C++ skip_bits_long函数代码示例

void ff_flac_parse_streaminfo(AVCodecContext *avctx, struct FLACStreaminfo *s,
                              const uint8_t *buffer)
{
    GetBitContext gb;
    init_get_bits(&gb, buffer, FLAC_STREAMINFO_SIZE*8);

    skip_bits(&gb, 16); /* skip min blocksize */
    s->max_blocksize = get_bits(&gb, 16);
    if (s->max_blocksize < FLAC_MIN_BLOCKSIZE) {
        av_log(avctx, AV_LOG_WARNING, "invalid max blocksize: %d\n",
               s->max_blocksize);
        s->max_blocksize = 16;
    }

    skip_bits(&gb, 24); /* skip min frame size */
    s->max_framesize = get_bits_long(&gb, 24);

    s->samplerate = get_bits_long(&gb, 20);
    s->channels = get_bits(&gb, 3) + 1;
    s->bps = get_bits(&gb, 5) + 1;

    avctx->channels = s->channels;
    avctx->sample_rate = s->samplerate;
    avctx->bits_per_raw_sample = s->bps;

    s->samples  = get_bits_long(&gb, 32) << 4;
    s->samples |= get_bits(&gb, 4);

    skip_bits_long(&gb, 64); /* md5 sum */
    skip_bits_long(&gb, 64); /* md5 sum */

    dump_headers(avctx, s);
}

static int
flac_header (AVFormatContext *s, int idx)
{
    struct ogg *ogg = s->priv_data;
    struct ogg_stream *os = ogg->streams + idx;
    AVStream *st = s->streams[idx];
    GetBitContext gb;
    FLACStreaminfo si;
    int mdt;

    if (os->buf[os->pstart] == 0xff)
        return 0;

    init_get_bits(&gb, os->buf + os->pstart, os->psize * 8);
    skip_bits1(&gb); /* metadata_last */
    mdt = get_bits(&gb, 7);

    if (mdt == OGG_FLAC_METADATA_TYPE_STREAMINFO)
    {
        uint8_t *streaminfo_start = os->buf + os->pstart + 5 + 4 + 4 + 4;
        skip_bits_long(&gb, 4 * 8); /* "FLAC" */
        if(get_bits(&gb, 8) != 1) /* unsupported major version */
            return -1;
        skip_bits_long(&gb, 8 + 16); /* minor version + header count */
        skip_bits_long(&gb, 4 * 8); /* "fLaC" */

        /* METADATA_BLOCK_HEADER */
        if (get_bits_long(&gb, 32) != FLAC_STREAMINFO_SIZE)
            return -1;

        ff_flac_parse_streaminfo(st->codec, &si, streaminfo_start);

        st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
        st->codec->codec_id = CODEC_ID_FLAC;

        st->codec->extradata =
            av_malloc(FLAC_STREAMINFO_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
        memcpy(st->codec->extradata, streaminfo_start, FLAC_STREAMINFO_SIZE);
        st->codec->extradata_size = FLAC_STREAMINFO_SIZE;

        av_set_pts_info(st, 64, 1, st->codec->sample_rate);
    }
    else if (mdt == FLAC_METADATA_TYPE_VORBIS_COMMENT)
    {
        ff_vorbis_comment (s, &st->metadata, os->buf + os->pstart + 4, os->psize - 4);
    }

    return 1;
}

static int decode_nal_sei_prefix(GetBitContext *gb, void *logctx, HEVCSEI *s,
                                 const HEVCParamSets *ps, int type, int size)
{
    switch (type) {
    case 256:  // Mismatched value from HM 8.1
        return decode_nal_sei_decoded_picture_hash(&s->picture_hash, gb);
    case HEVC_SEI_TYPE_FRAME_PACKING:
        return decode_nal_sei_frame_packing_arrangement(&s->frame_packing, gb);
    case HEVC_SEI_TYPE_DISPLAY_ORIENTATION:
        return decode_nal_sei_display_orientation(&s->display_orientation, gb);
    case HEVC_SEI_TYPE_PICTURE_TIMING:
        return decode_nal_sei_pic_timing(s, gb, ps, logctx, size);
    case HEVC_SEI_TYPE_MASTERING_DISPLAY_INFO:
        return decode_nal_sei_mastering_display_info(&s->mastering_display, gb);
    case HEVC_SEI_TYPE_CONTENT_LIGHT_LEVEL_INFO:
        return decode_nal_sei_content_light_info(&s->content_light, gb);
    case HEVC_SEI_TYPE_ACTIVE_PARAMETER_SETS:
        return decode_nal_sei_active_parameter_sets(s, gb, logctx);
    case HEVC_SEI_TYPE_USER_DATA_REGISTERED_ITU_T_T35:
        return decode_nal_sei_user_data_registered_itu_t_t35(s, gb, size);
    case HEVC_SEI_TYPE_ALTERNATIVE_TRANSFER_CHARACTERISTICS:
        return decode_nal_sei_alternative_transfer(&s->alternative_transfer, gb);
    default:
        av_log(logctx, AV_LOG_DEBUG, "Skipped PREFIX SEI %d\n", type);
        skip_bits_long(gb, 8 * size);
        return 0;
    }
}

static int decode_nal_sei_pic_timing(HEVCSEI *s, GetBitContext *gb, const HEVCParamSets *ps,
                                     void *logctx, int size)
{
    HEVCSEIPictureTiming *h = &s->picture_timing;
    HEVCSPS *sps;

    if (!ps->sps_list[s->active_seq_parameter_set_id])
        return(AVERROR(ENOMEM));
    sps = (HEVCSPS*)ps->sps_list[s->active_seq_parameter_set_id]->data;

    if (sps->vui.frame_field_info_present_flag) {
        int pic_struct = get_bits(gb, 4);
        h->picture_struct = AV_PICTURE_STRUCTURE_UNKNOWN;
        if (pic_struct == 2 || pic_struct == 10 || pic_struct == 12) {
            av_log(logctx, AV_LOG_DEBUG, "BOTTOM Field\n");
            h->picture_struct = AV_PICTURE_STRUCTURE_BOTTOM_FIELD;
        } else if (pic_struct == 1 || pic_struct == 9 || pic_struct == 11) {
            av_log(logctx, AV_LOG_DEBUG, "TOP Field\n");
            h->picture_struct = AV_PICTURE_STRUCTURE_TOP_FIELD;
        }
        get_bits(gb, 2);                   // source_scan_type
        get_bits(gb, 1);                   // duplicate_flag
        skip_bits1(gb);
        size--;
    }
    skip_bits_long(gb, 8 * size);

    return 0;
}

static int decode_pic_timing(HEVCContext *s, int size)
{
    GetBitContext *gb = &s->HEVClc->gb;
    HEVCSPS *sps;

    if (!s->ps.sps_list[s->active_seq_parameter_set_id])
        return(AVERROR(ENOMEM));
    sps = (HEVCSPS*)s->ps.sps_list[s->active_seq_parameter_set_id]->data;

    if (sps->vui.frame_field_info_present_flag) {
        int pic_struct = get_bits(gb, 4);
        s->picture_struct = AV_PICTURE_STRUCTURE_UNKNOWN;
        if (pic_struct == 2) {
            av_log(s->avctx, AV_LOG_DEBUG, "BOTTOM Field\n");
            s->picture_struct = AV_PICTURE_STRUCTURE_BOTTOM_FIELD;
        } else if (pic_struct == 1) {
            av_log(s->avctx, AV_LOG_DEBUG, "TOP Field\n");
            s->picture_struct = AV_PICTURE_STRUCTURE_TOP_FIELD;
        }
        get_bits(gb, 2);                   // source_scan_type
        get_bits(gb, 1);                   // duplicate_flag
        skip_bits1(gb);
        size--;
    }
    skip_bits_long(gb, 8 * size);

    return 0;
}

static int decode_nal_sei_prefix(HEVCContext *s, int type, int size)
{
    GetBitContext *gb = &s->HEVClc->gb;

    switch (type) {
    case 256:  // Mismatched value from HM 8.1
        return decode_nal_sei_decoded_picture_hash(s);
    case SEI_TYPE_FRAME_PACKING:
        return decode_nal_sei_frame_packing_arrangement(s);
    case SEI_TYPE_DISPLAY_ORIENTATION:
        return decode_nal_sei_display_orientation(s);
    case SEI_TYPE_PICTURE_TIMING:
        {
            int ret = decode_pic_timing(s);
            av_log(s->avctx, AV_LOG_DEBUG, "Skipped PREFIX SEI %d\n", type);
            skip_bits(gb, 8 * size);
            return ret;
        }
    case SEI_TYPE_ACTIVE_PARAMETER_SETS:
        active_parameter_sets(s);
        av_log(s->avctx, AV_LOG_DEBUG, "Skipped PREFIX SEI %d\n", type);
        return 0;
    case SEI_TYPE_USER_DATA_REGISTERED_ITU_T_T35:
        return decode_nal_sei_user_data_registered_itu_t_t35(s, size);
    default:
        av_log(s->avctx, AV_LOG_DEBUG, "Skipped PREFIX SEI %d\n", type);
        skip_bits_long(gb, 8 * size);
        return 0;
    }
}

static int decode_nal_sei_user_data_registered_itu_t_t35(HEVCContext *s, int size)
{
    uint32_t country_code;
    uint32_t user_identifier;

    GetBitContext *gb = &s->HEVClc->gb;

    if (size < 7)
        return AVERROR(EINVAL);
    size -= 7;

    country_code = get_bits(gb, 8);
    if (country_code == 0xFF) {
        skip_bits(gb, 8);
        size--;
    }

    skip_bits(gb, 8);
    skip_bits(gb, 8);

    user_identifier = get_bits_long(gb, 32);

    switch (user_identifier) {
        case MKBETAG('G', 'A', '9', '4'):
            return decode_registered_user_data_closed_caption(s, size);
        default:
            skip_bits_long(gb, size * 8);
            break;
    }
    return 0;
}

static int dca_parse_params(const uint8_t *buf, int buf_size, int *duration,
                            int *sample_rate, int *framesize)
{
    GetBitContext gb;
    uint8_t hdr[12 + AV_INPUT_BUFFER_PADDING_SIZE] = { 0 };
    int ret, sample_blocks, sr_code;

    if (buf_size < 12)
        return AVERROR_INVALIDDATA;

    if ((ret = avpriv_dca_convert_bitstream(buf, 12, hdr, 12)) < 0)
        return ret;

    init_get_bits(&gb, hdr, 96);

    skip_bits_long(&gb, 39);
    sample_blocks = get_bits(&gb, 7) + 1;
    if (sample_blocks < 8)
        return AVERROR_INVALIDDATA;
    *duration = 256 * (sample_blocks / 8);

    *framesize = get_bits(&gb, 14) + 1;
    if (*framesize < 95)
        return AVERROR_INVALIDDATA;

    skip_bits(&gb, 6);
    sr_code      = get_bits(&gb, 4);
    *sample_rate = avpriv_dca_sample_rates[sr_code];
    if (*sample_rate == 0)
        return AVERROR_INVALIDDATA;

    return 0;
}

static int latm_decode_audio_specific_config(struct LATMContext *latmctx,
        GetBitContext *gb, int asclen)
{
    AACContext *ac        = &latmctx->aac_ctx;
    AVCodecContext *avctx = ac->avctx;
    MPEG4AudioConfig m4ac = { 0 };
    int config_start_bit  = get_bits_count(gb);
    int sync_extension    = 0;
    int bits_consumed, esize;

    if (asclen) {
        sync_extension = 1;
        asclen         = FFMIN(asclen, get_bits_left(gb));
    } else
        asclen         = get_bits_left(gb);

    if (config_start_bit % 8) {
        avpriv_request_sample(latmctx->aac_ctx.avctx,
                              "Non-byte-aligned audio-specific config");
        return AVERROR_PATCHWELCOME;
    }
    if (asclen <= 0)
        return AVERROR_INVALIDDATA;
    bits_consumed = decode_audio_specific_config(NULL, avctx, &m4ac,
                    gb->buffer + (config_start_bit / 8),
                    asclen, sync_extension);

    if (bits_consumed < 0)
        return AVERROR_INVALIDDATA;

    if (!latmctx->initialized ||
            ac->oc[1].m4ac.sample_rate != m4ac.sample_rate ||
            ac->oc[1].m4ac.chan_config != m4ac.chan_config) {

        if(latmctx->initialized) {
            av_log(avctx, AV_LOG_INFO, "audio config changed\n");
        } else {
            av_log(avctx, AV_LOG_DEBUG, "initializing latmctx\n");
        }
        latmctx->initialized = 0;

        esize = (bits_consumed+7) / 8;

        if (avctx->extradata_size < esize) {
            av_free(avctx->extradata);
            avctx->extradata = av_malloc(esize + AV_INPUT_BUFFER_PADDING_SIZE);
            if (!avctx->extradata)
                return AVERROR(ENOMEM);
        }

        avctx->extradata_size = esize;
        memcpy(avctx->extradata, gb->buffer + (config_start_bit/8), esize);
        memset(avctx->extradata+esize, 0, AV_INPUT_BUFFER_PADDING_SIZE);
    }
    skip_bits_long(gb, bits_consumed);

    return bits_consumed;
}

/**
 * Skip mixing coefficients of a single mix out configuration (HD)
 */
static void dca_exss_skip_mix_coeffs(GetBitContext *gb, int channels, int out_ch)
{
    int i;

    for (i = 0; i < channels; i++) {
        int mix_map_mask = get_bits(gb, out_ch);
        int num_coeffs = av_popcount(mix_map_mask);
        skip_bits_long(gb, num_coeffs * 6);
    }
}

static void nelly_decode_block(NellyMoserDecodeContext *s,
                               const unsigned char block[NELLY_BLOCK_LEN],
                               float audio[NELLY_SAMPLES])
{
    int i,j;
    float buf[NELLY_FILL_LEN], pows[NELLY_FILL_LEN];
    float *aptr, *bptr, *pptr, val, pval;
    int bits[NELLY_BUF_LEN];
    unsigned char v;

    init_get_bits(&s->gb, block, NELLY_BLOCK_LEN * 8);

    bptr = buf;
    pptr = pows;
    val = ff_nelly_init_table[get_bits(&s->gb, 6)];
    for (i=0 ; i<NELLY_BANDS ; i++) {
        if (i > 0)
            val += ff_nelly_delta_table[get_bits(&s->gb, 5)];
        pval = -pow(2, val/2048) * s->scale_bias;
        for (j = 0; j < ff_nelly_band_sizes_table[i]; j++) {
            *bptr++ = val;
            *pptr++ = pval;
        }

    }

    ff_nelly_get_sample_bits(buf, bits);

    for (i = 0; i < 2; i++) {
        aptr = audio + i * NELLY_BUF_LEN;

        init_get_bits(&s->gb, block, NELLY_BLOCK_LEN * 8);
        skip_bits_long(&s->gb, NELLY_HEADER_BITS + i*NELLY_DETAIL_BITS);

        for (j = 0; j < NELLY_FILL_LEN; j++) {
            if (bits[j] <= 0) {
                aptr[j] = M_SQRT1_2*pows[j];
                if (av_lfg_get(&s->random_state) & 1)
                    aptr[j] *= -1.0;
            } else {
                v = get_bits(&s->gb, bits[j]);
                aptr[j] = ff_nelly_dequantization_table[(1<<bits[j])-1+v]*pows[j];
            }
        }
        memset(&aptr[NELLY_FILL_LEN], 0,
               (NELLY_BUF_LEN - NELLY_FILL_LEN) * sizeof(float));

        s->imdct_ctx.imdct_calc(&s->imdct_ctx, s->imdct_out, aptr);
        /* XXX: overlapping and windowing should be part of a more
           generic imdct function */
        s->dsp.vector_fmul_reverse(s->state, s->state, ff_sine_128, NELLY_BUF_LEN);
        s->dsp.vector_fmul_add(aptr, s->imdct_out, ff_sine_128, s->state, NELLY_BUF_LEN);
        memcpy(s->state, s->imdct_out + NELLY_BUF_LEN, sizeof(float)*NELLY_BUF_LEN);
    }
}

static int decode_nal_sei_suffix(GetBitContext *gb, void *logctx, HEVCSEI *s,
                                 int type, int size)
{
    switch (type) {
    case HEVC_SEI_TYPE_DECODED_PICTURE_HASH:
        return decode_nal_sei_decoded_picture_hash(&s->picture_hash, gb);
    default:
        av_log(logctx, AV_LOG_DEBUG, "Skipped SUFFIX SEI %d\n", type);
        skip_bits_long(gb, 8 * size);
        return 0;
    }
}

static int decode_nal_sei_suffix(HEVCContext *s, int type, int size)
{
    GetBitContext *gb = &s->HEVClc->gb;

    switch (type) {
    case SEI_TYPE_DECODED_PICTURE_HASH:
        return decode_nal_sei_decoded_picture_hash(s);
    default:
        av_log(s->avctx, AV_LOG_DEBUG, "Skipped SUFFIX SEI %d\n", type);
        skip_bits_long(gb, 8 * size);
        return 0;
    }
}

int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_size)
{
    GetBitContext gb;
    int specific_config_bitindex;

    init_get_bits(&gb, buf, buf_size*8);
    c->object_type = get_object_type(&gb);
    c->sample_rate = get_sample_rate(&gb, &c->sampling_index);
    c->chan_config = get_bits(&gb, 4);
    if (c->chan_config < FF_ARRAY_ELEMS(ff_mpeg4audio_channels))
        c->channels = ff_mpeg4audio_channels[c->chan_config];
    c->sbr = -1;
    if (c->object_type == AOT_SBR) {
        c->ext_object_type = c->object_type;
        c->sbr = 1;
        c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
        c->object_type = get_object_type(&gb);
        if (c->object_type == AOT_ER_BSAC)
            c->ext_chan_config = get_bits(&gb, 4);
    } else {
        c->ext_object_type = AOT_NULL;
        c->ext_sample_rate = 0;
    }
    specific_config_bitindex = get_bits_count(&gb);

    if (c->object_type == AOT_ALS) {
        skip_bits(&gb, 5);
        if (show_bits_long(&gb, 24) != MKBETAG('\0','A','L','S'))
            skip_bits_long(&gb, 24);

        specific_config_bitindex = get_bits_count(&gb);

        if (parse_config_ALS(&gb, c))
            return -1;
    }

    if (c->ext_object_type != AOT_SBR) {
        int bits_left = buf_size*8 - get_bits_count(&gb);
        for (; bits_left > 15; bits_left--) {
            if (show_bits(&gb, 11) == 0x2b7) { // sync extension
                get_bits(&gb, 11);
                c->ext_object_type = get_object_type(&gb);
                if (c->ext_object_type == AOT_SBR && (c->sbr = get_bits1(&gb)) == 1)
                    c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
                break;
            } else
                get_bits1(&gb); // skip 1 bit
        }
    }
    return specific_config_bitindex;
}

static int decode_frame(AVCodecContext *avctx, void *data,
                        int *got_frame_ptr, AVPacket *avpkt)
{
    BinkAudioContext *s = avctx->priv_data;
    AVFrame *frame      = data;
    GetBitContext *gb = &s->gb;
    int ret, consumed = 0;

    if (!get_bits_left(gb)) {
        uint8_t *buf;
        /* handle end-of-stream */
        if (!avpkt->size) {
            *got_frame_ptr = 0;
            return 0;
        }
        if (avpkt->size < 4) {
            av_log(avctx, AV_LOG_ERROR, "Packet is too small\n");
            return AVERROR_INVALIDDATA;
        }
        buf = av_realloc(s->packet_buffer, avpkt->size + FF_INPUT_BUFFER_PADDING_SIZE);
        if (!buf)
            return AVERROR(ENOMEM);
        s->packet_buffer = buf;
        memcpy(s->packet_buffer, avpkt->data, avpkt->size);
        init_get_bits(gb, s->packet_buffer, avpkt->size * 8);
        consumed = avpkt->size;

        /* skip reported size */
        skip_bits_long(gb, 32);
    }

    /* get output buffer */
    frame->nb_samples = s->frame_len;
    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0) {
        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return ret;
    }

    if (decode_block(s, (float **)frame->extended_data,
                     avctx->codec->id == AV_CODEC_ID_BINKAUDIO_DCT)) {
        av_log(avctx, AV_LOG_ERROR, "Incomplete packet\n");
        return AVERROR_INVALIDDATA;
    }
    get_bits_align32(gb);

    frame->nb_samples = s->block_size / avctx->channels;
    *got_frame_ptr    = 1;

    return consumed;
}