Stereo sound to 5.1
 

Hi! Is it possible to mix a stereo sound (music for example :)) to 6 channel? Now I use the "Four channel mode" feature in alsamixer, but it only uses the front and the rear speakers, but the centre speaker remains silent. When playing 5.1 sound, it works fine. The subwoofer works, but at a very low volume. On windows, the sound driver could use all the 6 channels, and the subwwofer was much louder. I have a CM8738 sound card and a Trust Soundwave 2000P speaker system. Thanks for the help!

It's actually handled by the sound player for music. Xmms, for example, will play multichannel when using the alsa plugin. It's not true surround, but kind of an intelligent remix (as most music is only recorded in stereo). Also, it depends on whether or not the sound driver fully supports that chip. In alsamixer, you should have controls for Front, Rear, Center, and LFE, if it supports 5.1 channel (Side will also be there for 7.1 surround). If you only have Front and Rear, then you only have 4 channel support.

If you are feeling adventurous, you can try installing the latest snapshot of alsa. Download the driver, lib, and utils at a minimum. Compile them and install. Rerun alsaconf to make sure it is configured correctly.

I don't have even front and rear channels in alsamixer :(
I only have these:
Master
3D Control
PCM
Synth
Line
Line-In
CD
Mic
Mic Boos
Mic-In M
Phone
IEC958 5
IEC958 C
IEC958 I
IEC958 I
IEC958 I
IEC958 I
IEC958 L
IEC958 O
PC Speak
PC Speak
Aux
Four channel mode

In xmms, if I choose surround51 for device, it starts playing, but the speakers are silent. I use alsa-cmpci module for my sound card. If it doesn't fully support this chip, than how can it play 5.1 DVD-s correctly?

Like I mentioned earlier, you may want to upgrade to the latest alsa version. If you type "cat /proc/asound/version", it will tell you what version you are running.

What distro are you running? You mentioned Mandriva, but your profile indicates Fedora Core 2.

I use Mandriva 2006, my profile was old :)I use alsa 1.0.9b, that comes with Mandriva. I couldn't find a newer rpm.

You won't find a newer rpm for a little while. Alsa 1.0.11 just went gold last Tuesday or Wednessday. It won't make it to Mandriva until their 2007 edition at the earliest (beta starts mid September). I'm working on a packaged version next week for work, I'll let you know how it goes. It's GPL, so there's no reason I couldn't share it. I just don't have anyplace to post it to.

What kind of bandwidth do you have? I could email you the driver rpm built specifically for your system, or I can email the big package (all drivers - easier to build, but bigger download).

That would be great! Thanks. I have 1.5 Mbps connection, so you can email the big package. But I have only 25 Mb space in my email account. My adress is sevcsik@citromail.hu

Well, it may take a little longer than I had hoped. I'm having issues with the driver in Mandriva (kernel segfaults). I've reverted back to 1.0.9b (default), and will plug away at this issue tomorrow.

It may be a few days before I get this figured out, so be patient. I'll get back to you as soon as I feel it is semi-stable.

Ok. Keep up the good work :) Thanks

Ok, I think I have it ready to go for now. There are still a few kinks to fix, but it is running on my system just fine.

I'll send you the alsa-lib, alsa-lib-devel, and alsa-utils in binary rpm form, but the driver you should rebuild, simply to make sure it matches the kernel you are running. You'll need to rebuild and reinstall it each time you get a new kernel.

Thanks, I installed it, but nothing changed :( Now I swapped the rear channel with the center/subwoofer, so I have bass :) Thanks for the help

I'm seeing some interesting behaviour too. In testing my 5.1 surround, audio is distributed equally between the channels (i.e. Front right, rear right, LFE are te same, and front left, rear left, and center are the same).

More debugging....

For me, the Center/LFE channel gets nothing :(

Check your mixer settings with alsamixer (open a console window, and type alsamixer at the prompt). To unmute different channels (marked with an mm), press m. Q and Z are Left up and down (for the stereo channels), W & X are both channels, and E & C are the right channels. It's kind of easy to figure out from there. Tab selects between playback, capture, and all channels showing.