siff: set duration

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/siff.c

@@ -128,6 +128,8 @@ static int siff_parse_vbv1(AVFormatContext *s, SIFFContext *c, AVIOContext *pb)
     st->codec->width      = width;
     st->codec->height     = height;
     st->codec->pix_fmt    = AV_PIX_FMT_PAL8;
+    st->nb_frames         =
+    st->duration          = c->frames;
     avpriv_set_pts_info(st, 16, 1, 12);
 
     c->cur_frame = 0;