Support disc titles / ID3 frame "Set subtitle" (TSST)

[sk222 3]

The ID3 specification includes a frame called TSST (Set subtitle), defined as

  TSST
   The 'Set subtitle' frame is intended for the subtitle of the part of
   a set this track belongs to.

right below the frame used for disc number, TPOS (Part of a set):

  TPOS
   The 'Part of a set' frame is a numeric string that describes which
   part of a set the audio came from. This frame is used if the source
   described in the "TALB" frame is divided into several mediums, e.g. a
   double CD. The value MAY be extended with a "/" character and a
   numeric string containing the total number of parts in the set. E.g.
   "1/2".

Other tag formats seem so have this kind of field to, quoting https://www.blisshq.com/music-library-management-blog/2018/03/27/lamentable-state-disc-title-support/

Quote

ID3 (used in MP3) only introduced formal support in ID3v2.4 using the TSST frame. It is possible to use the same frame in earlier versions of ID3v2 but it's less likely to be supported.

For FLAC and Vorbis which, commonly, use the same tagging approach of Vorbis Comments, DISCSUBTITLE is normally used. In some cases, for some music players, you may need to use SETSUBTITLE instead.

For MP4 and WMA, this is where the fun starts. A number of tag editors have documented their mappings. For example, MP4's is documented as ----:com.apple.iTunes:DISCSUBTITLE and WMA's WM/SetSubTitle; in other words, that's where the subtitle will be stored in a MP4/WMA file if you happen to use that tag editor to save one.

I'd propose displaying the disc (sub)titles (in this example: "SURGE", "RAPTURE" and "SHIMMER") something like this:

My example is definitely not the most "real-world" one (I added the tags myself as the original album, as downloaded from Bandcamp, consists of multiple albums, each representing a disc), but there's definitely more use cases, as seen in this screenshot of the implementation in Navidrome:
https://github.com/navidrome/navidrome/issues/272#issuecomment-627497195

Edited February 23 by sk222

[Luke 39618]

Hi, yes this question has come up before and is possible for future updates. Thanks for the feedback.