[API] query tag setters (and getters?) for supported tags
Submitted by René Stadler
There is currently no way to find out if a particular pipeline will be able to write out all meta data tags that are passed to it. Meta data can be silently lost currently, for example if an app allows user-supplied backends (to support arbitrary output formats, of which not all might have support for all types of meta data).
Another use case applies to using analyzers like TRM (musicbrainz fingerprinting) or ReplayGain. Applications could disable such extra processing if the results cannot be saved in the output.
Current state of affairs seems to be that encoders/muxers silently ignore any unsupported tags they encounter during iteration of passed tag lists.