why cant Alsa sound drivers cant play 2 things at once?

nejiron

is it because only one thing can gain access to the sound card device at a time and it is not preemptible? Also does it not allow the interleaving of outputs to the sound card?

In my opinion I like it better the way windows does it where it overlaps the sound rather than waiting for one to finish. I am tired of having to hit play again on xmms because I get an instant message that requires the sound driver. (xmms says cant get control of the sound card, and stops playing rather then trying to keep get control)
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adaptr · Posted: Tue Mar 01, 2005 5:32 pm Post subject:

That depends entire on the implementation used by ALSA.

If Windows can do it, you may bet that Linux can do it better - it's not like you suddenly aqcuire magical new hardware capabilities when you stick in a Windows CD...

There are a number of separate issues at work here:
1. does the actual physical sound card support (i.e. have) hardware-based mixing ? this is readily discovered by the presence of terms like "64-channel sound" anywhere in the docs or on the card - that would mean the card itself supports 64 concurrent output streams, which it then mixes itself.
2. If the card supports hardware mixing, is ALSA actually using this ?
3. does the application use ALSA, or does it write directly to the /dev/dsp device ?

The last is probably relevant here - one of the functions of ALSA is to move the playing of sounds from the actual sound device to an abstract layer above it, multiplexing any signals sent to it before sending the final mixed sound output to the dsp device.

Native sound:

z3ro · Apprentice Joined: 16 Jun 2004 Posts: 261

Have a look at the Alsa Project website, and find your soundcard there. It will be under the "SoundCards" option at the top of the page.

Usually there will be a sample ".asoundrc" file there, this is what you need to get the playback of multiple streams working - it uses the dmixer plugin.

curtis119 · Posted: Tue Mar 01, 2005 5:51 pm Post subject:

MS uses an abstraction layer called "DirectSound". DirectSound is nothing more than a little server that sits in the background and all audio streams are sent to it. It mixes them together and then sends the result to the sound card for playing. It is the EXACT same thing as Esound or Arts or Jack or dmix(dmix is actually a little different but for your purposes it is the same as the rest). The only difference is that windows programs only have DirectSound to choose from so they all use it by default. In the Linux world you have to choose which software mixer you want to use and then set up all your apps to use it. Or you can setup dmix and just have all the apps use the default alsa device (I find this to be the easiest solution since almost all alsa enabled apps use the default alsa channel by default). The HOWTO on dmix is here:

dmix HOWTO on alsa-project.org

This one should work better though and has more explanation:

dmix HOWTO from debian
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nejiron · Posted: Wed Mar 02, 2005 12:02 am Post subject:

got it working, thanks for the help fella's. figured if i brought windows into it id get a speady response :wink:

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wswartzendruber · Posted: Wed Mar 02, 2005 12:07 am Post subject:

I have a CS46XX and I'm able to send multiple streams into it using a kernel option: "Enable Multiple DSP..."
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curtis119 · Posted: Wed Mar 02, 2005 12:29 am Post subject:

Arainach · l33t Joined: 08 Jul 2004 Posts: 609

This should be in the multimedia forums.

What you're talking about is mixing. Most sound cards have hardware Mixing (For instance, every Sound Blaster since the ancient Sound Blaster 1024 does). For instance, my Audigy2 plays about a billion sounds simultaneously no problem. Onboard soundchips like AC97 often don't. You need software mixing via dmix. Look into it in the Multimedia forum.
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curtis119 · Posted: Wed Mar 02, 2005 1:38 am Post subject:

Earthwings · Posted: Wed Mar 02, 2005 9:57 am Post subject:

Moved from OTW.

transient · l33t Joined: 13 Jan 2005 Posts: 759

Even with a chipset having a hardware mixer, its not gonna do anything unless the specs for said mixer are released or someone manages to reverseengineer a solution. Case in point being nForce2 under linux. Supports hardware mixing fine, but as of yet, nVidia are being horribly stingy, so we're limited to either OSS hardware mixing, or using an ALSA plugin such as dmix.
Which to be honest, does almost as good a job. It only requires some more RAM for the IPC stuff.

hvengel · Guru Joined: 19 Sep 2004 Posts: 515

Epyon · l33t Joined: 11 Sep 2003 Posts: 754 Location: NJ, USA

beandog · Posted: Thu Mar 10, 2005 8:52 pm Post subject:

transient · l33t Joined: 13 Jan 2005 Posts: 759

The nforce-audio driver only provides hardware mixing under OSS so far.
Hopefully nVidia will get around to providing ALSA hardware mixing too soon..

beandog · Posted: Thu Mar 10, 2005 11:51 pm Post subject:

Yah, I noticed the "tell nvidia .... " sticky. Right after posting here, of course.

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