h263enc: test that dimensions are a multiple of 4

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

libavcodec/mpegvideo_enc.c

@@ -487,6 +487,13 @@ av_cold int ff_MPV_encode_init(AVCodecContext *avctx)
         av_log(avctx, AV_LOG_ERROR, "H.263 does not support resolutions above 2048x1152\n");
         return -1;
     }
+    if ((s->codec_id == CODEC_ID_H263  ||
+         s->codec_id == CODEC_ID_H263P) &&
+        ((avctx->width &3) ||
+         (avctx->height&3) )) {
+        av_log(avctx, AV_LOG_ERROR, "w/h must be a multiple of 4\n");
+        return -1;
+    }
 
     if ((s->flags & (CODEC_FLAG_INTERLACED_DCT | CODEC_FLAG_INTERLACED_ME)) &&
         s->codec_id != CODEC_ID_MPEG4 && s->codec_id != CODEC_ID_MPEG2VIDEO) {