LV2 Support

[badescunicu]

This PR adds basic LV2 support to Mixxx. It integrates seamlessly with our current Effects Framework. Just install an LV2 plugin and it will show up when you cycle through the effects.

Currently it is only supporting plugins which handle stereo input/output audio samples and do not require any additional features. Some plugins which were tested by me: Calf Phaser, Calf Flanger, SWH Karaoke.

[daschuer]

The logo has the wrong ratio. It should not be stretched.
Please use the "Simple versions for bright backgrounds" from http://lv2plug.in/logo/

[daschuer]

Hi Nico,
this branch works quite good from the audio processing part, but needs a lot of fine tuning to be merge able into master branch.
Here some pending issues:

• Blacklist: We need to be able to blacklist Plug-Ins that are known to be useless for Mixxx like
  "Stereo to MS"
• We need also an option to hide plug-Ins from the GUI because they will not be used by the DJ.
• The same for the Parameters. We need an option to hide unwanted parameter knobs
• We need a "More" popup for plugin with more than 8 usefull parameters parameters
• We need a widget that deal with long effect or button names.
• ...

[daschuer]

• The LV2 plug-ins in preferences should be listed in a list view.
• It should contain an "Info" button displaying exactly the info that is displayed by lv2Info from the lilv2-utils package.

[rryan]

I must have missed adding samplerate COs to GroupEffectProcessor (I think it may introduce less coupling between the engine and the effects system if the current samplerate is passed into the initialize() and process() methods) but the delete in the destructor (a few lines down) should be moved into the EffectProcessor destructor.

[rryan]

Nice!

[esbrandt]

Spelling LV2 Plugins

[esbrandt]

What are the default search locations for installed lv2 plugins?
On OS X, plugins in /Users/foo/.lv2 wont show up.
Any of those paths valid: http://manual.audacityteam.org/man/Effect_Menu#LV2_Effects ?

Edit:
There is the following error message in the logs: Error opening file /Users/foo/.lv2/bundles/manifest.ttl (No such file or directory) lilv_world_load_bundle(): error: Error reading file:///Users/foo/.lv2/bundles/manifest.ttl.
Using the lv2 plugins from https://github.com/swh/lv2/ , the folder structure on my machine looks like .lv2/bundles/a_law-swh.lv2/manifest.ttl, with the manifest.ttl being in the single effects subfolder.

[ywwg]

does this work on all platforms?

[badescunicu]

Currently it works on Linux. It should work on OS X (must investigate @esbrandt's issue) and on Windows too, since lilv is cross platform. However, in order to work on Windows, this[1] must be modified to take build.platform_is_windows into account.

[1] - https://github.com/badescunicu/mixxx/blob/lv2_support/build/features.py#L1332

[rryan]

looks like a tab made it in here

[rryan]

I'll add lilv to our build environment so we can start making builds of this with the build server.

[mixxx-buildbot]

safe to test?

[rryan]

skip ci