| Message ID | 20230314032557.945590-1-gwymor@tilde.club |
|---|---|
| State | New |
| Headers | show |
| Series | [FFmpeg-devel,v2] avformat/matroska: Write WebVTT subtitles according to MKV specs | expand |
| Context | Check | Description |
|---|---|---|
| yinshiyou/make_loongarch64 | success | Make finished |
| yinshiyou/make_fate_loongarch64 | success | Make fate finished |
| andriy/make_x86 | success | Make finished |
| andriy/make_fate_x86 | success | Make fate finished |
Gwyneth Morgan: > When writing WebMs, FFmpeg muxes WebVTT subtitles with the D_WEBVTT/* > codec tags from the WebM specs [1]. However, it does the same when > muxing MKV files, and the Matroska specifications instead use > S_TEXT/WEBVTT tags for WebVTT subtitles [2], which FFmpeg currently > doesn't understand. Support reading MKVs using either tag, write regular > MKVs with S_TEXT/WEBVTT, and write WebMs with the D_WEBVTT/* tags we > already use. > > [1]: https://www.webmproject.org/docs/container/ > [2]: https://matroska.org/technical/codec_specs.html#s_textwebvtt > > Signed-off-by: Gwyneth Morgan <gwymor@tilde.club> > Fixes: https://trac.ffmpeg.org/ticket/5641 > --- > v2: Rebase as later changes in ffmpeg.git conflicted with this patch. > > libavformat/matroska.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/libavformat/matroska.c b/libavformat/matroska.c > index 79b2d09..d9e5ff9 100644 > --- a/libavformat/matroska.c > +++ b/libavformat/matroska.c > @@ -60,16 +60,12 @@ const CodecTags ff_mkv_codec_tags[]={ > {"A_VORBIS" , AV_CODEC_ID_VORBIS}, > {"A_WAVPACK4" , AV_CODEC_ID_WAVPACK}, > > - {"D_WEBVTT/SUBTITLES" , AV_CODEC_ID_WEBVTT}, > - {"D_WEBVTT/CAPTIONS" , AV_CODEC_ID_WEBVTT}, > - {"D_WEBVTT/DESCRIPTIONS", AV_CODEC_ID_WEBVTT}, > - {"D_WEBVTT/METADATA" , AV_CODEC_ID_WEBVTT}, > - > {"S_TEXT/UTF8" , AV_CODEC_ID_SUBRIP}, > {"S_TEXT/UTF8" , AV_CODEC_ID_TEXT}, > {"S_TEXT/ASCII" , AV_CODEC_ID_TEXT}, > {"S_TEXT/ASS" , AV_CODEC_ID_ASS}, > {"S_TEXT/SSA" , AV_CODEC_ID_ASS}, > + {"S_TEXT/WEBVTT" , AV_CODEC_ID_WEBVTT}, > {"S_ASS" , AV_CODEC_ID_ASS}, > {"S_SSA" , AV_CODEC_ID_ASS}, > {"S_VOBSUB" , AV_CODEC_ID_DVD_SUBTITLE}, > @@ -78,6 +74,11 @@ const CodecTags ff_mkv_codec_tags[]={ > {"S_HDMV/TEXTST" , AV_CODEC_ID_HDMV_TEXT_SUBTITLE}, > {"S_ARIBSUB" , AV_CODEC_ID_ARIB_CAPTION}, > > + {"D_WEBVTT/SUBTITLES" , AV_CODEC_ID_WEBVTT}, > + {"D_WEBVTT/CAPTIONS" , AV_CODEC_ID_WEBVTT}, > + {"D_WEBVTT/DESCRIPTIONS", AV_CODEC_ID_WEBVTT}, > + {"D_WEBVTT/METADATA" , AV_CODEC_ID_WEBVTT}, > + > {"V_AV1" , AV_CODEC_ID_AV1}, > {"V_AVS2" , AV_CODEC_ID_AVS2}, > {"V_AVS3" , AV_CODEC_ID_AVS3}, The reason we write it the way we do is that webvtt is muxed differently in Matroska than WebM. This needs to be fixed, too, before S_TEXT/WEBVTT can be used for Matroska. - Andreas
On 2023-03-14 04:37:17+0100, Andreas Rheinhardt wrote: > The reason we write it the way we do is that webvtt is muxed differently > in Matroska than WebM. This needs to be fixed, too, before S_TEXT/WEBVTT > can be used for Matroska. Ah, I see. I wasn't aware of the differences in muxing. Thanks for the info.
diff --git a/libavformat/matroska.c b/libavformat/matroska.c index 79b2d09..d9e5ff9 100644 --- a/libavformat/matroska.c +++ b/libavformat/matroska.c @@ -60,16 +60,12 @@ const CodecTags ff_mkv_codec_tags[]={ {"A_VORBIS" , AV_CODEC_ID_VORBIS}, {"A_WAVPACK4" , AV_CODEC_ID_WAVPACK}, - {"D_WEBVTT/SUBTITLES" , AV_CODEC_ID_WEBVTT}, - {"D_WEBVTT/CAPTIONS" , AV_CODEC_ID_WEBVTT}, - {"D_WEBVTT/DESCRIPTIONS", AV_CODEC_ID_WEBVTT}, - {"D_WEBVTT/METADATA" , AV_CODEC_ID_WEBVTT}, - {"S_TEXT/UTF8" , AV_CODEC_ID_SUBRIP}, {"S_TEXT/UTF8" , AV_CODEC_ID_TEXT}, {"S_TEXT/ASCII" , AV_CODEC_ID_TEXT}, {"S_TEXT/ASS" , AV_CODEC_ID_ASS}, {"S_TEXT/SSA" , AV_CODEC_ID_ASS}, + {"S_TEXT/WEBVTT" , AV_CODEC_ID_WEBVTT}, {"S_ASS" , AV_CODEC_ID_ASS}, {"S_SSA" , AV_CODEC_ID_ASS}, {"S_VOBSUB" , AV_CODEC_ID_DVD_SUBTITLE}, @@ -78,6 +74,11 @@ const CodecTags ff_mkv_codec_tags[]={ {"S_HDMV/TEXTST" , AV_CODEC_ID_HDMV_TEXT_SUBTITLE}, {"S_ARIBSUB" , AV_CODEC_ID_ARIB_CAPTION}, + {"D_WEBVTT/SUBTITLES" , AV_CODEC_ID_WEBVTT}, + {"D_WEBVTT/CAPTIONS" , AV_CODEC_ID_WEBVTT}, + {"D_WEBVTT/DESCRIPTIONS", AV_CODEC_ID_WEBVTT}, + {"D_WEBVTT/METADATA" , AV_CODEC_ID_WEBVTT}, + {"V_AV1" , AV_CODEC_ID_AV1}, {"V_AVS2" , AV_CODEC_ID_AVS2}, {"V_AVS3" , AV_CODEC_ID_AVS3},
When writing WebMs, FFmpeg muxes WebVTT subtitles with the D_WEBVTT/* codec tags from the WebM specs [1]. However, it does the same when muxing MKV files, and the Matroska specifications instead use S_TEXT/WEBVTT tags for WebVTT subtitles [2], which FFmpeg currently doesn't understand. Support reading MKVs using either tag, write regular MKVs with S_TEXT/WEBVTT, and write WebMs with the D_WEBVTT/* tags we already use. [1]: https://www.webmproject.org/docs/container/ [2]: https://matroska.org/technical/codec_specs.html#s_textwebvtt Signed-off-by: Gwyneth Morgan <gwymor@tilde.club> Fixes: https://trac.ffmpeg.org/ticket/5641 --- v2: Rebase as later changes in ffmpeg.git conflicted with this patch. libavformat/matroska.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)