Function parse_coding_header

libavcodec/dca_core.c:154–348

5.3.2 - Primary audio coding header

// 5.3.2 - Primary audio coding header
static int parse_coding_header(DCACoreDecoder *s, enum HeaderType header, int xch_base)
{
    int n, ch, nchannels, header_size = 0, header_pos = get_bits_count(&s->gb);
    unsigned int mask, index;

    if (get_bits_left(&s->gb) < 0)
        return AVERROR_INVALIDDATA;

    switch (header) {
    case HEADER_CORE:
        // Number of subframes
        s->nsubframes = get_bits(&s->gb, 4) + 1;

        // Number of primary audio channels
        s->nchannels = get_bits(&s->gb, 3) + 1;
        if (s->nchannels != ff_dca_channels[s->audio_mode]) {
            av_log(s->avctx, AV_LOG_ERROR, "Invalid number of primary audio channels (%d) for audio channel arrangement (%d)\n", s->nchannels, s->audio_mode);
            return AVERROR_INVALIDDATA;
        }
        av_assert1(s->nchannels <= DCA_CHANNELS - 2);

        s->ch_mask = audio_mode_ch_mask[s->audio_mode];

        // Add LFE channel if present
        if (s->lfe_present)
            s->ch_mask |= DCA_SPEAKER_MASK_LFE1;
        break;

    case HEADER_XCH:
        s->nchannels = ff_dca_channels[s->audio_mode] + 1;
        av_assert1(s->nchannels <= DCA_CHANNELS - 1);
        s->ch_mask |= DCA_SPEAKER_MASK_Cs;
        break;

    case HEADER_XXCH:
        // Channel set header length
        header_size = get_bits(&s->gb, 7) + 1;

        // Check CRC
        if (s->xxch_crc_present
            && ff_dca_check_crc(s->avctx, &s->gb, header_pos, header_pos + header_size * 8)) {
            av_log(s->avctx, AV_LOG_ERROR, "Invalid XXCH channel set header checksum\n");
            return AVERROR_INVALIDDATA;
        }

        // Number of channels in a channel set
        nchannels = get_bits(&s->gb, 3) + 1;
        if (nchannels > DCA_XXCH_CHANNELS_MAX) {
            avpriv_request_sample(s->avctx, "%d XXCH channels", nchannels);
            return AVERROR_PATCHWELCOME;
        }
        s->nchannels = ff_dca_channels[s->audio_mode] + nchannels;
        av_assert1(s->nchannels <= DCA_CHANNELS);

        // Loudspeaker layout mask
        mask = get_bits_long(&s->gb, s->xxch_mask_nbits - DCA_SPEAKER_Cs);
        s->xxch_spkr_mask = mask << DCA_SPEAKER_Cs;