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Judul : Perfect sound with OSS version 4
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Perfect sound with OSS version 4

So I just happened to be keeping my eye on some packages being upgraded in Debian on dist-upgrade, and something caught my eye, the package "libasound2-plugins". I wondered what kind of plugins it provided, so I asked APT to show me what it was. Here's what came up:

Package: libasound2-plugins
Priority: optional
Section: libs
Installed-Size: 488
Maintainer: Debian ALSA Maintainers
Architecture: amd64
Source: alsa-plugins
Version: 1.0.19-2
Depends: libasound2 (>> 1.0.18), libc6 (>= 2.2.5), libjack0 (>= 0.116.1), libpulse0 (>= 0.9.14), libsamplerate0
Filename: pool/main/a/alsa-plugins/libasound2-plugins_1.0.19-2_amd64.deb
Size: 119566
MD5sum: 89efb281a3695d8c0f0d3c153ff8041a
SHA1: fdd93b68ec0b8e6de0b67b3437b9f8c86c04b449
SHA256: 7eb5b023373db00ca1b65765720a99654a0b63be741a5f5db2516a8881048aa6
Description: ALSA library additional plugins
This package contains plugins for the ALSA library that are
not included in the main libasound2 package.
.
The following plugins are included, among other:
- a52: S16 to A52 stream converter
- jack: play or capture via JACK
- oss: run native ALSA apps on OSS drivers
- pulse: play or capture via Pulse Audio
- lavcrate, samplerate and speexrate: rate converters
- upmix and vdownmix: convert from/to 2 and 4/6 channel streams
.
ALSA is the Advanced Linux Sound Architecture.
Enhances: libasound2
Homepage: http://www.alsa-project.org/
Tag: devel::library, role::plugin, works-with::audio

Now something jumped out at me, run native ALSA apps on OSS drivers?
If you read my sound article, you know I'm an advocate of OSSv4, since it seems superior where it matters.

So I looked into the documentation for the Debian (as well as Ubuntu) package "libasound2-plugins" on how this ALSA over OSS works exactly.

I edited /etc/asound.conf, and changed it to the following:

pcm.!default {
type oss
device /dev/dsp
}

ctl.!default {
type oss
device /dev/mixer
}

And presto, every ALSA application now started properly outputting sound for me. No more need to always have to fiddle with configurations for each sound layer to use OSS, because the distros don't allow auto config of them.

I could never get flash on 64 bit with sound before, even though each new OSS release says they "fixed it". Now it does work for me.

I tested the following with ALSA:
MPlayer (-ao alsa)
Firefox, flashplugin-nonfree, Homestar Runner
ZSNES (-ad alsa)
bsnes (defaults)

Oh and in case you're wondering, mixing is working perfectly. I tried running four instances of MPlayer, two set to use ALSA, the other two set to output using OSS, and I was able to hear all four at once.

Now it's great to setup each application and sound layer individually to use OSS, so there's less overhead. But just making this one simple change means you don't have to for each application where the distro defaulted to ALSA, or have to suffer incompatibility when a particular application is ALSA only.


Note that depending how you installed OSS and which version, it may have tried forcing ALSA programs to use a buggy ALSA emulation library, which is incomplete, and not bug for bug compatible with the real ALSA. If that happened to you, here's how to use the real ALSA libraries, which are 100% ALSA compatible, as it's 100% the real ALSA.

First check where everything is pointing with the following command ls -la /usr/lib/libasound.*
I get the following:

-rw-r--r-- 1 root root 1858002 2009-03-04 11:09 /usr/lib/libasound.a
-rw-r--r-- 1 root root 840 2009-03-04 11:09 /usr/lib/libasound.la
lrwxrwxrwx 1 root root 18 2009-03-06 03:35 /usr/lib/libasound.so -> libasound.so.2.0.0
lrwxrwxrwx 1 root root 18 2009-03-06 03:35 /usr/lib/libasound.so.2 -> libasound.so.2.0.0
-rw-r--r-- 1 root root 935272 2009-03-04 11:09 /usr/lib/libasound.so.2.0.0

Now as you can see libasound.so and libasound.so.2 both point to libasound.so.2.0.0. The bad emulation is called libsalsa. So if instead of seeing "-> libasound..." you see "-> libsalsa..." there, you'll want to correct the links.

You can correct with the following commands as root:

cd /usr/lib/
rm libasound.so libasound.so.2
ln -s libasound.so.2.0.0 libasound.so
ln -s libasound.so.2.0.0 libasound.so.2

If you're using Ubuntu and don't know how to switch to root, try sudo su prior to the steps above.

If you'd like to try to configure as many applications as possible to use OSS directly to avoid any unneeded overhead, see the documentation here and here which provide a lot of useful information. However if you're happy with your current setup, the hassle to configure each additional application isn't needed as long as you setup ALSA to use OSS.

Enjoy your sound!

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