[pulseaudio-discuss] specifying ALSA mixer control

Colin Guthrie gmane at colin.guthr.ie
Fri Mar 27 01:36:57 PDT 2009

'Twas brillig, and Lennart Poettering at 26/03/09 23:11 did gyre and gimble:
> On Thu, 26.03.09 20:51, Jens Peters (jpeters7677 at gmx.de) wrote:
>> Lennart Poettering wrote:
>>> I doubt that it would be so useful to expose this in PA anyway. I
>>> mean, how realistic is it wanting to drive both SPDIF and analog audio
>>> at the same time from the same sound card? Appears to be a very exotic
>>> niche usage to me.
>> Please don't forget the combination of spdif and headphones. I'm quite sure 
>> I won't be the only one using spdif for "normal" audio listening and 
>> simultaneously a headphone for voip stuff. 
> This might actually be a valid point.
> However, as mentioned it's a bit hard to detect these cases and
> distuingish them from cards that do hw mixing. If ALSA would give us a
> bit of a hint here we could certainly add this.

So from your original comment, is it possible that some hardware lets 
you open the mutually exclusive bits, but only errors out when you try 
to write a sample to them at the same time?

If so, is it possible to try and do a bit more foo where a few samples 
of silence is written during probing to detect this?

You could then up the pulse probing to a 2-in+2-out approach? (or even 
just a 1-in+2-out) That way it would probably cover 95% of the use cases.

Just some thoughts without knowing the complications involved :)


Colin Guthrie

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