ossaudio(3) - NetBSD Manual Pages

OSSAUDIO(3)             NetBSD Library Functions Manual            OSSAUDIO(3)


NAME

     ossaudio -- Open Sound System emulation


LIBRARY

     OSS Audio Emulation Library (libossaudio, -lossaudio)


SYNOPSIS

     #include <soundcard.h>


DESCRIPTION

     The ossaudio library provides an emulation of the Open Sound System audio
     interface.

     Use the native audio(4) and mixer(4) interfaces for new programs, and
     this emulation library only for building code written for other operating
     systems.

   Mixer Control Map
     The following table summarizes the mappings from native interface device
     names to OSSv3 mixer controls.

     Native Device Name    OSS Mixer Control
     *.mic                 SOUND_MIXER_MIC
     *.line                SOUND_MIXER_LINE
     *.cd                  SOUND_MIXER_CD
     *.dac                 SOUND_MIXER_PCM
     *.aux                 SOUND_MIXER_LINE1
     *.record              SOUND_MIXER_IMIX
     *.master              SOUND_MIXER_VOLUME
     *.treble              SOUND_MIXER_TREBLE
     *.bass                SOUND_MIXER_BASS
     *.speaker             SOUND_MIXER_SPEAKER
     *.output              SOUND_MIXER_OGAIN
     *.input               SOUND_MIXER_IGAIN
     *.fmsynth             SOUND_MIXER_SYNTH
     *.midi                SOUND_MIXER_SYNTH


COMPATIBILITY

     The ossaudio interface aims to be compatible with the Open Sound System
     version 4, as described in:

     4Front Technologies, OSS 4.x Programmer's Guide,
     http://manuals.opensound.com/developer/, 2007.


SEE ALSO

     ioctl(2), audio(4), midi(4), mixer(4)


HISTORY

     The ossaudio library first appeared in NetBSD 1.3.

     The Open Sound System up to version 3 was originally the preferred API
     for writing audio code under Linux until ALSA became the new default in
     Linux 2.6.  It remains the preferred API in FreeBSD and Solaris, and a
     large body of code exists supporting it.


BUGS

     ·   The emulation is incomplete.  Some less popular features are not emu-
         lated (e.g. sync groups), but the essential ioctls used by the major-
         ity of software are covered.

     ·   NetBSD AUDIO_MIXER_SET control types cannot be accurately represented
         in the OSSv4 mixer API, so are treated as enums.

     ·   Per-stream volume (i.e.  SNDCTL_DSP_SETPLAYVOL) is not currently
         implemented as in OSSv4, and will instead modify the global volume.
         Applications need to provide samples with the appropriate gain.

     ·   Linux, FreeBSD, and Solaris provide /dev/dsp and /dev/mixer devices
         in place of the /dev/audio and /dev/mixer devices this compatibility
         layer must be accessed through on NetBSD.  However, changing this is
         typically trivial when porting programs.

     ·   The emulation only covers ioctl(), there are other differences as
         well.  E.g., on a write that would block in non-blocking mode Linux
         returns EINTR whereas NetBSD 1.3 returns EAGAIN.

     ·   The emulation uses a #define for ioctl() so some obscure programs can
         fail to compile.

NetBSD 10.99                   October 20, 2020                   NetBSD 10.99