avdevice/dshow: Fix frame rate

Fixes: Ticket5526

Tested-by: kgp700
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavdevice/dshow.c

@@ -953,6 +953,7 @@ dshow_add_device(AVFormatContext *avctx,
         }
 
         st->avg_frame_rate = av_inv_q(time_base);
+        st->r_frame_rate = av_inv_q(time_base);
 
         par->codec_type = AVMEDIA_TYPE_VIDEO;
         par->width      = bih->biWidth;