[alsa-devel] Surround problems with cs46xx

[Takashi Iwai]

At Sat, 16 Jun 2007 16:56:53 +0300,
Vasilis Manwlopoulos wrote:
> 
> Hi,
> 
> 
> Sorry for bothering the list again, but I have major problems with the 
> surround 5.1 sound. I have manually compiled/installed th latest 
> alsa-1.0.14 drivers but nothing improved. I am using Ubuntu 7.04 and my 
> soundcard is  the Hercules Fortissimo III. This is, as far as I know by 
> reading on Internet, supported by the module snd-cs46xx in ALSA. I have 
> enabled the surround sound by creating the following .asoundrc file.
> 
> pcm.!default {
>     type plug
>     slave.pcm "surround51"
>     slave.channels 6
>     route_policy duplicate
> }
> 
> 
> The problem is that sound pauses whenever I try to do something "heavy" 
> such as opening a new firefox window or generally another app. Also, 
> there are delays and echo between the front and the rear speakers from 
> time to time. I think that the problem is that, this alsa setup(meaning 
> surround5.1 and the specific soundcard) places a heavy load on the cpu. 
> There are 99% cpu usage times when the only thing active is a player 
> playing a "normal bitrate" mp3. When I delete the .asoundrc file and I 
> switch to default stereo sound using only the 2 front speakers the 
> problems disappear.
> 
> Can anyone suggest anything about this?

First, try to investigate whether it's a problem of surround51
implementation or rather the "default" definition above.
For example, prepare a 6-channel WAV file, and play directly with
surround51 PCM.

But, from the symptom, I'm afraid it's rather a hardware problem.
The cs46xx uses three stereo streams for 5.1 output, and they are not
strictly synchronized.  And, debugging cs46xx driver is really a
nightmare...


Takashi