Adapted from
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=44511b17cbbb524602c91a198e7314fa57a7062a
diff -Naurp libavcodec/rv34.c libavcodec/rv34.c.mikson
--- libavcodec/rv34.c   2009-03-22 19:19:21.000000000 +0000
+++ libavcodec/rv34.c.mikson    2011-06-23 07:43:27.837243045 +0000
@@ -1247,8 +1247,8 @@ static int rv34_decode_slice(RV34DecCont
         if(s->width != r->si.width || s->height != r->si.height){
             av_log(s->avctx, AV_LOG_DEBUG, "Changing dimensions to %dx%d\n", r->si.width,r->si.height);
             MPV_common_end(s);
-            s->width  = r->si.width;
-            s->height = r->si.height;
+            s->width  = s->avctx->width  = r->si.width;
+            s->height = s->avctx->height = r->si.height;
             if(MPV_common_init(s) < 0)
                 return -1;
             r->intra_types_hist = av_realloc(r->intra_types_hist, s->b4_stride * 4 * 2 * sizeof(*r->intra_types_hist));