[pulseaudio-discuss] New feature in the works: "flat sink"

[Tanu Kaskinen]

Hello,

When we have a filter sink that does some processing, currently the
benefits of the flat volume feature are not really available. That's
because if you have a music player that is connected to the filter sink,
the hardware sink doesn't have any idea of the music player's stream
volume.

In order to fix this, Pulseaudio 0.9.15 on Maemo 5 was hacked to
implement a feature that was dubbed "flat sink". The feature is still
needed in Maemo 6 / MeeGo, and now we are finally trying to get it to
upstream. The "flat sink" feature (better names welcome) works so that
the filter sinks that want to avoid the previously described problem
declare that they don't want to have independent volume, but they follow
the master sink volume instead. Then the volume logic is changed so that
the hardware sink calculates its real volume using also the streams
connected to the filter sink in addition to the streams that are
connected directly to the hardware sink. Basically we're trying to
create an illusion that from volume point of view all streams are
connected directly to the hardware sink, thus the stack of sinks
collapses into a "flat sink".

I hope that sounds like something that can be merged to upstream. There
will be several patches, and I just sent the first. The rest of the
patches are not ready yet - I'll send them as I finish them.

-- 
Tanu