ffmpeg can't detect the language tag of mkv files after editing with mkvpropedit

[random404]

If you change the language of some mkv files with mkvpropedit, ffmpeg fails to see the new language even after remuxing the file again or running mkclean on the files.

[mkver]

Does your file have a tag called "LANGUAGE"?

[random404]

confirmed by ​https://gitlab.com/mbunkus/mkvtoolnix/-/issues/2826

and yes, like i said, both mkvinfo and mediainfo can see the correct language...only ffmpeg and ffprobe think it's undefined

[Carl Eugen Hoyos]

Please provide the command line you tested together with the complete, uncut console output and an input sample to make this a valid ticket.

[mkver]

Related to #7549. In this ticket, a tag that is parsed later overwrites a part of the metadata that has already been set via non-tags (via the TrackEntry's Language element); in #7549, an edition tag called TITLE is treated as if it were a segment's title.

Given that Matroska tags are supposed to be upper-case, one could distinguish the two by using AV_DICT_MATCH_CASE in both the demuxer as well as the muxer. But FFmpeg doesn't exist for Matroska alone and I don't know whether this might break anything. Most other demuxers use the key "title" for the title; only the mv demuxer seems to be setting "TITLE". Any title from mv would then be mapped to a tag which doesn't seem intended. ​My patch based upon this furthermore needs to change ff_metadata_conv slightly. I don't think that this will break anything though.

[random404]

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[random404]

I just found that if you remove all tags with

mkvpropedit "input.mkv" --tags all:

then ffmpeg will the language tag

output of mkvinfo after doing that:

+ EBML head
|+ EBML version: 1
|+ EBML read version: 1
|+ Maximum EBML ID length: 4
|+ Maximum EBML size length: 8
|+ Document type: matroska
|+ Document type version: 2
|+ Document type read version: 2
+ Segment: size 87805255
|+ Seek head (subentries will be skipped)
|+ EBML void: size 162
|+ Segment information
| + Timestamp scale: 1000000
| + Multiplexing application: Lavf55.12.0
| + Writing application: HandBrake 0.10.0 2014112200
| + Segment UID: 0x11 0x8d 0xb7 0xef 0x37 0x19 0x02 0xb2 0x7d 0x40 0x5a 0xbc 0x76 0xb8 0x71 0x47
| + Duration: 00:10:45.579000000
|+ Tracks
| + Track
|  + Track number: 1 (track ID for mkvmerge & mkvextract: 0)
|  + Track UID: 1
|  + Lacing flag: 0
|  + Language: und
|  + Codec ID: V_MPEG4/ISO/AVC
|  + Track type: video
|  + Default duration: 00:00:00.033366666 (29.970 frames/fields per second for a video track)
|  + Video track
|   + Pixel width: 1280
|   + Pixel height: 720
|   + Display width: 1280
|   + Display height: 720
|   + Display unit: 3 (aspect ratio)
|  + Codec's private data: size 43 (H.264 profile: Main @L4.0)
| + Track
|  + Track number: 2 (track ID for mkvmerge & mkvextract: 1)
|  + Track UID: 2
|  + Lacing flag: 0
|  + Name: Stereo
|  + Language: por
|  + Codec ID: A_AAC
|  + Track type: audio
|  + Audio track
|   + Channels: 2
|   + Sampling frequency: 44100
|  + Codec's private data: size 5
|+ EBML void: size 108
|+ Cluster