set pix_fmt in rv10 patch by (James Stembridge <jstembridge at users dot sourceforge dot net>)

Originally committed as revision 1909 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/rv10.c

@@ -388,6 +388,8 @@ static int rv10_decode_init(AVCodecContext *avctx)
         done = 1;
     }
     
+    avctx->pix_fmt = PIX_FMT_YUV420P;
+
     return 0;
 }