'Twas brillig, and Ben C at 04/03/11 19:44 did gyre and gimble: > Thank you for your help Colin, > > The reason I'm doing this is I'm researching audio processing effects. So I need > to intercept the PCM audio stream somewhere along the chain. Currently what we > have already coded is an ALSA PCM plugin framework, so we would like to use that > to intercept the PCM audio stream to apply effects as opposed to starting over > and writing something new. > > The parameter we have to adhere to is that the original sound source could come > from ALSA or PA. We need to satisfy both. So currently we have the generic setup > where ALSA is defaulted to use the pulse plugin and redirecting everything to > PA. Then PA would use the ALSA sink "my_sink", and goes back to ALSA, where we > could insert our PCM plugin. And it turned out due to the hogging of my_sink, > we'd need to add dmix after. > > And I understand PA has additional benefits over dmix, so if there's a better > way to configure this that's more natural to PA, please let me know. OK, so this seems reasonably sensible. I guess my next question is "why is it a problem that "my_sink" is hogged? You stated that two different sources are supported: from alsa, and from PA. Assuming PA is hogging my_sink, when apps play via pulse protocol directly and uses my_sink, so all is well. When apps play via alsa, they use the "default" device which maps through to PA via the alsa->pulse plugin, which then uses my_sink, so all is well too. So I don't really see where the "hogging" problem comes in to practical effect? Just in case a random, left-field suggestion would be appreciated, a totally different approach is of course to write the filtering stuff you're doing as either a ladspa plugin and use module-ladspa-sink or even write it directly in PA based of module-virtual-sink.c code. Food for thought maybe :) Col -- Colin Guthrie gmane(at)colin.guthr.ie http://colin.guthr.ie/ Day Job: Tribalogic Limited [http://www.tribalogic.net/] Open Source: Mageia Contributor [http://www.mageia.org/] PulseAudio Hacker [http://www.pulseaudio.org/] Trac Hacker [http://trac.edgewall.org/]
