[pulseaudio-discuss] RFC: Filter module loader

[pl bossart]

> Here is my first draft of a filter module to automatically load
> equalizer and/or echo-cancel modules if automagically and in a manual
> but convenient way.

Thanks for these patches, this is interesting, Arun and I were talking
last week about better support for effects, after we realized how apps
such as banshee/rhythmbox handle effects and volume ramps with awful
hard-coded gstreamer pipelines. All this PCM processing should move to
PulseAudio really.
Your approach makes sense with the existing solution based on virtual
sinks/sources, but with the current implementation, the effects are
really global, post-mix. If you want to add an effect on a specific
stream, you need to create a new sink and move the sink-input. That
really doesn't scale. Ideally we would want to use a linked list of
effects, so that the effects can be added/enabled/disabled/removed
quickly and their order modified, and we should be able to handle
- local/per-stream effects.
- global/post-mix effects
- aux effects (such as reverb)
We would also need a standard way for apps to set/get the parameters
needed by effects.
This isn't new, this is what Android/AudioFlinger/OpenSL ES implement.
In most cases, users really care about global effects only, but you
may want to have a specific filter on a stream (ReplayGain or some
volume ramp for example).
I also don't think using a 10s timer is really great to check if the
effect is actually needed. If you had a linked list you wouldn't need
to do this type of things.
let me know if I am making any sense, it's been a long week...
-Pierre