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!


Returns the current recording source


int route;
ioctl(fd, SNDCTL_DSP_GET_RECSRC, &route);

The above code fragment lacks all error checks for clarity. Real world applications must always check for the errors and handle them as described below. Also most OSS ioctl calls will return information in the argument variable and it's usually necessary to check it too.


This ioctl call returns the currently selected recording source. The returned value is a number between 0 and N. The meaning of the number depends on the device and it's current setup. There are no predefined values. The application needs to use SNDCTL_DSP_GET_RECSRC_NAMES to figure out the currently available recording sources. See the Audio input and output volumes and routings section for more info about the routing mechanism.

Related ioctl calls

Compatibility issues

This ioctl call is new in OSS 4.0 and not supported by the freeware implementations based on older OSS versions. If this call returns errno=EINVAL then the best approach is to assume that the recording source is not selectable. In this situation it's better to ask the user to change the recording source manually rather than trying to use desperate hacks to change the recording source.

Traditionally many audio applications have used the mixer ioctl calls to change the recording source. This must be avoided because in practice no program does this correctly. In addition the only correct way doesn't work with the freeware OSS clones anyway.

Please look at the When OSS audio ioctl calls can be made section for information about DSP ioctl call ordering.

OSS ioctl return values

The return value from the OSS ioctl calls will be -1 if a fatal error occurred. Other values mean that the ioctl call was more or less successful. However in most cases the application must check the value returned in the argument to see what was the accepted value.

Please see the Possible error codes (errno) returned by OSS calls section for more info about the error codes returned by OSS.

Sample programs

ossplay.cSources for the ossplay audio player and for the ossrecord
recsrc.cA sample program for recording source selection

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