vp3: Allocate a dummy reference frame if we have no keyframe

Originally committed as revision 22360 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/vp3.c

@@ -1835,9 +1835,15 @@ static int vp3_decode_frame(AVCodecContext *avctx,
         }
     } else {
         if (!s->golden_frame.data[0]) {
-            av_log(s->avctx, AV_LOG_ERROR, "vp3: first frame not a keyframe\n");
+            av_log(s->avctx, AV_LOG_WARNING, "vp3: first frame not a keyframe\n");
+            s->golden_frame.reference = 3;
+            if (avctx->get_buffer(avctx, &s->golden_frame) < 0) {
+                av_log(s->avctx, AV_LOG_ERROR, "get_buffer() failed\n");
                 goto error;
             }
+            s->last_frame = s->golden_frame;
+            s->last_frame.type = FF_BUFFER_TYPE_COPY;
+        }
     }
 
     s->current_frame.qscale_table= s->qscale_table; //FIXME allocate individual tables per AVFrame