Function build_matrix

libswresample/rematrix.c:134–345

}

static void build_matrix(const AVChannelLayout *in_ch_layout, const AVChannelLayout *out_ch_layout,
                         double center_mix_level, double surround_mix_level,
                         double lfe_mix_level, double maxval, double rematrix_volume, double *matrix_param,
                         ptrdiff_t stride, enum AVMatrixEncoding matrix_encoding)
{
    double matrix[NUM_NAMED_CHANNELS][NUM_NAMED_CHANNELS]={{0}};
    uint64_t unaccounted =  av_channel_layout_subset(in_ch_layout,  UINT64_MAX) &
                           ~av_channel_layout_subset(out_ch_layout, UINT64_MAX);
    double maxcoef=0;
    int i, j;

    for(i=0; i<FF_ARRAY_ELEMS(matrix); i++){
        if(   av_channel_layout_index_from_channel(in_ch_layout, i) >= 0
           && av_channel_layout_index_from_channel(out_ch_layout, i) >= 0)
            matrix[i][i]= 1.0;
    }

//FIXME implement dolby surround
//FIXME implement full ac3

    if(unaccounted & AV_CH_FRONT_CENTER){
        if (av_channel_layout_subset(out_ch_layout, AV_CH_LAYOUT_STEREO) == AV_CH_LAYOUT_STEREO) {
            if (av_channel_layout_subset(in_ch_layout, AV_CH_LAYOUT_STEREO)) {
                matrix[ FRONT_LEFT][FRONT_CENTER]+= center_mix_level;
                matrix[FRONT_RIGHT][FRONT_CENTER]+= center_mix_level;
            } else {
                matrix[ FRONT_LEFT][FRONT_CENTER]+= M_SQRT1_2;
                matrix[FRONT_RIGHT][FRONT_CENTER]+= M_SQRT1_2;
            }
        }else
            av_assert0(0);
    }
    if(unaccounted & AV_CH_LAYOUT_STEREO){
        if (av_channel_layout_index_from_channel(out_ch_layout, AV_CHAN_FRONT_CENTER) >= 0) {
            matrix[FRONT_CENTER][ FRONT_LEFT]+= M_SQRT1_2;
            matrix[FRONT_CENTER][FRONT_RIGHT]+= M_SQRT1_2;
            if (av_channel_layout_index_from_channel(in_ch_layout, AV_CHAN_FRONT_CENTER) >= 0)
                matrix[FRONT_CENTER][ FRONT_CENTER] = center_mix_level*sqrt(2);
        }else
            av_assert0(0);
    }

    if(unaccounted & AV_CH_BACK_CENTER){
        if (av_channel_layout_index_from_channel(out_ch_layout, AV_CHAN_BACK_LEFT) >= 0) {
            matrix[ BACK_LEFT][BACK_CENTER]+= M_SQRT1_2;
            matrix[BACK_RIGHT][BACK_CENTER]+= M_SQRT1_2;
        } else if (av_channel_layout_index_from_channel(out_ch_layout, AV_CHAN_SIDE_LEFT) >= 0) {
            matrix[ SIDE_LEFT][BACK_CENTER]+= M_SQRT1_2;
            matrix[SIDE_RIGHT][BACK_CENTER]+= M_SQRT1_2;
        } else if (av_channel_layout_index_from_channel(out_ch_layout, AV_CHAN_FRONT_LEFT) >= 0) {
            if (matrix_encoding == AV_MATRIX_ENCODING_DOLBY ||
                matrix_encoding == AV_MATRIX_ENCODING_DPLII) {
                if (unaccounted & (AV_CH_BACK_LEFT | AV_CH_SIDE_LEFT)) {
                    matrix[FRONT_LEFT ][BACK_CENTER] -= surround_mix_level * M_SQRT1_2;
                    matrix[FRONT_RIGHT][BACK_CENTER] += surround_mix_level * M_SQRT1_2;
                } else {
                    matrix[FRONT_LEFT ][BACK_CENTER] -= surround_mix_level;
                    matrix[FRONT_RIGHT][BACK_CENTER] += surround_mix_level;