Function decode_channel_transform

libavcodec/wmaprodec.c:652–757

*@brief Decode channel transformation parameters *@param s codec context *@return 0 in case of success, < 0 in case of bitstream errors */

 *@return 0 in case of success, < 0 in case of bitstream errors
 */
static int decode_channel_transform(WMAProDecodeCtx* s)
{
    int i;
    /* should never consume more than 1921 bits for the 8 channel case
     * 1 + MAX_CHANNELS * (MAX_CHANNELS + 2 + 3 * MAX_CHANNELS * MAX_CHANNELS
     * + MAX_CHANNELS + MAX_BANDS + 1)
     */

    /** in the one channel case channel transforms are pointless */
    s->num_chgroups = 0;
    if (s->num_channels > 1) {
        int remaining_channels = s->channels_for_cur_subframe;

        if (get_bits1(&s->gb)) {
            av_log_ask_for_sample(s->avctx,
                                  "unsupported channel transform bit\n");
            return AVERROR_INVALIDDATA;
        }

        for (s->num_chgroups = 0; remaining_channels &&
             s->num_chgroups < s->channels_for_cur_subframe; s->num_chgroups++) {
            WMAProChannelGrp* chgroup = &s->chgroup[s->num_chgroups];
            float** channel_data = chgroup->channel_data;
            chgroup->num_channels = 0;
            chgroup->transform = 0;

            /** decode channel mask */
            if (remaining_channels > 2) {
                for (i = 0; i < s->channels_for_cur_subframe; i++) {
                    int channel_idx = s->channel_indexes_for_cur_subframe[i];
                    if (!s->channel[channel_idx].grouped
                        && get_bits1(&s->gb)) {
                        ++chgroup->num_channels;
                        s->channel[channel_idx].grouped = 1;
                        *channel_data++ = s->channel[channel_idx].coeffs;
                    }
                }
            } else {
                chgroup->num_channels = remaining_channels;
                for (i = 0; i < s->channels_for_cur_subframe; i++) {
                    int channel_idx = s->channel_indexes_for_cur_subframe[i];
                    if (!s->channel[channel_idx].grouped)
                        *channel_data++ = s->channel[channel_idx].coeffs;
                    s->channel[channel_idx].grouped = 1;
                }
            }

            /** decode transform type */
            if (chgroup->num_channels == 2) {
                if (get_bits1(&s->gb)) {
                    if (get_bits1(&s->gb)) {
                        av_log_ask_for_sample(s->avctx,
                                              "unsupported channel transform type\n");
                    }
                } else {
                    chgroup->transform = 1;
                    if (s->num_channels == 2) {
                        chgroup->decorrelation_matrix[0] =  1.0;