Try to fix has_b_frame calculation for open gop files.

Fixes issue1523

Originally committed as revision 20504 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264.c

@@ -7795,7 +7795,7 @@ static int decode_frame(AVCodecContext *avctx,
     if(!(s->flags2 & CODEC_FLAG2_CHUNKS) || (s->mb_y >= s->mb_height && s->mb_height)){
         Picture *out = s->current_picture_ptr;
         Picture *cur = s->current_picture_ptr;
-        int i, pics, cross_idr, out_of_order, out_idx;
+        int i, pics, out_of_order, out_idx;
 
         field_end(h);
 
@@ -7899,15 +7899,15 @@ static int decode_frame(AVCodecContext *avctx,
                     out = h->delayed_pic[i];
                     out_idx = i;
                 }
-            cross_idr = !!h->delayed_pic[i] || h->delayed_pic[0]->key_frame || h->delayed_pic[0]->mmco_reset;
-
-            out_of_order = !cross_idr && out->poc < h->outputed_poc;
+            if(s->avctx->has_b_frames == 0 && (h->delayed_pic[0]->key_frame || h->delayed_pic[0]->mmco_reset))
+                h->outputed_poc= INT_MIN;
+            out_of_order = out->poc < h->outputed_poc;
 
             if(h->sps.bitstream_restriction_flag && s->avctx->has_b_frames >= h->sps.num_reorder_frames)
                 { }
             else if((out_of_order && pics-1 == s->avctx->has_b_frames && s->avctx->has_b_frames < MAX_DELAYED_PIC_COUNT)
                || (s->low_delay &&
-                ((!cross_idr && out->poc > h->outputed_poc + 2)
+                ((h->outputed_poc != INT_MIN && out->poc > h->outputed_poc + 2)
                  || cur->pict_type == FF_B_TYPE)))
             {
                 s->low_delay = 0;
@@ -7922,6 +7922,9 @@ static int decode_frame(AVCodecContext *avctx,
             if(!out_of_order && pics > s->avctx->has_b_frames){
                 *data_size = sizeof(AVFrame);
 
+                if(out_idx==0 && h->delayed_pic[0] && (h->delayed_pic[0]->key_frame || h->delayed_pic[0]->mmco_reset)) {
+                    h->outputed_poc = INT_MIN;
+                } else
                 h->outputed_poc = out->poc;
                 *pict= *(AVFrame*)out;
             }else{