[pulseaudio-discuss] alsa: split up 6-channel streams into 3 stereo pairs?

Daniel Mack zonque at gmail.com
Wed Nov 16 03:19:43 PST 2011

On 11/14/2011 08:27 PM, Tanu Kaskinen wrote:
> On Sat, 2011-11-12 at 17:14 +0100, Daniel Mack wrote:
>> A 6-channel audio device I wrote support announces a single ALSA
>> subdevice that has to be opened as a whole in order to access all six
>> channels. However, I would like to offer the channels as three pairs of
>> stereo (for both directions), so stereo clients can be routed to each of
>> them individually.
>> From what I saw in the alsa-mixer module code, there is no way to
>> specify such things of settings in the profile-sets, right? Are there
>> any plans to support these kind of setups?
> So even if the card would be used as three stereo pairs, Pulseaudio
> would still have to open the device with six channels, right?

Exactly. All other attempts to open the pcm will fail.

> There's module-remap-sink, which can be used to split a six-channel sink
> into three stereo sinks (while keeping the six-channel sink also
> available). For sources there's currently nothing. You're right in that
> there's no way for you to write a profile-set configuration file that
> would make the stereo sinks available out-of-the-box.
> As for plans, I don't think there are any plans to do anything about
> this in the near future. I think Colin has mentioned that a GUI for
> configuring this kind of things would be nice, but that's about it. This
> is the first time I hear the idea of extending the alsa-mixer
> configuration to support this kind of setups. Sounds like a good idea.
> Now if we just could find someone to do the work...

I would, if I only had the time ;)


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