feat: store tracklist as tag comment on recording #13761

acolombier · 2024-10-13T19:27:41Z

Implemented for MP3 and Wave and tested with both.

ffprobe example with MP3

$ ffprobe ../2024-10-13_20h38m19s.mp3 
ffprobe [...]
   [...]
[mp3 @ 0x556661ba7b80] Skipping 339 bytes of junk at 813.
Input #0, mp3, from '/home/antoine/Music/Mixxx/Recordings/2024-10-13_20h38m19s.mp3':
  Metadata:
    encoder         : LAME 64bits version 3.100 (http://lame.sf.net)
    title           : Foo
    artist          : Bar
    album           : Baz
    comment         : 00:00:00: Twenty One Pilots - The Craving (single version)
                    : 00:00:09: Carnage - Psy Or Die
                    : 00:00:19: bbno$ - it boy
                    : 00:00:38: Armin van Buuren feat. Trevor Guthrie - This Is What It Feels Like
                    : 00:00:47: Armin van Buuren - Larger Than Life
                    : 00:01:06: Freestylers - Cracks - Flux Pavilion Remix
  Duration: 00:01:17.14, start: 0.023021, bitrate: 128 kb/s
  Stream #0:0: Audio: mp3, 48000 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : LAME3.100

Note on MP3

After a long day of learning MP3 spec, it would appears that our implementation was somewhat flawed. My understanding is that the Xing frame that contains various parameter about the MP3 frames is expect in the beginning of the file, however we currently overwrite the first frames with it, leading to data loss. Since a frame is < 100ms, this is not something you can easily hear.

Second point is, we currently only write IDv1 (automatically supported by lame) but this limits the comment to 30 bytes. In order to lift this limit (and reach the hard limit of 2**32), we need to write ID3v2, but those are expected as header (unlike ID3v1 which can be appended in the footer when flushing the file.

In an ideal world, we would want to shift the file content to fit the ID3 header + the Xing frame. Because this basically requires to tear down the whole EncoderCallback mecanism, this instead adds a static header of 10K, which will be filled with the header, leading to a hard limit for comment (limit which depends of the artist, title and album size, as well the Xing frame size.

Appreciate this is far from optimal, but hopefully we can find an acceptable trade-off

src/encoder/encoder.cpp

Swiftb0y · 2024-10-14T12:57:59Z

considering the complications and tradeoffs there are with writing large metadata, why not write this tracklist as a separate file like the cuesheet? Is there that much value to having it part of the file metadata?

acolombier · 2024-10-14T20:03:46Z

considering the complications and tradeoffs there are with writing large metadata, why not write this tracklist as a separate file like the cuesheet? Is there that much value to having it part of the file metadata?

Because that's not the feature 😃

We already support the ability to generate a cue file, but there was a requested feature to have the ability to store the track. I think that's a fair request as the cue file isn't embedded.
I sometime copy recording of set I have made on my phone, and having a way to check the tracklist as comment metadata would be a great value

Swiftb0y · 2024-10-14T20:07:20Z

fully agree, I just find it weird that its a different format from the cuesheet, so I figured these were two different features.

Holzhaus · 2024-10-14T20:36:38Z

Didn't check the code, but I was wondering: Is this only for MP3/ID3?

For FLAC I think there is the CUESHEET tag block which is specifically for this purpose and might have proper support by audio players.

Holzhaus · 2024-10-14T20:38:11Z

https://www.xiph.org/flac/format.html#metadata_block_cuesheet

acolombier · 2024-10-14T20:59:24Z

I was wondering: Is this only for MP3/ID3?

Yes - only for MP3/ID3 and Wave so far. Since the FLAC encoder inherits the Wave one, it would also support the COMMENT field to be filled up.

https://www.xiph.org/flac/format.html#metadata_block_cuesheet

Nice, I'm wondering how widely is this supported? It feels like some custom logic that could be added in the recordermanager to duplicate the sheets in the FLAC file before flushing. It sounds a bit hacky, but I don't think other format would support cuesheet within their tag's spec?

acolombier · 2025-02-23T02:38:52Z

(Edit: didn't work :( )
/softfix

daschuer

I can confirm it works for mp3, but unfortunately not for wav.

res/controllers/DummyDeviceDefaultScreen.qml

src/encoder/encoder.cpp

src/encoder/encoder.h

src/encoder/encoderfdkaac.h

src/encoder/encodermp3.cpp

daschuer · 2025-04-27T00:35:03Z

I have this is Mixxx. It remains after reloading form track and utf8 is used:

This is vlc player:

daschuer · 2025-04-27T01:48:09Z

https://mutagen-specs.readthedocs.io/en/latest/id3/id3v2.2.html#comments
In the header the encoding is 00 = latin1. Mixxx writes 03 = utf8.
Lame writes comments as Latin1:
https://github.com/intervigilium/liblame/blob/dd48f963e34c1ef0b831083e87a08097464ee3b0/jni/lame/id3tag.c#L601
So you proably need to use taglib to write unicode or hack something up with lame.

acolombier · 2025-04-27T17:04:53Z

Ah that makes sense! Now that you pointed this out, I just thought I could use TagLib instead of liblame. I have reworked it and it works great across the board (ffprobe, vlc, mixxx tested)

The only rough edge is the ellipsis/UTF8 truncating, but I believe this is edge case enough the ignore for now. In case we get complains, we can always focus on solving the root cause problem, which is a limitation in the encoder callback API, not allowing to prepend data.

daschuer

Oh just noticed I had a pending review.

src/encoder/encodermp3.cpp

daschuer · 2025-04-27T18:47:58Z

Mp3 looks good now. Wave encoding has still an issue.

Can we use taglib for all?

acolombier · 2025-04-27T18:53:34Z

Can we use taglib for all?

Yep, that sounds like a wise approach.

daschuer · 2025-04-27T18:54:15Z

The first recording after enable tracklist does not work.

Select WAV encoding
Disable tracklist
Restart Mixxx
Enable tracklist
Start recording
No tracklist is logged
Expexted result
Tracklist shall b e logged.

src/encoder/encodermp3.cpp

acolombier · 2025-04-27T23:44:56Z

I have pushed a rewrite of the wave encoder with TagLib. Sadly, the whole LIST frame doesn't get generated by TagLib, so I had to build the header dynamically. There is some edge cases that aren't handled (e.g int overflow) but I think is edge enough to be ignored.
Looking at the libsndfile, it sounds like utf8 is not officially supported, but ffprobe, VLC and Mixxx both now show it fine, so it's probably good enough.

I believe I also fixed the bug you had found.

daschuer

I can no longer make the feature work for wav.

src/encoder/encodermp3.cpp

…t-as-comment

acolombier · 2026-02-03T22:40:57Z

Could you share some more details @daschuer? Just tested locally with WAV and everything seems to work fine on my end.

daschuer · 2026-02-04T20:30:06Z

pre-commit is complaining.

daschuer

Thank you for coming back to this. It works like a charm for mp3 and wav. Left w view final comments.

src/encoder/encoder.cpp

daschuer · 2026-02-04T20:38:47Z

src/encoder/encoderffmpegcore.cpp

 // Currently this method is used before init() once to save artist, title and album
 //
-void EncoderFfmpegCore::updateMetaData(const QString& artist, const QString& title, const QString& album) {
+void EncoderFfmpegCore::updateMetaData(const QString& artist,


This function does now only print a debug message. Is this desired? Is the comment outdated?

For some reasons, the previously set values (m_strMetaData*) was never read so this appears to have no action. I have set it to a no-op now.

src/encoder/encodermp3.cpp

src/preferences/dialog/dlgprefrecorddlg.ui

github-actions bot added engine ui preferences labels Oct 13, 2024

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acolombier marked this pull request as ready for review October 13, 2024 22:04

Swiftb0y requested a review from daschuer October 14, 2024 12:51

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feat: store tracklist as tag comment on recording

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acolombier requested a review from daschuer April 26, 2025 18:39

fixup! feat: store tracklist as tag comment on recording

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fixup! feat: store tracklist as tag comment on recording

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ronso0 mentioned this pull request Aug 18, 2025

write list of tracks played to comments tag of recordings #9134

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ronso0 linked an issue Aug 18, 2025 that may be closed by this pull request

write list of tracks played to comments tag of recordings #9134

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fixup! feat: store tracklist as tag comment on recording

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feat: store tracklist as tag comment on recording #13761

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Note on MP3

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