SVQ3 : Set avctx->pix_fmt correctly during decoder initialisation.

Fixes issue 1591.

Originally committed as revision 20810 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/svq3.c

@@ -796,6 +796,7 @@ static av_cold int svq3_decode_init(AVCodecContext *avctx)
     s->flags2 = avctx->flags2;
     s->unrestricted_mv = 1;
     h->is_complex=1;
+    avctx->pix_fmt = avctx->codec->pix_fmts[0];
 
     if (!s->context_initialized) {
         s->width  = avctx->width;