Re: [Ekiga-list] Alsa device enumeration

[Alec Leamas <leamas alec gmail com>]

Damien Sandras wrote:
> Le mercredi 11 mars 2009 à 20:46 +0100, Alec Leamas a écrit :
>   
> > There are  some problems w the current code which enumerates the alsa 
> > devices. I have a sketch for a patch, this is really not that 
> > complicated these days, there are new library routines which support it.
> >
> > The problem is just what devices to show, and how. Basically, there is 
> > two kind of devices: the classic devices which we partly see today, and 
> > several "new" devices such as pulse, hdmi, and several surround*. They 
> > exist for both capture and playback. The list for my box is below. The 
> > basic ideas are stolen from Skype. The important thing is the left 
> > column, the right is just internal stuff (hey, use a fixed font to see 
> > this...). 
> >
> > Any thoughts out there about this list?
> >
> >     
>
> I would clean it and remove entries with hw only. Because that's
> complex. What is Surround40 capture ?
>   
Surround capture is in my eyes complete nonsense. It's reported, though. 
I totally agree that it should not be visible to users.

The hw discussion is complex. Actually, there are documents on the alsa 
site which boils down to that using hw:/plughw: is deprecated, they 
recommend "front", "surround*" etc. But for capture, it just makes no 
sense. And, more important, if you have more than one card there is no 
way to e. g., direct sound to "device front at the usb headset". Which 
device "front" actually refers to is a part of fthe alsa configuration 
(normally the default device). So, to direct sound to a specific card 
you must either mess with the alsa configuration, or use the 
hw:/plughw:. This is my current understanding.  I know there are people 
who knows more which is reading this...

My basic impression is that the alsa device addressing schema is  a bit 
hard to handle, especially with more than one card. And although it's 
not that common that users have more than one card in their box, USB and 
bluetooth headsets are important use cases involving more than one card 
from the alsa perpective.

It's also important to sort out the different roles in device 
management. The ultimate goal in my eyes is to create a new UI focused 
on making it much easier to setup the sound system.  The major task is 
really up to the UI code here. My basic view is that the driver should 
provide a reasonably complete list of devices with as much information 
as possible.  This does not preclude hiding nonsense like surround 
capture, But the finer tricks should be done by the UI, and we should be 
careful not to hide to much in the driver. The UI has other options than 
to just take the list from the driver and place in a select box IMHO.

The plughw/hw is indeed complex. But to my understanding, it's really 
the only way to fix the basic task "Send sound to and get capture from 
the USB headset/main box/bluetooth headset".  Of course, we could handle 
this by reconfiguring alsa. But since devices comes and goes away, and 
then comes back with a new number (sigh...)  this is not that easy. 
Maybe the complexity of hw/plughw could be handled by a new UI?

--alec