[Playlist] Nested Playlists, Embedded Fields (was: We need to reset the site

[Kace Ong]

Since I see that my old questions from 22-Jul-2015 has been added to
the gitlab issues
(https://gitlab.xiph.org/boehs/xpsf-spec/-/issues/3), please allow me
to add more context to my issue.

The original question is whether XSPF allows custom tags and nesting
of playlists.

1. Playlist of playlists: say song A, B, C are a group file, and song
D, E, F are another group file.  Then I may want to be able to create
a third file that simply refers file 1 and 2 as child objects, without
having to explicitly write out their contents.

2. Within the definition of a playlist sequence, a song is defined by
an absolute location/URL.  Sometimes this is undesirable, e.g. if the
song's absolute location cannot be determined.  For instance, a set of
song files on a portable storage is sometimes mounted on D: drive on
one PC, and as F: drive on another PC.  This breaks the playlist.

  - 2a. So sometimes what is desirable is to have a file location
which is resolvable at runtime.  This may mean some extra user defined
fields in XSPF specs, e.g. a custom field called DRIVENAME=D and
allowing file locations to be expressions.

  - 2b. In the world of online music, due to various rights and
permissions concern, a song repository may be linked only temporarily
at https://mymusic.com.  This means any playlist pointing to this
repository has to resolve the domain name.  It is then easier to have
a custom field called REPOSITORY=https://mymusic.com instead of that
string in every song address.

  - 2c. Both 2a/2b cases can be just a macro or variable substitution.
But here is another situation that is possibly more complex.  A DJ at
location 1 wants to play his music at location 2 remotely, which is a
fairly common scenario in today's world.  Usually he sends the
compressed audios from location 1 to 2.  But what if he sends his
playlist instead and have it executed at location 2?  Then the remote
side gets to hear full resolution music.  But this can work only if
playlists can travel and still resolve resource addresses correctly.

3. For the advanced music hackers, can we use scripts to automate
playlists?  A case example would be a Karaoke, which has a music and a
lyric components that need to sync with each other.  Another case
example is a lecture, where we want the sequence to pause at a point
until the user presses a key to continue. A playlist is essentially a
script, but currently the script only has the power of a simple
sequence and no conditional / subroutine / parameters.  How to create
more flexibility?

  - 3a. One example application could be to export playlists that
mixes Spotify and Youtube music.  Each has a different URL scheme, and
some tricks are needed to export their playlists which are custom
formatted.  Exporting them to XSPF may require custom tags specific to
each.

Possibly one simple solution is to combine a powerful scripting
language (like python) with XSPF as a data structure. But XSPF should
define the behaviour of undefined or unknown tags and provide test
suites.

p.s. I am not aware what is the problem with Mailman, other than a
very old user interface. Obviously Gitlab can be an improvement  but
only if you know how to use it.