Portable plugin graph

[atsushieno]

Right now, when we use this tool to define audio plugin graphs for each track, those plugins are recorded as bare filtergraph generated by AudioPluginHost. When we switch environment across platforms, those plugins become different (they would be AU on Mac, and they would be VST3 on Windows and/or Linux, or LV2 on Linux). Since my secondary purpose of this project is to support AAP, it has to be also portable to Android too.

Since they don't share the same set of plugins, it is song author's responsibility to use the set of common audio plugins. But even if they use only such plugins, those filtergraph files from AudioPluginHost is platform dependent.

Maybe there should be some kind of mapping aliases, or at least per-platform filtergraphs. But the fundamental problem lying around here is, what is an "identical" plugin? Some possible usage scenarios:

• I use Collective on Linux (VST2), Mac (AU), and Windows (VST2). They are portable across those desktop. Are they "identical" ? They should be.
• I use different versions of Collective on those platforms. Are they identical? They probably stll should be.
• I use ADLplug AU on Mac, and ADLplug LV2 on Linux. Are they identical? Yes. But how about portability? They wouldn't share the same "state" binary blob. Also, do they share the same parameter set?
• What if I use ADLplug on Linux as LV2 somewhere, and ADLplug via lv2vst i.e. as VST2 elsewhere?

Can we cover some or all of them?

[atsushieno]

AudioGraph element is now given a name, meaning that it is somewhat more abstract than before.

[atsushieno]

Some relevant web resources (will be updated):

• https://www.kvraudio.com/forum/viewtopic.php?t=285627
• https://www.kvraudio.com/forum/viewtopic.php?t=397199

[atsushieno]

I tried loading OPNplug's JUCE-VST3 state on aap OPNplug (which is JUCE-AAP), but turned out that the state is VST3-specific and not immediately portable on AAP. Yet the content seems to be just wrapped and the content may be still reusable.

[atsushieno]

...That however involves manual importing and it cannot be regarded as "implemented".

[atsushieno]

I have integrated jlv2 into augene, as well as build scripts for AudioPluginHost to add LV2PluginFormat, so that I can use LV2 plugins along with VST3. It would also help bringing in portable LV2 plugin graphs.

[atsushieno]

For LV2 plugins, there is LV2_State_Map_Path feature that should be provided by the host of which a plugin can make use to convert absolute and abstract file paths. https://lv2plug.in/doc/html/group__state.html#structLV2__State__Map__Path

It is used by sfizz for example, so that SFZ files are stored in abstract form, not immediate path.

[atsushieno]

Even for the same JUCE plugin project sources, the uid on VST and AU are different. They need certain mappings.