avformat_write_header(): detail error message

Give the exact aspect ratios when there is a mismatch between encoder
and muxer.
Signed-off-by: Anton Khirnov <anton@khirnov.net>

libavformat/utils.c

@@ -2782,7 +2782,11 @@ int avformat_write_header(AVFormatContext *s, AVDictionary **options)
                 goto fail;
             }
             if(av_cmp_q(st->sample_aspect_ratio, st->codec->sample_aspect_ratio)){
-                av_log(s, AV_LOG_ERROR, "Aspect ratio mismatch between encoder and muxer layer\n");
+                av_log(s, AV_LOG_ERROR, "Aspect ratio mismatch between encoder "
+                       "(%d/%d) and muxer layer (%d/%d)\n",
+                       st->sample_aspect_ratio.num, st->sample_aspect_ratio.den,
+                       st->codec->sample_aspect_ratio.num,
+                       st->codec->sample_aspect_ratio.den);
                 ret = AVERROR(EINVAL);
                 goto fail;
             }