Intialize the codec type to video.

Originally committed as revision 463 to svn://svn.ffmpeg.org/ffmpeg/trunk

libav/grab.c

@@ -221,6 +221,7 @@ static int grab_read_header(AVFormatContext *s1, AVFormatParameters *ap)
     s->fd = video_fd;
     s->frame_size = frame_size;
     
+    st->codec.codec_type = CODEC_TYPE_VIDEO;
     st->codec.codec_id = CODEC_ID_RAWVIDEO;
     st->codec.width = width;
     st->codec.height = height;