Brain dead simple audio piper with ALSA
This is simply my set up on a Raspberry Pi running Raspbian that allows me to pipe in the audio in from a Griffin iMic USB audio dongle to a USB Harmon Kardon Soundsticks speaker system.
Included is a python script that depends on python-alsasound that does the equivalent of piping audio data from one device to another.
python-alsasound 0.8.2
sudo apt-get install python-dev libasound2-dev
git clone https://github.com/larsimmisch/pyalsaaudio
cd pyalsaaudio
python setup.py build
sudo python setup.py install
cd ~
git clone https://github.com/liquidx/alsa-audio-pipe.git
cd alsa-audio-pipe
./alsa_audio_piper.py --input imic --output soundsticks --floor-noise 0
Replace imic and soundsticks with your device names (see below on setting up audio if you have problems.)
For enabling on Debian/Raspbian Wheezy which uses init.d/rc.d style init scripts, do the following:
sudo cp alsa-audio-pipe /etc/init.d
# Option 1. Install using chkconfig
sudo chkconfig --add alsa-audio-pipe
# Option 2. Install using update-rc.d
sudo update-rc.d alsa-audio-pipe defaults
To start and stop the service
# start the alsa-audio-pipe
sudo service alsa-audio-pipe start
# Stop the alsa-audio-pipe
sudo service alsa-audio-pipe stop
For more modern distributions, like Debian Jessie that uses systemd style.
sudo cp alsa-audio-pipe.service /etc/systemd/system
sudo systemctl daemon-reload
sudo systemctl enable alsa-audio-pipe
sudo systemctl start alsa-audio-pipe
To start and stop the service
# start the alsa-audio-pipe
sudo systemctl start alsa-audio-pipe
# Stop the alsa-audio-pipe
sudo systemctl stop alsa-audio-pipe stop
ALSA just works straight out of the box once you install everything, I made some additional changes to /etc/asound.conf to point to alias the devices to order-independent names:
# This will create an ALSA card named 'soundsticks' that maps to the SoundSticks card's PCM
pcm.soundsticks {
type hw
card "SoundSticks"
device 0
}
# This will create an ALSA card named 'imic' that maps to the Griffin iMic PCM
pcm.imic {
type hw
card "system"
device 0
}
# Default to SoundSticks as the default audio device.
defaults.pcm.!card "SoundSticks"
defaults.ctl.!card "SoundSticks"
Adjust volume
alsamixer
Store and copy volume for next restart
sudo alsactl store
sudo cp /var/lib/alsa/asound.state /etc/asound.state