The patches I am about to post provide two modules that could be of interest to the PulseAudio community. module-virtual-sink is a template for the addition of PCM processing. It's basically based on the LADSPA module, I use it for internal experiments and will enhance it in the future. module-virtual-source is something new. This is the continuation of my earlier work to enable paths that were not possible in PulseAudio. With module-loopback I enabled a source to be played on a sink. Well, this virtual-source module is the missing complement. It wasn't possible until now to mix music with the microphone inputs. Now you can send data to the 'uplink sink' exposed in this module, and it'll be mixed with the inputs and provided to apps by a virtual source element. For example you could be talking with Skype and sharing your music with the remote party. Or send beeps/tones/alerts/DTMF/whatever. Or record a conversation. In addition, this virtual source can be used to add PCM processing on the inputs if you don't care for this mixing capability but want to add EQ, DRC, on a capture path. I played for some time with the idea of adding such a mixing capability for all sources, just like we have monitor sources on all sinks, however you may want to do some processing on the inputs before mixing, and I preferred to implement this mixing capability as an optional feature in a separate module. I did struggle to implement some of the callbacks; this is fairly hairy PulseAudio stuff, you will see a lot of FIXMEs on the code handling latency/state/volume changes. Contributions are welcome to stabilize the code. One known issue: I added some code to wake-up the source when the virtual sink become active, but at some point the suspend-on-idle kicks in and the client gets stuck. I need to find a way to prevent the source from being suspended in that case, even if no client is connected to the source. To enable both modules, just add these lines in default.pa load-module module-virtual-sink sink_name=vsink set-default-source vsink load-module module-virtual-source source_name=vsource uplink_sink=uplink set-default-source vsource You can then test all this with pavucontrol and reroute the data wherever you want. Thanks for your feedback. Cheers, - Pierre
