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Open Sound System OSS 4.x User's Guide

dsp - Open Sound System audio devices

/dev/dsp is the default audio device in the system. It's connected to the main speakers and the primary recording source (such as microphone). The system administrator can set /dev/dsp to be a symbolic link to the desired default device. The ossinfo utility can be used to list the available audio devices in the system.

/dev/dsp_mmap, /dev/dsp_ac3, /dev/dsp_multich and /dev/dsp_spdifout are default audio devices for specific applications such as games or media (DVD) players.

DIRECT ACCESS AUDIO DEVICE FILES

OSS 4.0 (and later) will create audio devices under /dev/oss/<device> directory. For example /dev/oss/sblive0/pcm0 is the first audio device that belongs to the first Sound Blaster Live! or Audigy card in the system. These direct devices are used when an application needs to access specific audio device (instead of the default one).

You can use the ossinfo utility with the -a option to get a list of the available audio devices in the system.

LEGACY AUDIO DEVICE FILES

Traditionally OSS has created device files like /dev/dsp0 to /dev/dspN for each audio device in the system. OSS 4.0 still supports this legacy naming. These files are symbolic links to the actual device files located under /dev/oss. The ossdevlinks utility is used to manage these links and it will be automatically invoked when OSS is started.

COMPATIBILITY

• The /dev/dsp (default() audio device file will be supported by all OSS implementations and versions.
• The special purpose audio default devices (such as /dev/dsp_mmap) are only supported by OSS 4.0 and later.
• The legacy audio device files (such as /dev/dsp1) are supported by all OSS versions and implementations.
• New style audio device files (under /dev/oss) are only supported by OSS 4.0 and later. However some independent OSS implementations may only support the legacy naming even they are otherwise OSS 4.0 compatible.
• /dev/dsp0 doesn't exist in all Linux systems which use /dev/dsp for the same purpose. In such systems /dev/dsp points to the first audio device and /dev/dsp1 to the second.

PROGRAMMING INFORMATION

See the Audio Programming section of the OSS Programmer's Guide ( DSP ) for more info.

OPTIONS

None

FILES

• /dev/dsp Default audio device
• /dev/dsp_mmap Default audio device for applications using mmap
• /dev/dsp_ac3 Default audio device for applications sending Dolby Digital (AC3) audio to an external receiver.
  
• /dev/dsp_multich Default multichannel (4.0-7.1) audio output device
• /dev/dsp_spdifout Default digital audio (S/PDIF) output device
• /dev/oss/&#38;#38;#38;#38;#38;#38;#38;#38;#60;driver&#38;#38;#38;#38;#38;#38;#38;#38;#62;/pcmN Direct access device files for individual audio devices.
  
• /dev/dsp0 to /dev/dspN Legacy style direct access audio device files.

AUTHOR

4Front Technologies