One of the key things I've looked for in a playlist format for many years is the ability to handle files that contain multiple tracks. My main example of this is continuous DJ mixes that are a single file. You might also see this in live recordings of performances where the interaction with the crowd between each song.

These single file media items generally have 1 or more Album Artists (e.g. the DJ) with each track in the performance blending into the next. Each track may have an associated Artist and Track name. Conventionally the best approach to solving these is to use a Cue sheet and a plugin for whatever media player that can load these simultaneously. Alternatively (though rarely) a container format that supports chapters / sub streams (e.g. mka) can be used.

I don't see a secondary (CUE sheet) format as being the right solution to this problem. To me a playlist and a list of tracks played in a performance are kind of the same thing and should be handled by the playlist.

My proposed extension to the UPL format is to allow each playlist entry to specify a part of the identified file. Now there's two possible ways of doing this:

1. Sub items under the entry (e.g. chapters)

2. Each entry specifies a start and end time (or duration)

You mention at [1] that this format is about display, I feel this fits within that idea by being something that is otherwise difficult to display using any other available info (ID3 tags etc.)

[1]: https://gitlab.com/universal-playlist/universal-playlist-spe...