I've only discovered this because of an ALSA bug was making my life miserable. That article was written about a month or two before OSS4 (Open Sound System v4) was released under GPL and CDDL. This past January, it was released under BSD as well. Unfortunately for the developer, he does not understand open source very well. He is now reporting that his revenue went significantly down..
OSS4 does not equal to the crap OSS in Linux 2.4 kernels. Even OSS3 != OSS3 in former linux kernels. He was neglecting the open source version in favour of the commercial one. Instead of improving it, someone forked it. And, the fork became popular. Unfortunately, the original author had no interest in working on the fork. So, he only focused on the commercial version. Now, many years later, the commercial version is fully open source. There is no more commercial version.
I've tried it, and I really like it. Music sounds much better than on ALSA. For example, screaming in alternative rock is more legible. It's like enabling "enhance voice" in a phone. It supports higher PCM values without noise.
The mixer (vmix) is capable of 18 channels. It can also do per application volume control (like PulseAudio).
It totally makes sense that OSS gets back into the kernel because it works on almost every UNIX and UNIX-like system (except OS X). ALSA only works on Linux, and according to that article, developers still prefer the OSS API, even on ALSA. However, the ALSA OSS API is lacking according to an ALSA developer. I can confirm that the comment on the ALSA OSS Emulation API working better than the ALSA API. XMMS with ALSA enabled freezes my system. XMMS with OSS enabled on ALSA does not.
It worked without any configuration besides muting some channels to kill the noise.
ossmix and ossxmix are totally unusable because they do not name the channels properly. ossxmix uses 100% CPU if Compiz is enabled. Version 4.1 will fix this.
I had to figure out confused ossxmix.codec1.connector.jack14.jack 54:54 means. Sane names need to be added to the jacks such as "mater, front, input, auxiliary, microphone, etc.."
It's best to use ossxmix (GTK+ mixer) and playing with all the jacks to figure out what each one does.
One interesting control is how OSS4 should behave (Fast, Medium High, Professional, etc.). It's probably a latency control. ossxmix is a demo app on how you can control the mixer from GTK. It needs to be made usable.
If you use Media Player Daemon, VLC, and MPlayer, OSS4 works beautifully. They use OSS directly. Others have problems.
Totem does not play sound. Totem-Xine uses 100% CPU (Xine-UI works with low CPU usage).
In terminal I noticed some output from oss mixer control saying it received bad arguments. OSS4 is backwards compatible with OSS3, but xine-lib may be using the API badly.
The progress bar (seeker) in GStreamer based applications (Rhythmbox, Banshee) does not work if you use vmix, or it may work, but it will be unsure of the length of a song. You will see it constantly adjusting a few seconds up or down. By the middle of the song, the length reporting generally stabilises. You have to enable softoss (the old mixer). vmix and Gstreamer behave very badly. The Gstreamer developer responsible for OSS claims that it does on his system. Though, he is most likely using the trunk version.
You have to apply this patched gstreamer to make volume control in GNOME work.
While the progress bar problem is fixed with softoss, volume control does not work, even with the patched GStreamer. It only works with vmix. System > Preferences > Sound lists nothing under "Default Mixer Tracks".
Sound does not work in KDE4 at all. While Phonon is based on Xine, which has OSS support, it queries HAL, which does not support OSS4 yet. Therefore, it thinks that there is no sound card.
As for KDE 3.5.9. Amarok works, Noatun works, and anything based on MPlayer should work. KMIX does not work. Same in KDE4.
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The Arch Linux wiki has a good article. Read it.
A Ubuntu user has published an install guide as well.
Check Configuring Applications for OSSv4 after you install it.
Overall, I think it's a million times better than ALSA. It's cross platform, and it's stable. It was released a year ago on 15th of March 2007. Since he does not have a marketing department, no one has heard of it.