[FFmpeg-cvslog] avformat/matroskaenc: Don't write empty language

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at gmail.com> | Tue Feb 16 15:53:25 2021 +0100| [3ac5530244a87612475d420e118e832efaa50478] | committer: Andreas Rheinhardt

avformat/matroskaenc: Don't write empty language

According to the new EBML specifications, a string element of length
zero would be read as the default value by a compliant parser.

Reviewed-by: Ridley Combs <rcombs at rcombs.me>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=3ac5530244a87612475d420e118e832efaa50478
---

 libavformat/matroskaenc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 233c472b8f..6c8c7130c0 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -1147,7 +1147,7 @@ static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,
         put_ebml_string(pb, MATROSKA_ID_TRACKNAME, tag->value);
     tag = av_dict_get(st->metadata, "language", NULL, 0);
     put_ebml_string(pb, MATROSKA_ID_TRACKLANGUAGE,
-                    tag && tag->value ? tag->value : "und");
+                    tag && tag->value[0] ? tag->value : "und");
 
     // The default value for TRACKFLAGDEFAULT is 1, so add element
     // if we need to clear it.