Function mpeg_decode_mb

libavcodec/mpeg12.c:207–579

#define MT_DMV   3

static int mpeg_decode_mb(MpegEncContext *s,
                          DCTELEM block[12][64])
{
    int i, j, k, cbp, val, mb_type, motion_type;
    const int mb_block_count = 4 + (1<< s->chroma_format);

    dprintf(s->avctx, "decode_mb: x=%d y=%d\n", s->mb_x, s->mb_y);

    assert(s->mb_skipped==0);

    if (s->mb_skip_run-- != 0) {
        if (s->pict_type == FF_P_TYPE) {
            s->mb_skipped = 1;
            s->current_picture.mb_type[ s->mb_x + s->mb_y*s->mb_stride ]= MB_TYPE_SKIP | MB_TYPE_L0 | MB_TYPE_16x16;
        } else {
            int mb_type;

            if(s->mb_x)
                mb_type= s->current_picture.mb_type[ s->mb_x + s->mb_y*s->mb_stride - 1];
            else
                mb_type= s->current_picture.mb_type[ s->mb_width + (s->mb_y-1)*s->mb_stride - 1]; // FIXME not sure if this is allowed in MPEG at all
            if(IS_INTRA(mb_type))
                return -1;

            s->current_picture.mb_type[ s->mb_x + s->mb_y*s->mb_stride ]=
                mb_type | MB_TYPE_SKIP;
//            assert(s->current_picture.mb_type[ s->mb_x + s->mb_y*s->mb_stride - 1]&(MB_TYPE_16x16|MB_TYPE_16x8));

            if((s->mv[0][0][0]|s->mv[0][0][1]|s->mv[1][0][0]|s->mv[1][0][1])==0)
                s->mb_skipped = 1;
        }

        return 0;
    }

    switch(s->pict_type) {
    default:
    case FF_I_TYPE:
        if (get_bits1(&s->gb) == 0) {
            if (get_bits1(&s->gb) == 0){
                av_log(s->avctx, AV_LOG_ERROR, "invalid mb type in I Frame at %d %d\n", s->mb_x, s->mb_y);
                return -1;
            }
            mb_type = MB_TYPE_QUANT | MB_TYPE_INTRA;
        } else {
            mb_type = MB_TYPE_INTRA;
        }
        break;
    case FF_P_TYPE:
        mb_type = get_vlc2(&s->gb, mb_ptype_vlc.table, MB_PTYPE_VLC_BITS, 1);
        if (mb_type < 0){
            av_log(s->avctx, AV_LOG_ERROR, "invalid mb type in P Frame at %d %d\n", s->mb_x, s->mb_y);
            return -1;
        }
        mb_type = ptype2mb_type[ mb_type ];
        break;
    case FF_B_TYPE:
        mb_type = get_vlc2(&s->gb, mb_btype_vlc.table, MB_BTYPE_VLC_BITS, 1);