Better Linux Sound Managment With ALSA, Part 2 - page 3

Testing Sound Channels

arecord is a recording utility included with ALSA. It's not a mighty mixer recorder with trainloads of features, but a simple utility for making audio recordings in WAV format. You can fine-tune your sampling rate, interrupts intervals, buffer size, sample format, and all manner of finicky settings. Me, I stick with the shortcuts: the -f cd option records in CD format, and -f dat for digital audio. It's great for scripting, and good quick test of your recording and playback:

$ arecord -vv  -D headset -fcd  test.wav
$ aplay -vv -D v8237 test.wav

Hit CTRL +C stop either command.

A couple of random nuggets: run cat /proc/asound/version to get your ALSA version.

The examples are from the onboard sound on my low-budget ECS motherboard. As you can see, it supports digital output (S/PDIF = Sony-Phillips Digital Interface) in addition to analog. However, I can't use it--there is neither connector nor headers on the motherboard. Beware when you are buying sound cards, because they often claim "24-bit digital sound!" or some such. All computer sound cards support digital sound- their main job is converting digital sound files for analog speakers. If you want digital output to digital speakers, read the specs carefully to be sure you're getting real 100% digital.

Resources

• man alsamixer
• man aplay/arecord
• man speaker-test
• HOWTO Dolby Digital and DTS
• ALSA, with lots of helpful documentation
• Unofficial, but very helpful ALSA Wiki

Carla Schroder is the author of the Linux Cookbook and the newly-released Linux Networking Cookbook, and is a regular contributor to LinuxPlanet.