Usb audio/midi/mixer driver
The Open Sound System driver for USB Audio and MIDI devices.
The Audio driver supports:
8 or 16 or 32 bits
2, 4, 6 or 8 channel audio.
SPDIF digital output and Input
Volume control and device input mixer
The oss_usb driver supports all MIDI devices that are compatible with the official USB MIDI specification. In addition the driver supports few devices that use their own private protocol (including some Yamaha and Midiman models).
The USB Audio mixer is a new type of mixer that doesn't have the normal volume controls found on AC97 or Legacy SB devices. The USB audio mixer provides control for selecting the Alternate device setting - this usually allows the device to be switched into a Professional audio mode (eg 24bit or 96Khz mode)
Some USB audio devices use a feature called as alternative settings for bandwidth management. Typically such devices have multiple high speed inputs and outputs that may require more bandwidth than provided by the USB bus. The alternative settings feature is used to select between multiple low speed devices or just few high speed devices.
When the device has multiple alternative settings an "altsetting" selector will be visible in the control panel for the device (use ossmix(1) or ossxmix(1) to change it). Alternative setting OFF means that all audio devices are disabled. The other settings provide different combinations of high/medium speed devices. You can use the ossinfo(1) command (ossinfo -a -v3) to find out the devices supported by the currently selected alternative settings and the capabilities of them.
Under Linux it is necessary to run the ossdetect -d and ossdevlinks commands after an USB device has been hot-plugged. Alternatively you can execute soundoff and soundon to reload OSS.
/etc/oss4/conf/oss_usb.conf Device configuration file