Re: cs46xx -> Terratec DMX XFire 1024 4channel output success

[Benny Sjostrand <gorm@cucumelo.org>]

> Yep, 0x592d works perfectly and I also find that "0x592d" as last 
> output of /proc/asound/card0/ac97#0regs. 


Great!

> Just to get sure you didn't misunderstand me :)
> Volume control of the second output DOES work (using the 'headphones' 
> slider), but the 'PCM' slider only controls the first output's volume.
>
> I think I'm beginning to understand why:
> The second output is a pure PCM output, i.e. no mixing of CD, line-in, 
> mic-in, ... as for the first output. Therefore, there is only *one* 
> mixer element to control the second output. Only the name "headphones" 
> is misleading.
> In the new 4 channel configuration this control could have been named 
> "PCM2" or "rear PCM" or ...
> ... or isn't "headphones" sometimes the correct name?

Yeah that make sense, I was about to ask you if did'nt have a 
"Headphone" control in your mixer.

About the "Headphone" maybe a more correct name could be "Alternate 
Output", well, dont know, as that is done in the ac97 layer.

>
> That leads to the next point:
> Is it possible to switch back to the oly behaviour at run time? (seem 
> like the decision in which mode to initialize the codec is done while 
> starting alsa). Using the second output as a headphone output of the 
> first PCM device is not completely wrong: On the XFire there are 
> jumpers which you can use to select the output type (amplified for 
> loudspeakers -or- line level) of the *first* output only. The second 
> output is always at line level, i.e. suitable for 600Ohm headphones.
> I don't know whether it's a good idea to allow switching back to the 
> 2channel ("front-back-always-the-same-sound") for using headphones to 
> hear at the first output.
> I think there is an alternative: It should be possible to copy the 
> data from the first output to the second output by some .asoundrc 
> magic. But: how much CPU time will alsa eat for this (keeping in mind 
> that the codec itself can do the same without any CPU cost)? If it's 
> not too much, I wouldn't see any reason for switching back to the old 
> codec configuration.
> What do you think? (I know, you don't have the XFire, but anyway ;-) )
>  fe

To get back to the previous mode, it's just to unset the EAM bit. Maybe 
we could have a control in the mixer for that like "4 channel 
duplicate", or something that just unset/set the EAM bit when desired.

/Benny




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