Hitchhiker's Guide to Openbsd

13.2 - Playing different kinds of audio
Digitized audio
Lossless audio formats (AU, PCM, WAV, FLAC, TTA)
Some of the lossless audio formats may be played without the need for third party software, provided 
they contain the uncompressed digital samples in chunks of bytes. These formats include Sun audio 
(AU), raw PCM files (without headers), and RIFF WAV. 
OpenBSD comes with 
aucat(1)
, a program for recording and playing uncompressed audio. The 
following example will play a WAV file. 
$ aucat -i filename.wav
aucat(1)
 supports both headerless and WAV audio files with the -i option. aucat also plays Sun audio 
files where the audio data is encoded as 8 kHz monaural mulaw, which is the most common encoding 
for this type of audio file. 
http://www.openbsd.org/faq/faq13.html (4 of 25)9/4/2011 10:02:21 AM

---

13 - Multimedia
It is also possible to play uncompressed audio data by passing it directly to the audio device. To do this, 
you need to know its main parameters: encoding type, number of channels, sample rate, bits per sample. 
If you don't know this, you might find out with the 
file(1)
utility: 
$ file music.au
music.au: Sun/NeXT audio data: 16-bit linear PCM, stereo, 
44100 Hz
$ file music.wav
music.wav: Microsoft RIFF, WAVE audio data, 16 bit, stereo 
44100 Hz
The only remaining things to know about these example files is that they use little-endian byte ordering 
and signed linear quantization. You could figure this out by reading the header with 
hexdump(1)
. If you 
are using a headerless (raw) file, there is no way to know the parameters beforehand. Set the following 
parameters accordingly using 
audioctl(1)
. 
play.encoding=slinear_le
play.rate=44100
play.channels=2
play.precision=16
Next, pass the audio file to the sound device: 
$ cat music.au > /dev/sound
If you applied the correct settings, you should be hearing what you expected. 
Note: Always use 
/dev/sound
, not 
/dev/audio
, if you want the settings you applied with audioctl 
to stay in place. 
There are, of course, other utilities you can use to play these files. Such as XMMS which is available in 
packages and ports and can play numerous other audio formats. 
Apart from the above, there are audio formats which use lossless data compression. Examples are the 
Free Lossless Audio Codec (FLAC) and TTA. The FLAC implementation has been ported to OpenBSD 
and may be found under 
audio/flac
in packages and ports.