use precalculated mb_pos where available

Originally committed as revision 16194 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/rv34.c

@@ -1148,13 +1148,13 @@ static int rv34_decode_macroblock(RV34DecContext *r, int8_t *intra_types)
 
     s->qscale = r->si.quant;
     cbp = cbp2 = rv34_decode_mb_header(r, intra_types);
-    r->cbp_luma  [s->mb_x + s->mb_y * s->mb_stride] = cbp;
-    r->cbp_chroma[s->mb_x + s->mb_y * s->mb_stride] = cbp >> 16;
+    r->cbp_luma  [mb_pos] = cbp;
+    r->cbp_chroma[mb_pos] = cbp >> 16;
     if(s->pict_type == FF_I_TYPE)
         r->deblock_coefs[mb_pos] = 0xFFFF;
     else
         r->deblock_coefs[mb_pos] = rv34_set_deblock_coef(r) | r->cbp_luma[mb_pos];
-    s->current_picture_ptr->qscale_table[s->mb_x + s->mb_y * s->mb_stride] = s->qscale;
+    s->current_picture_ptr->qscale_table[mb_pos] = s->qscale;
 
     if(cbp == -1)
         return -1;
@@ -1188,7 +1188,7 @@ static int rv34_decode_macroblock(RV34DecContext *r, int8_t *intra_types)
         rv34_dequant4x4(s->block[blknum] + blkoff, rv34_qscale_tab[rv34_chroma_quant[1][s->qscale]],rv34_qscale_tab[rv34_chroma_quant[0][s->qscale]]);
         rv34_inv_transform(s->block[blknum] + blkoff);
     }
-    if(IS_INTRA(s->current_picture_ptr->mb_type[s->mb_x + s->mb_y*s->mb_stride]))
+    if(IS_INTRA(s->current_picture_ptr->mb_type[mb_pos]))
         rv34_output_macroblock(r, intra_types, cbp2, r->is16);
     else
         rv34_apply_differences(r, cbp2);