2011/4/15 pl bossart <bossart.nospam at gmail.com>: >> 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. Do the developers of those applications feel the same? Perhaps this is a right time to step back and think about what we want to achieve. I'd say that some sort of client-side access to volume ramping (fade-in/fade-out) is appropriate. But effects like equalizer is probably better off in a gstreamer pipeline. > 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 That looks awfully lot like a reimplementation of gstreamer. Is that really what we want? > - local/per-stream effects. > - global/post-mix effects > - aux effects (such as reverb) I consider the global reverb option one of the most terrible parts of a lot of windows audio drivers. What's the use case for that? > 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 I'm sorry for sounding perhaps a bit grumpy, but I am a bit hesitant. This is really something that should be planned carefully. PulseAudio can't be everything for everybody. That said, it is perfectly possible that I miss some important usage scenario's, especially you seem to be working on embedded stuff, with other demands on pulse. Maarten
