Re: CMI973, patch and alsa release

[Takashi Iwai <tiwai@suse.de>]

At Tue, 3 Feb 2004 01:32:49 +0800,
C.L. Tien <cltien@cmedia.com.tw> wrote:
> 
> Is there a better way to do digital volume tuning without loss of
> cmpatability , especially for OSS applications? In the Azalia spec,
> PCM volume/mute is optional so there will be codecs without volume
> controls. 

i believe the best way is to implement the dynamic software
attenuation in the alsa-lib, and uses aoss wrapper for the OSS
apps.  in this way, you can emulate the AC3 easily, too.

in the kernel emulation route, it's hard to implement cleanly.
for example, the software attenuation doesn't work with mmap mode
(unless you don't do it in the DMA interrupt context - which is really
 bad idea). 


Takashi


> 
> Sincerely,
> ChenLi Tien
> 
> -----Original Message-----
> From:	Takashi Iwai [mailto:tiwai@suse.de]
> Sent:	2004/2/2 [星期一] 上午 06:19
> To:	Jaroslav Kysela
> Cc:	Davodet Olivier; alsa-devel@lists.sourceforge.net
> Subject:	Re: [Alsa-devel] CMI973, patch and alsa release
> At Mon, 2 Feb 2004 09:06:37 +0100 (CET),
> Jaroslav wrote:
> 
> well, let me clarify more the problems.
> 
> - the patch copies the whole audio data with the software
>   attenuation.  we don't want this in the kernel context.
>   this should be the job in the user-space, pereferrably in alsa-lib.
> 
> - the patch introduces float calculation.
>   it's not allowed at all in the kernel code.
> 
> 
> the control of ac97 mic and line sharing is a good point.
> the similar thing can be implemented more easily by the alsa-lib's
> hook plugin, though.
> 
> 
> Takashi
> 
> 
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> 


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