Open Sound System
OSS 4.x Programmer's Guide

Do you have problems with sound/audio application development? Don't panic! Click here for help!

Audio device capabilities

Audio device capabilities can be checked using the SNDCTL_AUDIOINFO or SNDCTL_DSP_GETCAPS ioctl calls.

Note that normal applications don't need to care about the device capabilities. This information is more or less provided there just for completeness of the API. OSS is designed to work in uniform manner regardless of the capabilities that are missing. In most cases applications will work better if they don't look at the capabilities at all.

Applications should not refuse to work if certain capabilities are missing. This is simply not acceptable becaise it usually prevents the application from starting without any good reason. The only exceptions are the PCM_CAP_MMAP and PCM_CAP_TRIGGER capabilities that are needed by applications that use mmap.

DSP_CH_MASKPreferred channel configuration
PCM_CAP_ADMASKAudio interface type (digital and/or analog)
PCM_CAP_BATCHThe device may have some extra latencies
PCM_CAP_BINDThe device supports the old output binding calls (obsolete)
PCM_CAP_COPROCThe device has some additional coprocessor (obsolete)
PCM_CAP_DEFAULTDefault device
PCM_CAP_DUPLEXThe device supports the one-device duplex mode
PCM_CAP_FREERATEThe device supports nonstandard sampling rates
PCM_CAP_HIDDENDevice is hidden
PCM_CAP_INPUTThe device can be used for recording
PCM_CAP_MMAPThe device supports mmap
PCM_CAP_MODEMThe device is a modem device (reserved)
PCM_CAP_MULTIThe device can be opened by multiple applications.
PCM_CAP_OUTPUTThe device can be used for playback
PCM_CAP_REALTIMEThe device supports high precision latency control
PCM_CAP_REVISIONCapability interface revision
PCM_CAP_SHADOWObsolete capability
PCM_CAP_SPECIALThe device is for special use
PCM_CAP_TRIGGERThe device supports triggering
PCM_CAP_VIRTUALThe device is virtual (doesn't control hardware directly)

Copyright (C) 4Front Technologies, 2007. All rights reserved.
Back to index OSS web site