Audio levels, recording and playback on Cobra EBX-12 computer
From MobileRobots Research and Academic Customer Support
The mixer can be controlled using the 'aumix' utility. Adjust output on the "Vol" and "PCM" channels. The "Line" channel should be flagged as the recording channel (select "Line" and push the Spacebar set. A red "R" will appear next to the "Line" channel). On VSBC8 computers, adjust input level on the "Rec" channel (*not* "Line" or "Mic"). On Cobra EBX-12 computers, adjust the "IGain" level. Line and Mic levels should be at 0 (these are playback monitors of the recorded sound, usually resulting in echoing or feedback.)
The "play" and "rec" utilities (part of the featureful Sox sound processing toolkit, supplied on Debian by the 'sox' package), or "play-sample" and "sound-recorder", (supplied on Debian by the 'sound-recorder' package), can be used to test levels by recording and playing back WAV files.
It has been observed that occasionally another device with audio capabilities ends up providing the default audio device and mixer (for example, a BTTV video capture card). Symptoms of this problem include no sound output on the normal audio hardware, even if there are no errors playing it, or unexpected mixer controls (e.g. no "Vol", "PCM", "Mic", but instead seeing just "Line1", "Line2", etc.). This can happen if the kernel module for the other device loads before the driver module for the real computer audio device. You can force the computer audio module to load before, e.g. bttv, by adding the following line to /etc/modules.conf for the i810_audio device on the Versalogic Cobra EBX-12:
above bttv i810_audio
Or on the VSBC8:
above bttv cs4281
This puts i810_audio or cs4281 "above" bttv in the list of modules loaded at boot.
- Audio/Sound Switch and Amplifier
- Microphones for Peoplebot and Pioneer Audio Systems
- Linux Audio Drivers