lavf: don't abort if both encoder and muxer aspect ratios are not set

Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/mux.c

@@ -187,6 +187,10 @@ static int init_muxer(AVFormatContext *s, AVDictionary **options)
 
             if (av_cmp_q(st->sample_aspect_ratio,
                          codec->sample_aspect_ratio)) {
+                if (st->sample_aspect_ratio.num != 0 &&
+                    st->sample_aspect_ratio.den != 0 &&
+                    codec->sample_aspect_ratio.den != 0 &&
+                    codec->sample_aspect_ratio.den != 0) {
                     av_log(s, AV_LOG_ERROR, "Aspect ratio mismatch between muxer "
                             "(%d/%d) and encoder layer (%d/%d)\n",
                             st->sample_aspect_ratio.num, st->sample_aspect_ratio.den,
@@ -195,6 +199,7 @@ static int init_muxer(AVFormatContext *s, AVDictionary **options)
                     ret = AVERROR(EINVAL);
                     goto fail;
                 }
+            }
             break;
         }