Frescobaldi, improve support for audio export

[Urs Liska]

Hi all,

I've just started looking into how Frescobaldi provides support for "exporting" scores to audio.

Until now this was hardcoded to use TiMidity (and had to be activated as "experimental feature").

I have so far created functionality that

• checks whether timidity, fluidsynth and lame are available
• populates the filter of the file dialog with all registered file formats for the available converters (=> if (and only if) Lame is installed the .mp3 filter will be added). You can see a screenshot at https://github.com/frescobaldi/frescobaldi/pull/1205#issuecomment-543155209

After clicking the Save button there will be a configuration dialog like we already have for the file *import* functionality. Depending on the chosen converter/exporter tool it will be possible to configure selected settings like for example audio quality, alternative soundfont (in fluidsynth), effects.

However, since that's not my area of expertise I'd like to ask for suggestions (possibly with the corresponding command line invocations) about

• which audio formats Frescobaldi should support (I don't think it's good to clutter the interface with stuff that noone needs)
• which options we should make configurable for the three converter tools
• if there are other converters we should consider supporting

Best
Urs