Half user provided time_base once during the first frame when there is no

timebase stored in the h264 stream.
This should fix fate. (ffmpeg.c used pict_repeat with its default 1/25 timebase)

Originally committed as revision 17622 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264.c

@@ -3768,6 +3768,9 @@ static int decode_slice_header(H264Context *h, H264Context *h0){
                 s->avctx->time_base.den *= 2;
             av_reduce(&s->avctx->time_base.num, &s->avctx->time_base.den,
                       s->avctx->time_base.num, s->avctx->time_base.den, 1<<30);
+        }else if(!h->sps.time_scale && !s->avctx->frame_number){
+            s->avctx->time_base.den *=2;
+            h->sps.time_scale= s->avctx->time_base.den;
         }
     }