Open Sound System

The Open Sound System (or OSS) is an alternative sound architecture for Unix-like and POSIX-compatible systems. OSS version 3 was the original sound system for Linux, but was superseded by the Advanced Linux Sound Architecture (or ALSA) in 2002 when OSS version 4 became proprietary software. OSSv4 became free software again in 2007 when 4Front Technologies released its source code and provided it under the GPL license.

Comparisons with ALSA

Some advantages and disadvantages compared to using the Advanced Linux Sound Architecture.

OSS Advantages (users)
  • Per-application volume control.
  • Some legacy (i.e. before 2002) cards can have better support.

OSS Advantages (developers)
  • Support for drivers in userspace.
  • Cross-platform (OSS runs on BSDs and Solaris).
  • Smaller and easier to use API.

ALSA advantages over OSS
  • Better support for USB audio devices.
  • Support for Bluetooth audio devices.
  • Support for AC'97 and HD Audio dial-up soft-modems such as Si3055.
  • Better support for MIDI devices.
  • Support for suspend.
  • Better support for jack detection.
  • Better support for modern hardware.
Note:
  • OSS has experimental output support for USB audio devices, but no input.
  • OSS supports MIDI devices with the help of a software synthesizer such as Timidity or FluidSynth.

Installation

Install the ossAUR package or the package with non-free drivers oss-nonfreeAUR. There is also a development version of OSS available with the oss-gitAUR package.

This will install the OSS, run the OSS install script (temporarily disabling the ALSA modules) and install the OSS kernel modules. Since ALSA is enabled by default in the boot scripts, you need to disable it so it does not conflict with OSS. You can do this by blacklisting the soundcore module.

After blacklisting the module, you can enable oss.service to start at boot.

To start using OSS without needing to reboot, check if any ALSA modules are still loaded (ALSA modules start with "snd"):

# lsmod | grep snd

Remove the ALSA modules as follows:

# lsmod | awk ' { print $1 } ' | grep snd | xargs rmmod

Then restart OSS:

# soundoff && soundon

To completely remove ALSA from your system, you can compile a custom kernel and disable ALSA in its configuration. See Gentoo:ALSA#Kernel for the details.

Note: When uninstalling PulseAudio and ALSA, there is more than one package to remove. Search for "pulse" and "alsa" in your installed packages.

In case you are not part of the audio group, add yourself and relogin for the changes to take effect:

# gpasswd -a $USER audio

In case OSS is not able to detect your card when starting it, run:

# ossdetect -v
# soundoff && soundon

Testing
Warning: The default volume is very loud, avoid using earphones and physically lower the volume of your speakers (if possible) before running the test.

Test OSS by running:

$ osstest

You should be able to hear music during the test process. If there is no audio, try to adjust the volume or refer to the #Troubleshooting section.

If you want to hear sounds from more than one application simultaneously, you need vmix, OSS's software mixer.

Check that vmix is enabled by running:

$ ossmix -a | grep -i vmix

You should see a line like vmix0-enable ON|OFF (currently ON). If you do not see any lines beginning with vmix, it probably means that vmix has not been attached to your sound device. To attach vmix, issue the command:

$ vmixctl attach device

where device is your sound device, e.g. .

To avoid having to issue this command manually in the future, you can add it to , as suggested here.

If you get a "Device or resource busy" error, you need to add to /usr/lib/oss/conf/osscore.conf and then reboot.

See which devices are detected by running:

$ ossinfo

You should be able to see your devices listed under Device Objects or Audio Devices. If the device that you want to use is not at the top of one of these sections, you have to edit /usr/lib/oss/etc/installed_drivers and place the driver for your device at the very top. It may be required to restart OSS:

# soundoff && soundon

If this does not work, comment all drivers listed except the ones for your device.

Volume Control Mixer

To control the volume of various devices, mixers levels will need to be set. There are two mixers:

  • ossmix: a command-line mixer, similar to the BSD audio mixer .
  • ossxmix: a GTK-based graphical mixer.

The basic controls look like:

  1. One tab for each sound card
  2. The vmix (virtual mixer) special configurations appear at the top. These include sampling rate and mixer priority.
  3. These are your sound card jack configurations (input and output). Every mixer control that is shown here is provided by your sound card.
  4. Application vmix mixer controls and sound meters. If the application is not actively playing a sound it will be labeled as and when the application is playing the application name will be shown.

Color Definitions

For high definition (HD) audio, will color jack configurations by their pre-defined jack colors:

Color Type Connector
green front channels (stereo output) 3.5mm TRS
black rear channels (stereo output) 3.5mm TRS
grey side channels (stereo output) 3.5mm TRS
gold center and subwoofer (dual output) 3.5mm TRS
blue line level (stereo input) 3.5mm TRS
pink microphone (mono input) 3.5mm TS

Saving Mixer Levels

Mixer levels are saved when you shut off your computer. If you want to save the mixer level immediately, execute as root:

# savemixer
can be used to write mixer levels to a file with the  switch and restore by the  switch.

Other Mixers

Other mixers that have support for OSS:

  • VolWheel — After the installation, set it to autostart as needed, then enable OSS support by right-clicking on the system tray icon, choosing Preferences and then changing:
  • Driver: OSS.
  • Default Channel: vmix0-outvol (find out what channel to use with ossmix).
  • Default Mixer: ossxmix.
  • In the MiniMixer tab (optional), add vmix0-outvol and optionally others.
https://oliwer.net/b/volwheel.html || volwheelAUR

Configuring Applications for OSS

Applications that use GStreamer

If you have problems with applications that use GStreamer for audio, you can try removing and installing the package which is needed by and .

Applications that use OpenAL

By default OpenAL uses ALSA. To change this, simply define the usage of OSS in :

/etc/openal/alsound.conf
drivers=oss

Audacity

If Audacity starts, but it complains that it cannot open the device or simply does not play anything, then you may be using vmix which prevents Audacity from having exclusive access to your sound device. To fix this, before running Audacity, run:

$ ossmix vmix0-enable OFF

You can restore vmix after closing Audacity with:

$ ossmix vmix0-enable ON

Gajim

By default, Gajim uses to play a sound. For OSS you can change it to the equivalent by going to Edit > Preferences > Advanced, opening the Advanced Configuration Editor and modifying the variable accordingly.

MOC

To use MOC with OSS v4.1 you must change to /dev/ossmix in your configuration file (located in ). For issues with the interface try changing the by pressing in (to change to the sofware mixer).

MPD

MPD is configured through or ~/.mpdconf. Check both of these files, looking for something that looks like:

If you find an uncommented (the lines do not begin with #'s) ALSA configuration like the one above, comment all of it out, or delete it, and add the following:

Further configuration might not be necessary for all users. However, if you experience issues (in that MPD does not work properly after it has been restarted), or if you like having specific (i.e. more user-configured, less auto-configured) configuration files, the audio output for OSS can be more specifically configured as follows:

  • First, run:
$ ossinfo | grep /dev/dsp
  • Look for the line that says something similar to . Take note of what your <SOME_CARD_IDENTIFIER> is, and add these lines to your OSS in your MPD configuration file:

See also: Music Player Daemon#System-wide configuration.

MPlayer

If you are using a GUI (SMplayer, GNOME MPlayer, etc.) you can select OSS as the default output in the settings dialogs. If you use MPlayer from the command-line, you should specify the sound output: 

$ mplayer -ao oss /some/file/to/play.mkv

If you do not want to bother typing it over and over again add to your configuration file (at ).

See also: MPlayer#Configuration.

VLC media player

You can select OSS as the default output in the audio settings.

Wine

To set OSS support in Wine start:

$ winecfg

and go to the tab and select the .

See also: Wine#Sound.

Other applications

See also: ossapps.

Tips and tricks

More convenient and precise volume control

The volume lever of ossxmix is very small, making it difficult to finely control the volume.

Run to find the control you want to control (refer to ), this example is codec1.jack.green.front.

Bind the following commands to the keyboard shortcuts of the desktop environment, such as "+", "-" for the keypad

Increase the volume by 1 (the volume can be between 0 and 100):

$ ossmix codec1.jack.green.front +1

Decrease the volume by 1 (The "--" is needed on some systems so that the "-1" will not be mistaken for a parameter.):

$ ossmix -- codec1.jack.green.front -1

Then you can easily control the volume.

Keyboard volume control

An easy way to mute/unmute and increase/decrease the volume is to use the ossvol script.

Download the script and place it at .

Once you installed it, type:

$ ossvol -t

to toggle mute, or:

$ ossvol -h

to see the available commands.

Note: If ossvol gives an error like Bad mixer control name(987) 'vol', you need to edit the script and change the CHANNEL variable to your default channel (usually vmix0-outvol).

If you want to use multimedia keys with , see Extra keyboard keys and make sure they are properly configured. After that you can use, for example, Xbindkeys to bind them to the script. Add the following to your file: and optionally change the multimedia keys with whatever shortcuts you prefer.

Changing the Sample Rate

Changing the output sample rate is not obvious at first. Sample rates can only be changed by root and vmix must be unused by any programs when a change is requested. Before you follow any of these steps, ensure you are going through a receiver/amplifier and using quality speakers and not simply computer speakers. If you are only using computer speakers, do not bother changing anything here as you will not notice a difference.

By default the sample rate is 48000hz. There are several conditions in which you may want to change this. This all depends on your usage patterns. You want the sample rate you are using to match the media you use the most. If your computer has to change the sampling rate of the media to suit the hardware it is likely, though not guaranteed, that you will have a loss in audio quality. This is most noticeable in down sampling (ie. 96000hz → 48000hz). There is an article about this issue in Stereophile which was discussed on Apple's CoreAudio API mailing list if you wish to learn more about this issue.

Some example sample rates:

44100hz
Sample rate of standard Red Book audio CDs.
88000hz
Sample rate of SACD high definition audio discs/downloads. It is rare that your motherboard will support this sample rate.
96000hz
Sample rate of most high definition audio downloads. If your motherboard is an AC'97 motherboard, this is likely to be your highest bitrate.
192000hz
Sample rate of BluRay, and some (very few) high definition downloads. Support for external audio receiver equipment is limited to high end audio. Not all motherboards support this. An example of a motherboard chipset that would support this includes HD Audio.

To check what your sample rate is currently set to, run:

ossmix | grep rate

You are likely to see .

If you do not see a (or , etc.) being outputted, then it probably means that vmix is disabled. In that case, OSS will use the rate requested by the program which uses the device, so this section does not apply. Exception to this are Envy24 (and Envy24HT) cards that have a special setting which has a similar function (see the manpage).

To change your sample rate:

  1. First, make sure your card is able to use the new rate. Run ossinfo -v2 and see if the wanted rate is in the Native sample rates output.
  2. As root, run . Be aware, this will close any program that currently has an open sound channel.
  3. After all programs occupying vmix are terminated, run as root: replacing the rate with your desired sample rate (and if applicable).
  4. Run and check for vmix0-rate <decimal value> (currently 96000) (Read-only) to see if you were successful.
  5. To make the changes permanent add the following to the file:

and make it executable.

Disable virtual mixing and COOKEDMODE to reduce distortion

vmix is a virtual mixer audio that mixes multiple audio streams but can reduce the sound quality. Simply unchecking vmix-things in OSS Mixer GUI does not always work.

Turn off to disable format conversions for all applications and devices.

Edit the following:

Restart your computer (do not simply restart OSS, it may cause errors).

After that you can still control the volume via ossmix or ossxmix.

A simple system tray applet

For those wanting a very lightweight OSS system tray applet see this one.

To install it:

# cp ossvolctl /usr/bin/ossvolctl

or:

# install -Dm755 ossvolctl /usr/bin/ossvolctl

KDE

Create an application launcher file named in you local application launchers directory ( with:

~/.local/share/applications/ossxmix.desktop
[Desktop Entry]
Name=Open Sound System Mixer
GenericName=Audio Mixer
Exec=ossxmix -b
Icon=audio-card
Categories=Application;GTK;AudioVideo;Player;
Terminal=false
Type=Application
Encoding=UTF-8

To have it autostart with your system, add it to the list in System Settings > System Administration > Startup and Shutdown > Autostart.

Gnome

As root create a file with the following content:

Then go to System > Preferences > Start Up Applications and:

  • Click Add, type in the Name field and in Command field then click Add Button.
  • Login and logout to see the changes.

Record sound output from a program

Suspend and Hibernation

OSS does not automatically support suspend, it must be manually stopped prior to suspending or hibernating and restarted afterwards.

OSS provides and soundoff to enable and disable OSS, although they only stop OSS if all processes that use sound are terminated first.

The following script is a rather basic method of automatically unloading OSS prior to suspending and reloading afterwards.

Save the contents of this script (as root) into and make it executable.

An alternative would be to use s2ram for suspending. Just create a suspend script to and make it executable.

 #!/bin/sh

 ## Checking if you are a root or not
 if ! [ -w / ]; then
   echo >&2 "This script must be run as root"
   exit 1
 fi

 s2ram -f

 sleep 2

 systemctl restart oss.service 2>/tmp/oss.txt || echo "OSS restart failed, check /tmp/oss.txt for information"

With this, all your apps should be fine.

Changing the Default Sound Output

When running , the first test passes for the first channel, but not for the stereo or right channel, it sounds distorted/hisses. If this is what your sound is like, then it is set to the wrong output.

*** Scanning sound adapter #-1 ***
/dev/oss/oss_hdaudio0/pcm0 (audio engine 0): HD Audio play front
- Performing audio playback test... 
<left> OK <right> OK <stereo> OK <measured srate 47991.00 Hz (-0.02%)>

The left sounded good, the right and stereo were the distorted ones.

Let the test continue until you get a working output:

/dev/oss/oss_hdaudio0/spdout0 (audio engine 5): HD Audio play spdif-out 
- Performing audio playback test... 
<left> OK <right> OK <stereo> OK <measured srate 47991.00 Hz (-0.02%)>

If this passed the test on all left, right and stereo, proceed to next step.

For the command to change the default output see this OSS wiki article. Change it to what works for you, for example:

# ln -sf /dev/oss/oss_hdaudio0/spdout0 /dev/dsp_multich

For surround sound (4.0-7.1) choose , for only 2 channels, is sufficient. See this for all available devices.

Creative Sound Blaster X-Fi Surround 5.1 SB1090 USB

This information is taken from the 4front-tech forum.

It is surprising to learn that the external card does not work just because of a missing true return value in the function in ossusb_audio.c.

To fix this, a recompile of OSS is necessary, for now.

  • Grab the latest OSS from AUR
https://aur.archlinux.org/cgit/aur.git/tree/?h=oss
  • Extract it
  • into the folder
  • run
  • to src/kernel/drv/oss_usb/ and edit ossusb_audio.c: add a .
    • should look like so:
  • to and edit , search for and remove it, otherwise OSS will not compile.
  • do

Now you must install the package. Remove OSS first if already installed.

ALSA emulation

You can instruct alsa-lib to use OSS as its audio output system. This works as a sort of ALSA emulation.

Note, however, that this method may introduce additional latency in your sound output, and that the emulation is not complete and does not work with all applications. It does not work, for example, with programs that try to detect devices using ALSA.

So, as most applications support OSS directly, use this method only as a last resort.

In the future, more complete methods may be available for emulating ALSA, such as and .

Instructions
  • Edit as follows.
pcm.oss {
   type oss
    device /dev/dsp
}

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

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

ctl.!default {
    type oss
    device /dev/mixer
}
Note: If you do not want to use OSS anymore, do not forget to revert changes in /etc/asound.conf.

Settings for a specific driver

If something is not working, there is a possibility that some of your OSS settings are driver specific or just wrong for your driver.

To solve this:

  • Find out which driver is used
  • Locate configuration file for device in:
# cd /usr/lib/oss/conf/
  • Try changing defaults. There are only few settings, and they are self explanatory

For example, the setting: 

ich_jacksense = 1

in turns on (which is responsible for recognizing plugged headphones and muting the speaker). Other settings for can be found in where you have to change the hdaudio_jacksense variable.

  • Restart the oss.service for changes take effects.

Troubleshooting

Understanding the problem

If you have a HD Audio sound device, it is very likely that you will have to adjust some mixer settings before your sound works.

HD Audio devices are very powerful in the sense that they can contain a lot of small circuits (called widgets) that can be adjusted by software at any time. These controls are exposed to the mixer, and they can be used, for example, to turn the earphone jack into a sound input jack instead of a sound output jack.

However, there are also bad side effects, mainly because the HD Audio standard is more flexible than it perhaps should be, and because the vendors often only care to get their official drivers working.

When using HD Audio devices, you often find disorganized mixer controls, that do not work at all by default, and you are forced to try every mixer control combination possible, until it works.

Solution

Open and try to change every mixer control in the middle area, that contains the sound card specific controls, as explained in the #Volume Control Mixer section.

You will probably want to setup a program to record/play continuously in the background (e.g. for recording or for playing), while changing mixer settings in in the foreground.

  • Raise every volume control slider.
  • In each option box, try to change the selected option, trying all the possible combinations.
  • If you get noise, try to lower and/or mute some volume controls, until you find the source of the noise.
  • Editing , uncommenting and changing to a value from 0-7 can give you more jack options in .
Note: If you modify this file, restart the oss daemon for the changes to take effect.

MMS sound cracking in Totem

If you hear various cracks or strange noises in Totem during playback, you can try using another backend such as FFmpeg. This will not fix the issue that somehow pops up in GStreamer when playing MMS streams but it will give you the option to play it with good sound quality. Playing it in MPlayer is simple:

# mplayer mmsh://yourstreamurl

Microphone playing through output channels

By default, OSS plays back the microphone through the speakers. To disable this in ossxmix find the "Misc" section and uncheck every "input-mix-mute" box.

Add additional HDAudio sound cards support

OSS provides a "generic" codec driver that should be able to parse 99% of all HDAudio codecs.

If the device are not listed in the source file, add them to it, recompile and start the drivers.

To find the device/vendor IDs for device type 403, do the following:

In this example, "Vendor ID" is "8086" and "Device ID" is "a170".

Change 5 lines of code in the source code, taking "the latest source package"(currently "oss-v4.2-build2020-src-gpl.tar.bz2") as an example:

oss-v4.2-build2020-src-gpl/kernel/drv/oss_hdaudio/.devices
oss_hdaudio     pci8086,a170    Intel High Definition Audio (PCH_C)

It is better to modify the existing "Controller" ( in this example), appending a new line of code may fail. It does not matter if it is .

The last line of code is a bit complicated. This example is an ALC1150 sound card chip. The "Vendor_id" of "ALC1150" is "0x10ec0900", you can get it through a search engine, or try the following:

For sound card chips of different manufacturers, different paragraphs need to be modified. In the example, the paragraph of Realtek manufacturer:

oss-v4.2-build2020-src-gpl/kernel/drv/oss_hdaudio/hdaudio_codecids.h
  {0x10ec0889, "ALC889", VF_ALC88X_HACK, (char **) &alc883remap}, 
  {0x10ec0900, "ALC1150", VF_ALC88X_HACK, (char **) &alc883remap}, 
  {0x10ec0899, "ALC899", VF_ALC88X_HACK, (char **) &alc883remap},

It is very important that on the hardware of this example, modifying the second-to-last line works, but modifying the same code on the first-to-last line fails. You will need to try and modify the same code over and over on different lines to work on your hardware.

For example, try on the 4th last line:

 {0x10ec0887, "ALC887", VF_ALC88X_HACK, (char **) &alc883remap}, 
 {0x10ec0900, "ALC1150", VF_ALC88X_HACK, (char **) &alc883remap}, 
 {0x10ec0889, "ALC889", VF_ALC88X_HACK, (char **) &alc883remap}, 
 {0x10ec0892, "ALC892", VF_ALC88X_HACK, (char **) &alc883remap}, 
 {0x10ec0899, "ALC899", VF_ALC88X_HACK, (char **) &alc883remap},
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See also
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