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Metadata musings

Posted: Mon Mar 06, 2017 8:18 pm
by MDE
Posting this here as I would like to generate a little discussion before making any feature requests.
If you only have pop music, then your metadata needs are fairly simple and easily met. However, if you are a classical or jazz fan then it is likely that your metadata is more complex. I'm not really into jazz, but I do have quite a lot of classical music and have documented my approach extensively at http://music.highmossergate.co.uk. Muso lies at the core of this approach, but since it is not a ripper/player/tagger, it has to exist in the context of other software. In my case, that is principally Logitech Media Server ("LMS") and squeezebox touches for playing, dBpoweramp for ripping/converting/initial tagging and mp3tag for tag maintenance. I also use iTunes for my portable music.
Not having control over the entire "ecosystem" creates headaches for metadata management, even within such a flexible solution like Muso.
My solution has some core principles:
  1. If amending tags to create a particular effect, never lose the underlying data - so that recreation is always possible
  2. If using a script to amend tags, write it in such a way that re-applying it to a file always has the same result - i.e. it has no effect on a file to which it has already been applied
  3. If importing and exporting tags from a tool (e.g. Muso), keep it symmetrical i.e such that if the data has not been deliberately changed inside the tool then the exported tags should be exactly the same as the imported ones
  4. Always use the simplest approach possible to get the desired result
I think these are useful principles regardless of the particular solution.
There are a couple of areas, however, where it has not been easy, or even possible to bridge the gaps in the ecosystem components and stay true to these principles.
The first area is the Title tag and this post only concerns that (the other is about artists, performers and instruments and I will post on that later).

In LMS, only one title is allowed for display purposes. However, classical music is more complex than this, with a Title usually having at least two components (Work, Movement) and maybe more. Muso copes with this by using the Group Header field for "Work". However, on choosing this option, only the Movement goes in the Title field. If this is then exported, the Title field no longer has the complete title - breaking rule 3, and maybe rule 1 too. Jeremy has cleverly catered for this by allowing the Title to be structured as "Work: Movement". If "Work" is also imported into the Group Header, then the Title tag will be maintained in full, but only the movement will be displayed (under the work) on the album screen. Arguably, this is a bit of a hack, although it is consistent with much of the external metadata sources - and also consistent with the the approach to sub-headers in Muso, where "::" is used to separate the Group Header from the Sub Header.
iTunes has now thrown a bit of a googly with its introduction of new tags (mp4 only) for work and movement, with a "flag" tag (Show Work Movement) to determine if Title is displayed or Work & Movement. Would it make sense for Muso to go down this route (even though it is iTunes-specific), or are there other, compatible, but better approaches? I can see problems with exports: if say Movement is amended and exported, then it will not be consistent with Title, if that was in the format "Work: Movement". I have checked this in iTunes and confirmed that the "Song" title is independent of Work & Movement. Alternatively, the current hack could be removed and instead a flag could determine that the export of Title will be in the format "Work: Movement". There may be other ideas which may be better. I'll also take a look at what other approaches are out there.
Comments?

Re: Metadata musings

Posted: Tue Mar 07, 2017 3:35 pm
by musoware
I have noticed that the tags that iTunes writes for these new attributes for .m4a files appear in the dbpoweramp tag editor as tags 'Work', 'Movement Name', 'Movement Number', 'Movement Count' and 'Show Work Movement' but do not appear in mp3tag at all, similar to 'Performer'. Whether I can get at them through my tag reader is uncertain at this stage.

I could introduce these tags into Muso and drive the album display off these rather than title, but I'd only want to do this if this becomes a tagging standard rather than something iTunes-specific. If I did this 'Work' would have to support the two levels that GroupHeader currently does (through the :: delimiter).

I think as Muso is primarily an LMS front end I'd also like to see which direction LMS takes in this area before I change anything. What's there works pretty well right now.

Re: Metadata musings

Posted: Sat Mar 11, 2017 8:39 pm
by MDE
I agree, provided the existing support for Title=Work:Movement continues. I'm continuing to look at ways of simplifying and improving my "classical" scheme and I think that Work:Movement is important to have Muso and LMS working well together. As part of my more general review, I am trying to get my head around the inconsistent and developing ways of dealing with tagging, as implemented in various leading apps. I am tending to the view that consistency with MusicBrainz is the most useful approach. The MusicBrainz style guide for Titles in classical music is also Work:Movement (or Work:Part).

Re: Metadata musings

Posted: Tue Mar 14, 2017 8:21 am
by musoware
Yes we'll keep Title=Work:Movement and GroupHeader=Work (where Work can also have suffix ::Part) until LMS make a move on this.

Added some notes to this effect here:
http://musoware.com/wiki/index.php?titl ... ic_Support

Re: Metadata musings

Posted: Thu Mar 16, 2017 5:05 pm
by DuLac
musoware wrote:Yes we'll keep Title=Work:Movement and GroupHeader=Work (where Work can also have suffix ::Part) until LMS make a move on this.

Added some notes to this effect here:
http://musoware.com/wiki/index.php?titl ... ic_Support
My collection is made of jazz mostly. Quite at lot of historical recordings. I find these features extremely elegant and very useful for some extra notes regarding a given tune. Thanks.