits1(&s->gb);	/* freeze picture release off */

    format = get_bits(&s->gb, 3);

    if (format != 7) {
        mp_msg(MSGT_DEMUX, MSGL_V, "h263_plus = 0  format = %d\n", format);
        /* H.263v1 */
        width = h263_format[format][0];
        height = h263_format[format][1];
	mp_msg(MSGT_DEMUX, MSGL_V, "%d x %d\n", width, height);
//        if (!width) return -1;

	mp_msg(MSGT_DEMUX, MSGL_V, "pict_type=%d\n", get_bits1(&s->gb));
	mp_msg(MSGT_DEMUX, MSGL_V, "unrestricted_mv=%d\n", get_bits1(&s->gb));
#if 1
	mp_msg(MSGT_DEMUX, MSGL_V, "SAC: %d\n", get_bits1(&s->gb));
	mp_msg(MSGT_DEMUX, MSGL_V, "advanced prediction mode: %d\n", get_bits1(&s->gb));
	mp_msg(MSGT_DEMUX, MSGL_V, "PB frame: %d\n", get_bits1(&s->gb));
#else
        if (get_bits1(&s->gb) != 0)
            return -1;	/* SAC: off */
        if (get_bits1(&s->gb) != 0)
            return -1;	/* advanced prediction mode: off */
        if (get_bits1(&s->gb) != 0)
            return -1;	/* not PB frame */
#endif
	mp_msg(MSGT_DEMUX, MSGL_V, "qscale=%d\n", get_bits(&s->gb, 5));
        skip_bits1(&s->gb);	/* Continuous Presence Multipoint mode: off */
    } else {
        mp_msg(MSGT_DEMUX, MSGL_V, "h263_plus = 1\n");
        /* H.263v2 */
        if (get_bits(&s->gb, 3) != 1){
	    mp_msg(MSGT_DEMUX, MSGL_FATAL, "H.263v2 A error\n");
            return -1;
	}
        if (get_bits(&s->gb, 3) != 6){ /* custom source format */
	    mp_msg(MSGT_DEMUX, MSGL_FATAL, "custom source format\n");
            return -1;
	}
        skip_bits(&s->gb, 12);
        skip_bits(&s->gb, 3);
	mp_msg(MSGT_DEMUX, MSGL_V, "pict_type=%d\n", get_bits(&s->gb, 3) + 1);
//        if (s->pict_type != I_TYPE &&
//            s->pict_type != P_TYPE)
//            return -1;
        skip_bits(&s->gb, 7);
        skip_bits(&s->gb, 4); /* aspect ratio */
        width = (get_bits(&s->gb, 9) + 1) * 4;
        skip_bits1(&s->gb);
        height = get_bits(&s->gb, 9) * 4;
	mp_msg(MSGT_DEMUX, MSGL_V, "%d x %d\n", width, height);
        //if (height == 0)
        //    return -1;
	mp_msg(MSGT_DEMUX, MSGL_V, "qscale=%d\n", get_bits(&s->gb, 5));
    }

    /* PEI */
    while (get_bits1(&s->gb) != 0) {
        skip_bits(&s->gb, 8);
    }
//    s->f_code = 1;
//    s->width = width;
//    s->height = height;
    return 0;
}

static int read_stream_mux_config(struct LATMContext *latmctx,
                                  GetBitContext *gb)
{
    int ret, audio_mux_version = get_bits(gb, 1);

    latmctx->audio_mux_version_A = 0;
    if (audio_mux_version)
        latmctx->audio_mux_version_A = get_bits(gb, 1);

    if (!latmctx->audio_mux_version_A) {

        if (audio_mux_version)
            latm_get_value(gb);                 // taraFullness

        skip_bits(gb, 1);                       // allStreamSameTimeFraming
        skip_bits(gb, 6);                       // numSubFrames
        // numPrograms
        if (get_bits(gb, 4)) {                  // numPrograms
            avpriv_request_sample(latmctx->aac_ctx.avctx, "Multiple programs");
            return AVERROR_PATCHWELCOME;
        }

        // for each program (which there is only one in DVB)

        // for each layer (which there is only one in DVB)
        if (get_bits(gb, 3)) {                   // numLayer
            avpriv_request_sample(latmctx->aac_ctx.avctx, "Multiple layers");
            return AVERROR_PATCHWELCOME;
        }

        // for all but first stream: use_same_config = get_bits(gb, 1);
        if (!audio_mux_version) {
            if ((ret = latm_decode_audio_specific_config(latmctx, gb, 0)) < 0)
                return ret;
        } else {
            int ascLen = latm_get_value(gb);
            if ((ret = latm_decode_audio_specific_config(latmctx, gb, ascLen)) < 0)
                return ret;
            ascLen -= ret;
            skip_bits_long(gb, ascLen);
        }

        latmctx->frame_length_type = get_bits(gb, 3);
        switch (latmctx->frame_length_type) {
        case 0:
            skip_bits(gb, 8);       // latmBufferFullness
            break;
        case 1:
            latmctx->frame_length = get_bits(gb, 9);
            break;
        case 3:
        case 4:
        case 5:
            skip_bits(gb, 6);       // CELP frame length table index
            break;
        case 6:
        case 7:
            skip_bits(gb, 1);       // HVXC frame length table index
            break;
        }

        if (get_bits(gb, 1)) {                  // other data
            if (audio_mux_version) {
                latm_get_value(gb);             // other_data_bits
            } else {
                int esc;
                do {
                    esc = get_bits(gb, 1);
                    skip_bits(gb, 8);
                } while (esc);
            }
        }

        if (get_bits(gb, 1))                     // crc present
            skip_bits(gb, 8);                    // config_crc
    }

    return 0;
}

/**
 * read the next MVs for OBMC. yes this is a ugly hack, feel free to send a patch :)
 */
static void preview_obmc(MpegEncContext *s){
    GetBitContext gb= s->gb;

    int cbpc, i, pred_x, pred_y, mx, my;
    int16_t *mot_val;
    const int xy= s->mb_x + 1 + s->mb_y * s->mb_stride;
    const int stride= s->b8_stride*2;

    for(i=0; i<4; i++)
        s->block_index[i]+= 2;
    for(i=4; i<6; i++)
        s->block_index[i]+= 1;
    s->mb_x++;

    av_assert2(s->pict_type == AV_PICTURE_TYPE_P);

    do{
        if (get_bits1(&s->gb)) {
            /* skip mb */
            mot_val = s->current_picture.motion_val[0][s->block_index[0]];
            mot_val[0       ]= mot_val[2       ]=
            mot_val[0+stride]= mot_val[2+stride]= 0;
            mot_val[1       ]= mot_val[3       ]=
            mot_val[1+stride]= mot_val[3+stride]= 0;

            s->current_picture.mb_type[xy] = MB_TYPE_SKIP | MB_TYPE_16x16 | MB_TYPE_L0;
            goto end;
        }
        cbpc = get_vlc2(&s->gb, ff_h263_inter_MCBPC_vlc.table, INTER_MCBPC_VLC_BITS, 2);
    }while(cbpc == 20);

    if(cbpc & 4){
        s->current_picture.mb_type[xy] = MB_TYPE_INTRA;
    }else{
        get_vlc2(&s->gb, ff_h263_cbpy_vlc.table, CBPY_VLC_BITS, 1);
        if (cbpc & 8) {
            if(s->modified_quant){
                if(get_bits1(&s->gb)) skip_bits(&s->gb, 1);
                else                  skip_bits(&s->gb, 5);
            }else
                skip_bits(&s->gb, 2);
        }

        if ((cbpc & 16) == 0) {
                s->current_picture.mb_type[xy] = MB_TYPE_16x16 | MB_TYPE_L0;
                /* 16x16 motion prediction */
                mot_val= ff_h263_pred_motion(s, 0, 0, &pred_x, &pred_y);
                if (s->umvplus)
                   mx = h263p_decode_umotion(s, pred_x);
                else
                   mx = ff_h263_decode_motion(s, pred_x, 1);

                if (s->umvplus)
                   my = h263p_decode_umotion(s, pred_y);
                else
                   my = ff_h263_decode_motion(s, pred_y, 1);

                mot_val[0       ]= mot_val[2       ]=
                mot_val[0+stride]= mot_val[2+stride]= mx;
                mot_val[1       ]= mot_val[3       ]=
                mot_val[1+stride]= mot_val[3+stride]= my;
        } else {
            s->current_picture.mb_type[xy] = MB_TYPE_8x8 | MB_TYPE_L0;
            for(i=0;i<4;i++) {
                mot_val = ff_h263_pred_motion(s, i, 0, &pred_x, &pred_y);
                if (s->umvplus)
                  mx = h263p_decode_umotion(s, pred_x);
                else
                  mx = ff_h263_decode_motion(s, pred_x, 1);

                if (s->umvplus)
                  my = h263p_decode_umotion(s, pred_y);
                else
                  my = ff_h263_decode_motion(s, pred_y, 1);
                if (s->umvplus && (mx - pred_x) == 1 && (my - pred_y) == 1)
                  skip_bits1(&s->gb); /* Bit stuffing to prevent PSC */
                mot_val[0] = mx;
                mot_val[1] = my;
            }
        }
    }
end:

    for(i=0; i<4; i++)
        s->block_index[i]-= 2;
    for(i=4; i<6; i++)
        s->block_index[i]-= 1;
    s->mb_x--;

    s->gb= gb;
}

/**
 * decodes a macroblock
 * @return <0 if an error occurred
 */
static int h261_decode_block(H261Context * h, DCTELEM * block,
                             int n, int coded)
{
    MpegEncContext * const s = &h->s;
    int code, level, i, j, run;
    RLTable *rl = &h261_rl_tcoeff;
    const uint8_t *scan_table;

    // For the variable length encoding there are two code tables, one being used for
    // the first transmitted LEVEL in INTER, INTER+MC and INTER+MC+FIL blocks, the second
    // for all other LEVELs except the first one in INTRA blocks which is fixed length
    // coded with 8 bits.
    // NOTE: the two code tables only differ in one VLC so we handle that manually.
    scan_table = s->intra_scantable.permutated;
    if (s->mb_intra){
        /* DC coef */
        level = get_bits(&s->gb, 8);
        // 0 (00000000b) and -128 (10000000b) are FORBIDDEN
        if((level&0x7F) == 0){
            av_log(s->avctx, AV_LOG_ERROR, "illegal dc %d at %d %d\n", level, s->mb_x, s->mb_y);
            return -1;
        }
        // The code 1000 0000 is not used, the reconstruction level of 1024 being coded as 1111 1111.
        if (level == 255)
            level = 128;
        block[0] = level;
        i = 1;
    }else if(coded){
        // Run  Level   Code
        // EOB                  Not possible for first level when cbp is available (that's why the table is different)
        // 0    1               1s
        // *    *               0*
        int check = show_bits(&s->gb, 2);
        i = 0;
        if ( check & 0x2 ){
            skip_bits(&s->gb, 2);
            block[0] = ( check & 0x1 ) ? -1 : 1;
            i = 1;
        }
    }else{
        i = 0;
    }
    if(!coded){
        s->block_last_index[n] = i - 1;
        return 0;
    }
    for(;;){
        code = get_vlc2(&s->gb, rl->vlc.table, TCOEFF_VLC_BITS, 2);
        if (code < 0){
            av_log(s->avctx, AV_LOG_ERROR, "illegal ac vlc code at %dx%d\n", s->mb_x, s->mb_y);
            return -1;
        }
        if (code == rl->n) {
            /* escape */
            // The remaining combinations of (run, level) are encoded with a 20-bit word consisting of 6 bits escape, 6 bits run and 8 bits level.
            run = get_bits(&s->gb, 6);
            level = get_sbits(&s->gb, 8);
        }else if(code == 0){
            break;
        }else{
            run = rl->table_run[code];
            level = rl->table_level[code];
            if (get_bits1(&s->gb))
                level = -level;
        }
        i += run;
        if (i >= 64){
            av_log(s->avctx, AV_LOG_ERROR, "run overflow at %dx%d\n", s->mb_x, s->mb_y);
            return -1;
        }
        j = scan_table[i];
        block[j] = level;
        i++;
    }
    s->block_last_index[n] = i-1;
    return 0;
}

// Return TRUE if the data parsing finished, FALSE otherwise.
// estream->pos is advanced. Data is only processed if esstream->error
// is FALSE, parsing can set esstream->error to TRUE.
static int gop_header(struct bitstream *esstream)
{
    dbg_print(DMT_VERBOSE, "GOP header\n");

    if (esstream->error || esstream->bitsleft <= 0)
        return 0;

    // We only get here after seeing that start code
    if (read_u32(esstream) != 0xB8010000) // LSB first (0x000001B8)
        fatal(EXIT_BUG_BUG, "Impossible!");

    unsigned drop_frame_flag = (unsigned) read_bits(esstream,1);
    struct gop_time_code gtc;
    gtc.time_code_hours = (int) read_bits(esstream,5);
    gtc.time_code_minutes = (int) read_bits(esstream,6);
    skip_bits(esstream,1); // Marker bit
    gtc.time_code_seconds = (int) read_bits(esstream,6);
    gtc.time_code_pictures = (int) read_bits(esstream,6);
    gtc.inited = 1;
    calculate_ms_gop_time(&gtc);

    if (esstream->bitsleft < 0)
        return 0;

    if (gop_accepted(&gtc))
    {
        // Do GOP padding during GOP header. The previous GOP and all
        // included captions are written. Use the current GOP time to
        // do the padding.

        // Flush buffered cc blocks before doing the housekeeping
        if (has_ccdata_buffered)
        {
            process_hdcc();
        }

        // Last GOPs pulldown frames
        if ((current_pulldownfields>0) != (pulldownfields>0))
        {
            current_pulldownfields = pulldownfields;
            dbg_print(DMT_VERBOSE, "Pulldown: %s", (pulldownfields ? "on" : "off"));
            if (pulldownfields)
                dbg_print(DMT_VERBOSE, " - %u fields in last GOP", pulldownfields);
            dbg_print(DMT_VERBOSE, "\n");
        }
        pulldownfields = 0;

        // Report synchronization jumps between GOPs. Warn if there
        // are 20% or more deviation.
        if ( (debug_mask & DMT_TIME)
             && ((gtc.ms - gop_time.ms // more than 20% longer
                  > frames_since_last_gop*1000.0/current_fps*1.2)
                 ||
                 (gtc.ms - gop_time.ms // or 20% shorter
                  < frames_since_last_gop*1000.0/current_fps*0.8))
             && first_gop_time.inited )
        {
            mprint("\rWarning: Jump in GOP timing.\n");
            mprint("  (old) %s",
                   print_mstime(gop_time.ms));
            mprint("  +  %s (%uF)",
                   print_mstime(LLONG(frames_since_last_gop
                                      *1000.0/current_fps)),
                   frames_since_last_gop);
            mprint("  !=  (new) %s\n",
                   print_mstime(gtc.ms));
        }

        if (first_gop_time.inited == 0)
        {
            first_gop_time = gtc;

            // It needs to be "+1" because the frame count starts at 0 and we
            // need the length of all frames.
            if ( total_frames_count == 0 )
            {   // If this is the first frame there cannot be an offset
                fts_fc_offset = 0;
                // first_gop_time.ms stays unchanged
            }
            else
            {
                fts_fc_offset = LLONG((total_frames_count+1)
                                      *1000.0/current_fps);
                // Compensate for those written before
                first_gop_time.ms -= fts_fc_offset;
            }

            dbg_print(DMT_TIME, "\nFirst GOP time: %02u:%02u:%02u:%03u %+lldms\n",
                    gtc.time_code_hours,
                    gtc.time_code_minutes, gtc.time_code_seconds,
                    unsigned(1000.0*gtc.time_code_pictures/current_fps),
                    fts_fc_offset);
        }

        gop_time = gtc;

        frames_since_last_gop=0;
//.........这里部分代码省略.........

static int decode_picture_timing(H264Context *h)
{
    SPS *sps = &h->sps;
    int i;

    for (i = 0; i<MAX_SPS_COUNT; i++)
        if (!sps->log2_max_frame_num && h->sps_buffers[i])
            sps = h->sps_buffers[i];

    if (sps->nal_hrd_parameters_present_flag || sps->vcl_hrd_parameters_present_flag) {
        h->sei_cpb_removal_delay = get_bits_long(&h->gb,
                                                 sps->cpb_removal_delay_length);
        h->sei_dpb_output_delay  = get_bits_long(&h->gb,
                                                 sps->dpb_output_delay_length);
    }
    if (sps->pic_struct_present_flag) {
        unsigned int i, num_clock_ts;

        h->sei_pic_struct = get_bits(&h->gb, 4);
        h->sei_ct_type    = 0;

        if (h->sei_pic_struct > SEI_PIC_STRUCT_FRAME_TRIPLING)
            return AVERROR_INVALIDDATA;

        num_clock_ts = sei_num_clock_ts_table[h->sei_pic_struct];

        for (i = 0; i < num_clock_ts; i++) {
            if (get_bits(&h->gb, 1)) {                /* clock_timestamp_flag */
                unsigned int full_timestamp_flag;

                h->sei_ct_type |= 1 << get_bits(&h->gb, 2);
                skip_bits(&h->gb, 1);                 /* nuit_field_based_flag */
                skip_bits(&h->gb, 5);                 /* counting_type */
                full_timestamp_flag = get_bits(&h->gb, 1);
                skip_bits(&h->gb, 1);                 /* discontinuity_flag */
                skip_bits(&h->gb, 1);                 /* cnt_dropped_flag */
                skip_bits(&h->gb, 8);                 /* n_frames */
                if (full_timestamp_flag) {
                    skip_bits(&h->gb, 6);             /* seconds_value 0..59 */
                    skip_bits(&h->gb, 6);             /* minutes_value 0..59 */
                    skip_bits(&h->gb, 5);             /* hours_value 0..23 */
                } else {
                    if (get_bits(&h->gb, 1)) {        /* seconds_flag */
                        skip_bits(&h->gb, 6);         /* seconds_value range 0..59 */
                        if (get_bits(&h->gb, 1)) {    /* minutes_flag */
                            skip_bits(&h->gb, 6);     /* minutes_value 0..59 */
                            if (get_bits(&h->gb, 1))  /* hours_flag */
                                skip_bits(&h->gb, 5); /* hours_value 0..23 */
                        }
                    }
                }
                if (sps->time_offset_length > 0)
                    skip_bits(&h->gb,
                              sps->time_offset_length); /* time_offset */
            }
        }

        if (h->avctx->debug & FF_DEBUG_PICT_INFO)
            av_log(h->avctx, AV_LOG_DEBUG, "ct_type:%X pic_struct:%d\n",
                   h->sei_ct_type, h->sei_pic_struct);
    }
    return 0;
}

// Return TRUE if the data parsing finished, FALSE otherwise.
// estream->pos is advanced. Data is only processed if esstream->error
// is FALSE, parsing can set esstream->error to TRUE.
static int sequence_header(struct bitstream *esstream)
{
    dbg_print(DMT_VERBOSE, "Sequence header\n");

    if (esstream->error || esstream->bitsleft <= 0)
        return 0;

    // We only get here after seeing that start code
    if (read_u32(esstream) != 0xB3010000) // LSB first (0x000001B3)
        fatal(EXIT_BUG_BUG, "Impossible!");

    unsigned hor_size = (unsigned) read_bits(esstream,12);
    unsigned vert_size = (unsigned) read_bits(esstream,12);
    unsigned aspect_ratio = (unsigned) read_bits(esstream,4);
    unsigned frame_rate = (unsigned) read_bits(esstream,4);

    // Discard some information
    read_bits(esstream, 18+1+10+1);

    // load_intra_quantiser_matrix
    if (read_bits(esstream,1))
        skip_bits(esstream, 8*64);
    // load_non_intra_quantiser_matrix
    if (read_bits(esstream,1))
        skip_bits(esstream, 8*64);

    if (esstream->bitsleft < 0)
        return 0;

    // If we got the whole sequence, process
    if (hor_size!=current_hor_size ||
        vert_size!=current_vert_size ||
        aspect_ratio!=current_aspect_ratio ||
        frame_rate!=current_frame_rate)
    {
        // If horizontal/vertical size, framerate and/or aspect
        // ratio are ilegal, we discard the
        // whole sequence info.
        if (vert_size >= 288 && vert_size <= 1088 && 
            hor_size >= 352 && hor_size <= 1920 &&
            hor_size / vert_size >= 352/576 && hor_size / vert_size <= 2 &&
            frame_rate>0 && frame_rate<9 &&
            aspect_ratio>0 && aspect_ratio<5)
        {
            mprint ("\n\nNew video information found");
            if (pts_set==2)
            {
                unsigned cur_sec = (unsigned) ((current_pts - min_pts)
                                               / MPEG_CLOCK_FREQ);
                mprint (" at %02u:%02u",cur_sec/60, cur_sec % 60);
            }
            mprint ("\n");                                          
            mprint ("[%u * %u] [AR: %s] [FR: %s]",
                    hor_size,vert_size,
                    aspect_ratio_types[aspect_ratio],
                    framerates_types[frame_rate]);
            // No newline, force the output of progressive info in picture
            // info part.
            current_progressive_sequence = 2;

            current_hor_size=hor_size;
            current_vert_size=vert_size;
            current_aspect_ratio=aspect_ratio;
            current_frame_rate=frame_rate;
            current_fps = framerates_values[current_frame_rate];
            activity_video_info (hor_size,vert_size,
                                 aspect_ratio_types[aspect_ratio],
                                 framerates_types[frame_rate]);
        } 
        else 
        {
            dbg_print(DMT_VERBOSE, "\nInvalid sequence header:\n");
            dbg_print(DMT_VERBOSE, "V: %u H: %u FR: %u AS: %u\n",
                   vert_size, hor_size, frame_rate, aspect_ratio);
            esstream->error = 1;
            return 0;
        }
    }

    // Read complete
    return 1;
}

// Return TRUE if the video sequence was finished, FALSE
// Otherwise.  estream->pos shall point to the position where
// the next call will continue, i.e. the possible begin of an
// unfinished video sequence or after the finished sequence.
static int es_video_sequence(struct bitstream *esstream)
{
    // Avoid "Skip forward" message on first call and later only
    // once per search.
    static int noskipmessage = 1;
    uint8_t startcode;

    dbg_print(DMT_VERBOSE, "es_video_sequence()\n");

    esstream->error = 0;

    // Analyze sequence header ...
    if (!no_bitstream_error)
    {
        // We might start here because of a syntax error. Discard
        // all data until a new sequence_header_code or group_start_code
        // is found.

        if (!noskipmessage) // Avoid unnecessary output.
            mprint("\nSkip forward to the next Sequence or GOP start.\n");
        else
            noskipmessage = 0;

        uint8_t startcode;
        while(1)
        {
            // search_start_code() cannot produce esstream->error
            startcode = search_start_code(esstream);
            if (esstream->bitsleft < 0)
            {
                noskipmessage = 1;
                return 0;
            }

            if (startcode == 0xB3 || startcode == 0xB8) // found it
                break;

            skip_bits(esstream, 4*8);
        }

        no_bitstream_error = 1;
        saw_seqgoppic = 0;
        in_pic_data = 0;
    }

    do
    {
        startcode = next_start_code(esstream);

        dbg_print(DMT_VERBOSE, "\nM2V - next start code %02X %d\n", startcode, in_pic_data);

        // Syntax check - also returns on bitsleft < 0
        if (startcode == 0xB4)
        {
            if (esstream->error)
            {
                no_bitstream_error = 0;
                dbg_print(DMT_VERBOSE, "es_video_sequence: syntax problem.\n");
            }

            dbg_print(DMT_VERBOSE, "es_video_sequence: return on B4 startcode.\n");

            return 0;
        }

        // Sequence_end_code
        if (startcode == 0xB7)
        {
            read_u32(esstream); // Advance bitstream
            no_bitstream_error = 0;
            break;
        }

        if (!in_pic_data && startcode == 0xB3)
        {
            if (!read_seq_info(esstream))
            {
                if (esstream->error)
                    no_bitstream_error = 0;
                return 0;
            }
            saw_seqgoppic = 1;
            continue;
        }

        if (!in_pic_data && startcode == 0xB8)
        {
            if (!read_gop_info(esstream))
            {
                if (esstream->error)
                    no_bitstream_error = 0;
                return 0;
            }
            saw_seqgoppic = 2;
            continue;
        }
//.........这里部分代码省略.........