Function decode_subframe

libavcodec/wmaprodec.c:1045–1260

*@brief Decode a single subframe (block). *@param s codec context *@return 0 on success, < 0 when decoding failed */

 *@return 0 on success, < 0 when decoding failed
 */
static int decode_subframe(WMAProDecodeCtx *s)
{
    int offset = s->samples_per_frame;
    int subframe_len = s->samples_per_frame;
    int i;
    int total_samples   = s->samples_per_frame * s->num_channels;
    int transmit_coeffs = 0;
    int cur_subwoofer_cutoff;

    s->subframe_offset = get_bits_count(&s->gb);

    /** reset channel context and find the next block offset and size
        == the next block of the channel with the smallest number of
        decoded samples
    */
    for (i = 0; i < s->num_channels; i++) {
        s->channel[i].grouped = 0;
        if (offset > s->channel[i].decoded_samples) {
            offset = s->channel[i].decoded_samples;
            subframe_len =
                s->channel[i].subframe_len[s->channel[i].cur_subframe];
        }
    }

    dprintf(s->avctx,
            "processing subframe with offset %i len %i\n", offset, subframe_len);

    /** get a list of all channels that contain the estimated block */
    s->channels_for_cur_subframe = 0;
    for (i = 0; i < s->num_channels; i++) {
        const int cur_subframe = s->channel[i].cur_subframe;
        /** substract already processed samples */
        total_samples -= s->channel[i].decoded_samples;

        /** and count if there are multiple subframes that match our profile */
        if (offset == s->channel[i].decoded_samples &&
            subframe_len == s->channel[i].subframe_len[cur_subframe]) {
            total_samples -= s->channel[i].subframe_len[cur_subframe];
            s->channel[i].decoded_samples +=
                s->channel[i].subframe_len[cur_subframe];
            s->channel_indexes_for_cur_subframe[s->channels_for_cur_subframe] = i;
            ++s->channels_for_cur_subframe;
        }
    }

    /** check if the frame will be complete after processing the
        estimated block */
    if (!total_samples)
        s->parsed_all_subframes = 1;


    dprintf(s->avctx, "subframe is part of %i channels\n",
            s->channels_for_cur_subframe);

    /** calculate number of scale factor bands and their offsets */
    s->table_idx         = av_log2(s->samples_per_frame/subframe_len);
    s->num_bands         = s->num_sfb[s->table_idx];
    s->cur_sfb_offsets   = s->sfb_offsets[s->table_idx];