Replace assert in ff_xvmc_field_end() by av_log call at level AV_LOG_ERROR.

Originally committed as revision 17308 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegvideo_xvmc.c

@@ -290,13 +290,14 @@ void ff_xvmc_decode_mb(MpegEncContext *s)
     }
     render->filled_mv_blocks_num++;
 
-    assert(render->filled_mv_blocks_num     <= render->total_number_of_mv_blocks);
     assert(render->next_free_data_block_num <= render->total_number_of_data_blocks);
-    /* The above conditions should not be able to fail as long as this function
+    /* The above condition should not be able to fail as long as this function
      * is used and the following 'if ()' automatically calls a callback to free
      * blocks. */
 
 
     if (render->filled_mv_blocks_num >= render->total_number_of_mv_blocks)
         ff_draw_horiz_band(s, 0, 0);
+    else
+        av_log(s->avctx, AV_LOG_ERROR, "Not all blocks have been processed.\n");
 }