H.264: disable 2tap qpel with CODEC_FLAG2_FAST and >8-bit

2tap qpel isn't implemented yet for high bit depth, so it just breaks decoding.

libavcodec/h264.c

@@ -2485,7 +2485,8 @@ static int decode_slice_header(H264Context *h, H264Context *h0){
 
     s->dropable= h->nal_ref_idc == 0;
 
-    if((s->avctx->flags2 & CODEC_FLAG2_FAST) && !h->nal_ref_idc){
+    /* FIXME: 2tap qpel isn't implemented for high bit depth. */
+    if((s->avctx->flags2 & CODEC_FLAG2_FAST) && !h->nal_ref_idc && !h->pixel_shift){
         s->me.qpel_put= s->dsp.put_2tap_qpel_pixels_tab;
         s->me.qpel_avg= s->dsp.avg_2tap_qpel_pixels_tab;
     }else{