dv-demux: dont mess with codec values

Fixes part of Ticket1369

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

libavformat/dv.c

@@ -273,9 +273,6 @@ static int dv_extract_video_info(DVDemuxContext *c, uint8_t* frame)
         avpriv_set_pts_info(c->vst, 64, c->sys->time_base.num,
                         c->sys->time_base.den);
         avctx->time_base= c->sys->time_base;
-        if (!avctx->width)
-            avcodec_set_dimensions(avctx, c->sys->width, c->sys->height);
-        avctx->pix_fmt = c->sys->pix_fmt;
 
         /* finding out SAR is a little bit messy */
         vsc_pack = dv_extract_pack(frame, dv_video_control);