[linux-audio-dev] ALSA features.

[James Courtier-Dutton]

Esben Stien wrote:
> James Courtier-Dutton <James at superbug.co.uk> writes:
> 
> 
>>any feature requests that people who use this list would have.
> 
> 
> Fixing plug:jack. As of current, it does not work with devices that
> read and write to the device at the same time, such as voip
> applications.

VoIP application should really be opening the ALSA device twice, once 
for playback and once for capture. The reason for this is that a lot of 
sound cards have different buffer sizes for capture and playback and the 
only way to have proper control over these is to open them separately.
There is also the matter of sound routing. If you just opened it once 
for full duplex, how could you select which mic and which speakers the 
sound will come from. By opening each channel separately, one can decide 
to route the sound to the correct place. E.g. playback device could be 
"plug:front" or "plug:rear" and the capture device could be "default"
I know for a fact that all Creative sound cards will fail VoIP apps if 
they are opened with a single device in full-duplex, but work fine if 
two devices are opened, one for capture, and one for playback.
It is my advice to fix the VoIP apps instead.

> 
> In my case I use asterisk. 
> 
> I've opened a bug on this issue: 
> 
> https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1324

Sorry, I cannot help you with this problem. I don't work on the jack 
bits of ALSA. I don't actually use jack or Ardour much. I have installed 
Ardour in order to find out just how difficult it is to use unless you 
can get the gain levels correct in alsamixer, and having alsamixer 
currently doing just % measurements makes it next to impossible to get 
right unless one looks in the alsa source code and the appropriate data 
sheets. It is this reason why I am aiming to work on converting the 
alsamixer to display where the 0dB gain/attenuation point is, so that 
the Ardour application can then know that the sound card will pass the 
sound in and out of Ardour without modifying it.

> 
> The package alsa-plugins, which has the plug:jack code just went from
> 1.0.9 to 1.0.10rc1 without a single code change to the pcm_jack.c
> file, so that was a little sad;)
> 
> 
>>Any other suggestions?
> 
> 
> Implement alsamixer as a daemon and add osc support, then make it work
> with rme devices not currently usable with alsamixer, such as the
> multiface.;)
> 

alsamixer is already like daemon. One can connect as many mixer control 
apps as one likes to the alsa mixer control api.

OSC to me seems like just another network audio method. Does OSC include 
a mixer api? ALSA currently only intends to handle sound cards. I would 
have thought that jack should just write another module to talk to OSC, 
much like jack currently talks to ALSA. I don't see why ALSA should 
support OSC.