[MPRIS] User rating read-only

[Alex Merry]

On 02/05/12 11:43, mirsal wrote:
> However, rating a track might not be the same thing as simply replacing
> the 'userRating' metadata entry (media players might want to mix manual
> and algorithmic rating or have multiple sources of rating, see:
> https://gitorious.org/xdg-specs/xdg-specs/blobs/master/specifications/FMPSpecs/specification.txt )
>
> It might then be a good idea to handle rating separately, perhaps by
> using specific a method for that purpose.

Well, media players can do what they want with the value they receive; 
client should never assume with the MPRIS2 interface that asking the 
media player to set a value (eg: when seeking) will actually cause that 
value to be set.  They should be listening to the PropertiesChanged 
signal instead.

I think userRating is fairly clearly "the rating that the user has given 
this track".  Xesam also has an autoRating element.  I guess we could 
define values based on FMP as well.

We have a more general issue with metadata, which is that Xesam is 
dead[1] (long live Nepomuk[2]).  The Xesam spec is no longer available 
online, except some old versions on the Wayback Machine.  I don't know 
what we want to do about this; we don't want to break compatibility, but 
there is not really a reference available for adding more "standard" 
elements (which was the original point of using Xesam).  I guess we can 
add mpris: elements as and when we feel they are needed, though[4].

I should point out that I don't think using Nepomuk is sensible for our 
purposes, as that is an RDF ontology not really suited for a metadata 
list like we have.

Alex



[1]: http://trueg.wordpress.com/2009/04/29/xesam_vs_nepomuk/
[2]: http://www.semanticdesktop.org/ontologies/
[3]: 
http://web.archive.org/web/20081012050951/http://xesam.org/main/XesamOntology90
[4]: http://freedesktop.org/wiki/Specifications/mpris-spec/metadata