Consider slice_beta_offet in qp_thresh.

Originally committed as revision 21244 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264.c

@@ -2110,7 +2110,7 @@ static int decode_slice_header(H264Context *h, H264Context *h0){
                 return 1; // deblocking switched inside frame
         }
     }
-    h->qp_thresh= 15 - h->slice_alpha_c0_offset - FFMAX3(0, h->pps.chroma_qp_index_offset[0], h->pps.chroma_qp_index_offset[1]);
+    h->qp_thresh= 15 - FFMIN(h->slice_alpha_c0_offset, h->slice_beta_offset) - FFMAX3(0, h->pps.chroma_qp_index_offset[0], h->pps.chroma_qp_index_offset[1]);
 
 #if 0 //FMO
     if( h->pps.num_slice_groups > 1  && h->pps.mb_slice_group_map_type >= 3 && h->pps.mb_slice_group_map_type <= 5)