Anton Khirnov:
> Quoting Andreas Rheinhardt (2021-02-22 05:05:29)
>> Andreas Rheinhardt:
>>> Needs a CountedElement in order to distinguish the case of the element
>>> not being present and the element being present with a value of zero.
>>>
>>> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
>>> ---
>>> libavformat/matroska.h | 1 +
>>> libavformat/matroskadec.c | 7 ++++++-
>>> 2 files changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/libavformat/matroska.h b/libavformat/matroska.h
>>> index 191c4f6149..8ab87eff20 100644
>>> --- a/libavformat/matroska.h
>>> +++ b/libavformat/matroska.h
>>> @@ -100,6 +100,7 @@
>>> #define MATROSKA_ID_TRACKFLAGDEFAULT 0x88
>>> #define MATROSKA_ID_TRACKFLAGFORCED 0x55AA
>>> #define MATROSKA_ID_TRACKFLAGLACING 0x9C
>>> +#define MATROSKA_ID_TRACKFLAGORIGINAL 0x55AE
>>> #define MATROSKA_ID_TRACKMINCACHE 0x6DE7
>>> #define MATROSKA_ID_TRACKMAXCACHE 0x6DF8
>>> #define MATROSKA_ID_TRACKDEFAULTDURATION 0x23E383
>>> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
>>> index fa266fcaec..f15bf8f9d2 100644
>>> --- a/libavformat/matroskadec.c
>>> +++ b/libavformat/matroskadec.c
>>> @@ -251,6 +251,7 @@ typedef struct MatroskaTrack {
>>> uint64_t flag_default;
>>> uint64_t flag_forced;
>>> uint64_t flag_comment;
>>> + CountedElement flag_original;
>>> uint64_t seek_preroll;
>>> MatroskaTrackVideo video;
>>> MatroskaTrackAudio audio;
>>> @@ -410,7 +411,7 @@ typedef struct MatroskaDemuxContext {
>>> // incomplete type (6.7.2 in C90, 6.9.2 in C99).
>>> // Removing the sizes breaks MSVC.
>>> static EbmlSyntax ebml_syntax[3], matroska_segment[9],
>>> matroska_track_video_color[15], matroska_track_video[19],
>>> - matroska_track[28], matroska_track_encoding[6],
>>> matroska_track_encodings[2],
>>> + matroska_track[29], matroska_track_encoding[6],
>>> matroska_track_encodings[2],
>>> matroska_track_combine_planes[2],
>>> matroska_track_operation[2], matroska_tracks[2],
>>> matroska_attachments[2], matroska_chapter_entry[9],
>>> matroska_chapter[6], matroska_chapters[2],
>>> matroska_index_entry[3], matroska_index[2],
>>> matroska_tag[3], matroska_tags[2], matroska_seekhead[2],
>>> @@ -575,6 +576,7 @@ static EbmlSyntax matroska_track[] = {
>>> { MATROSKA_ID_TRACKFLAGCOMMENTARY, EBML_UINT, 0, 0,
>>> offsetof(MatroskaTrack, flag_comment), { .u = 0 } },
>>> { MATROSKA_ID_TRACKFLAGDEFAULT, EBML_UINT, 0, 0,
>>> offsetof(MatroskaTrack, flag_default), { .u = 1 } },
>>> { MATROSKA_ID_TRACKFLAGFORCED, EBML_UINT, 0, 0,
>>> offsetof(MatroskaTrack, flag_forced), { .u = 0 } },
>>> + { MATROSKA_ID_TRACKFLAGORIGINAL, EBML_UINT, 1, 0,
>>> offsetof(MatroskaTrack, flag_original), {.u = 0 } },
>>> { MATROSKA_ID_TRACKVIDEO, EBML_NEST, 0, 0,
>>> offsetof(MatroskaTrack, video), { .n = matroska_track_video } },
>>> { MATROSKA_ID_TRACKAUDIO, EBML_NEST, 0, 0,
>>> offsetof(MatroskaTrack, audio), { .n = matroska_track_audio } },
>>> { MATROSKA_ID_TRACKOPERATION, EBML_NEST, 0, 0,
>>> offsetof(MatroskaTrack, operation), { .n = matroska_track_operation } },
>>> @@ -2746,6 +2748,9 @@ static int matroska_parse_tracks(AVFormatContext *s)
>>> st->disposition |= AV_DISPOSITION_FORCED;
>>> if (track->flag_comment)
>>> st->disposition |= AV_DISPOSITION_COMMENT;
>>> + if (track->flag_original.count > 0)
>>> + st->disposition |= track->flag_original.el.u ?
>>> AV_DISPOSITION_ORIGINAL
>>> + :
>>> AV_DISPOSITION_DUB;
>>>
>>> if (!st->codecpar->extradata) {
>>> if (extradata) {
>>>
>> Ridley Combs reviewed this set via IRC and approved it with one
>> exception: It makes no sense to use AV_DISPOSITION_DUB for something
>> else than an audio track, so if FlagOriginal is set to zero (meaning the
>> track is not in the content's original language), it should not be
>> exported at all. And the muxer should ignore AV_DISPOSITION_DUB for
>> non-audio-tracks. How do others think about this?
>
> AV_DISPOSITION_DUB is not documented, so you can interpret it pretty
> widely. One interpretation that I can think of is:
> - there are two audio tracks - let's say japanese original and english
> dub
> - there are also two english subtitle tracks:
> * one that translates everything, meant to be used with the original
> audio;
> * the other one translating just the text in the video (and possibly
> things that were meant to be subtitled in the original, like
> speech in Klingon), meant to be used with the english dub
>
> Then it can make sense to tag the second subtitle track with
> AV_DISPOSITION_DUB to indicate it is supposed to be used with the dubbed
> audio track.
>
That is also pretty much what I thought; furthermore, I'd really hate if
something was lost during a remuxing. I will therefore apply this as-is
tomorrow unless more comes up.
(I will leave the matroska-wtv-remux fate test out of this for reasons
explained here:
https://ffmpeg.org/pipermail/ffmpeg-devel/2021-February/276986.html)
- Andreas
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