Raspberry Pi audio output

[Oleksandr Tymoshenko]

> On Mar 6, 2015, at 12:49 AM, Milan Obuch <freebsd-arm at dino.sk> wrote:
> 
> Hello,
> 
> there is pcm0 device on Raspberry Pi, sysctl dev.pcm shows
> 
> dev.pcm.%parent: 
> dev.pcm.0.%desc: VCHQI audio
> dev.pcm.0.%driver: pcm
> dev.pcm.0.%location: 
> dev.pcm.0.%pnpinfo: 
> dev.pcm.0.%parent: vchiq0
> dev.pcm.0.play.vchans: 1
> dev.pcm.0.play.vchanmode: fixed
> dev.pcm.0.play.vchanrate: 48000
> dev.pcm.0.play.vchanformat: s16le:2.0
> dev.pcm.0.buffersize: 0
> dev.pcm.0.bitperfect: 0
> dev.pcm.0.dest: 0
> 
> In /dev directory, there are just midistat and sndstat devices,
> cat /dev/sndstat shows
> 
> Installed devices:
> pcm0: <VCHQI audio> (play) default
> 
> How can I use this device? I would like to check it and possibly use...
> Also, is it connected to 3.5 mm jack or do we have sound through HDMI?

It’s standard OSS interface, you can either access /dev/dsp0 directly or use
one of audio library (e.g. libao). To test it just install mpg321 and try to 
play some mp3s.

Audio output is connected to both HDMI and 3.5mm jack and controlled
by  dev.pcm.0.dest sysctl. Available values are:

0 - auto. VideoCore decides where to direct audio output based on
    current HDMI mode.
1 - headphones, audio goes to 3.5mm jack
2 - HDMI. Audio goes to HDMI display. Please note that not every HDMI
    mode supports audio.