static int h261_decode_mb(H261Context *h, DCTELEM block[6][64]) { MpegEncContext * const s = &h->s; int i, cbp, xy, old_mtype; cbp = 63; // Read mba do{ h->mba_diff = get_vlc2(&s->gb, h261_mba_vlc.table, H261_MBA_VLC_BITS, 2)+1; } while( h->mba_diff == MAX_MBA + 1 ); // stuffing if ( h->mba_diff < 0 ) return -1; h->current_mba += h->mba_diff; if ( h->current_mba > MAX_MBA ) return -1; s->mb_x= ((h->gob_number-1) % 2) * 11 + ((h->current_mba-1) % 11); s->mb_y= ((h->gob_number-1) / 2) * 3 + ((h->current_mba-1) / 11); xy = s->mb_x + s->mb_y * s->mb_stride; ff_init_block_index(s); ff_update_block_index(s); s->dsp.clear_blocks(s->block[0]); // Read mtype old_mtype = h->mtype; h->mtype = get_vlc2(&s->gb, h261_mtype_vlc.table, H261_MTYPE_VLC_BITS, 2); h->mtype = h261_mtype_map[h->mtype]; if (IS_FIL (h->mtype)) h->loop_filter = 1; // Read mquant if ( IS_QUANT ( h->mtype ) ){ ff_set_qscale(s, get_bits(&s->gb, 5)); } s->mb_intra = IS_INTRA4x4(h->mtype); // Read mv if ( IS_16X16 ( h->mtype ) ){ // Motion vector data is included for all MC macroblocks. MVD is obtained from the macroblock vector by subtracting the // vector of the preceding macroblock. For this calculation the vector of the preceding macroblock is regarded as zero in the // following three situations: // 1) evaluating MVD for macroblocks 1, 12 and 23; // 2) evaluating MVD for macroblocks in which MBA does not represent a difference of 1; // 3) MTYPE of the previous macroblock was not MC. if ( ( h->current_mba == 1 ) || ( h->current_mba == 12 ) || ( h->current_mba == 23 ) || ( h->mba_diff != 1) || ( !IS_16X16 ( old_mtype ) )) { h->current_mv_x = 0; h->current_mv_y = 0; } h->current_mv_x= decode_mv_component(&s->gb, h->current_mv_x); h->current_mv_y= decode_mv_component(&s->gb, h->current_mv_y); } // Read cbp if ( HAS_CBP( h->mtype ) ){ cbp = get_vlc2(&s->gb, h261_cbp_vlc.table, H261_CBP_VLC_BITS, 2) + 1; } if(s->mb_intra){ s->current_picture.mb_type[xy]= MB_TYPE_INTRA; goto intra; } //set motion vectors s->mv_dir = MV_DIR_FORWARD; s->mv_type = MV_TYPE_16X16; s->current_picture.mb_type[xy]= MB_TYPE_16x16 | MB_TYPE_L0; if(IS_16X16 ( h->mtype )){ s->mv[0][0][0] = h->current_mv_x * 2;//gets divided by 2 in motion compensation s->mv[0][0][1] = h->current_mv_y * 2; } else{ h->current_mv_x = s->mv[0][0][0] = 0; h->current_mv_x = s->mv[0][0][1] = 0; } intra: /* decode each block */ if(s->mb_intra || HAS_CBP(h->mtype)){ for (i = 0; i < 6; i++) { if (h261_decode_block(h, block[i], i, cbp&32) < 0){ return -1; } cbp+=cbp; } } /* per-MB end of slice check */ { int v= show_bits(&s->gb, 15); if(get_bits_count(&s->gb) + 15 > s->gb.size_in_bits){ v>>= get_bits_count(&s->gb) + 15 - s->gb.size_in_bits; } if(v==0){ return SLICE_END; } } return SLICE_OK; }