Re: [Ekiga-list] Alsa device enumeration

[Damien Sandras <dsandras seconix com>]

Le jeudi 12 mars 2009 à 20:41 +0100, Alec Leamas a écrit :
> 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?

I'm not sure. How can we know surround is non sense? How can we know
other similar non sense entries... To my eyes, Alsa is really purely
broken :-/
-- 
 _     Damien Sandras
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