b frames & slices bugfix

Originally committed as revision 377 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h263dec.c

@@ -220,9 +220,15 @@ static int h263_decode_frame(AVCodecContext *avctx,
             if (h > 16)
                 h = 16;
             offset = y * s->linesize;
-            src_ptr[0] = s->current_picture[0] + offset;
+            if(s->pict_type==B_TYPE || (!s->has_b_frames)){
-            src_ptr[1] = s->current_picture[1] + (offset >> 2);
+                src_ptr[0] = s->current_picture[0] + offset;
-            src_ptr[2] = s->current_picture[2] + (offset >> 2);
+                src_ptr[1] = s->current_picture[1] + (offset >> 2);
+                src_ptr[2] = s->current_picture[2] + (offset >> 2);
+            } else {
+                src_ptr[0] = s->last_picture[0] + offset;
+                src_ptr[1] = s->last_picture[1] + (offset >> 2);
+                src_ptr[2] = s->last_picture[2] + (offset >> 2);
+            }
             avctx->draw_horiz_band(avctx, src_ptr, s->linesize,
                                    y, s->width, h);
         }