mpeg4videoenc: check w,h to be within the supported range.

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

libavcodec/mpeg4videoenc.c

@@ -1234,6 +1234,11 @@ static av_cold int encode_init(AVCodecContext *avctx)
     int ret;
     static int done = 0;
 
+    if (avctx->width >= (1<<13) || avctx->height >= (1<<13)) {
+        av_log(avctx, AV_LOG_ERROR, "dimensions too large for MPEG-4\n");
+        return AVERROR(EINVAL);
+    }
+
     if((ret=ff_MPV_encode_init(avctx)) < 0)
         return ret;