CentOS 7 RPM Specfile for Rotter

CentOS 7 RPM Specfile for Rotter (Recording of Transmission / Audio Logger for JACK) which is part of Radio Bern RaBe's Audio Packages for Enterprise Linux (RaBe APEL).

There is a pre-built binary packages for CentOS 7 available on RaBe APEL package repository, which can be installed as follows:

# Add EPEL repository
yum install epel-release

# Add RaBe APEL repository
curl -o /etc/yum.repos.d/home:radiorabe:audio.repo \
     http://download.opensuse.org/repositories/home:/radiorabe:/audio/CentOS_7/home:radiorabe:audio.repo
 
# Install rotter
yum install rotter

rotter and jackd can be started via the installed systemd service unit template pairs (and therefore support multiple instances).

To create a rotter and jackd instance pair named example and use jackd's ALSA backend, proceed with the following steps:

# The name of the rotter and jackd instance pair
instanceName="example"

# Create a service instance override for running jackd under the rotter
# user/group with the alsa backend
mkdir /etc/systemd/system/jackd@${instanceName}.service.d
cat > /etc/systemd/system/jackd@${instanceName}.service.d/override.conf << "EOF"
[Service]
User=rotter
Group=rotter
SupplementaryGroups=audio

# Jackd startup options
Environment="JACKD_OPTIONS=-d alsa --device hw:0 --capture --inchannels 2"
EOF

# Enable and start the rotter 'example' instance
systemctl enable rotter@${instanceName}.service
systemctl start rotter@${instanceName}.service
systemctl status rotter@${instanceName}.service

# The rotter instance triggered the start of a jackd instance with the same
# instance name
systemctl status jackd@${instanceName}.service

The systemd service will also create the necessary recording root directory located within the rotter instance root directory /var/lib/rotter/. Or in other words, the recordings will be be available at /var/lib/rotter/example in our example.

The included Systemd service unit templates for rotter and jackd correlate with each other and are supposed to be run with the same instance name.

[email protected] is a generic service unit template for starting one ore more headless jackd instances:

• It is a generic jackd service unit template and can be used for other use-cases as well (i.e. it's not limited to the rotter usage)
• It sets the required real-time priorities (LimitRTPRIO=) and maximum locked-in-memory address space (LimitMEMLOCK=)
• It starts jackd with the dummy backend by default.
• The name of the systemd service instance is used as the jack server name (jackd --name <instance>), so use default as the instance name if you would like to use the default jack server.
• The unit waits for the jackd to be up and running with the help of the jack_wait command.
• Start-up overrides of possible interest are User=/Group=, Environment="JACKD_SERVERNAME=%i" and Environment="JACKD_OPTIONS=-d dummy"
• You need to add SupplementaryGroups=audio to your instance override, in case you would like to use jackd's ALSA backend.

[email protected] is a service unit template for starting one ore more rotter instances:

• It depends on a jackd system service instance unit with the same instance name (BindsTo=jackd@%i.service)
• It sets the required real-time priorities (LimitRTPRIO=) and maximum locked-in-memory address space (LimitMEMLOCK=)
• It starts rotter under the rotter system user and group by default
• It conects to a jackd server with the same name as the instance by default
• It stores the recorded audio files below /var/lib/rotter/<instance> by default
• Startup-up overrides of possible interest are Environment="ROTTER_ROOT_DIR=/var/lib/rotter/%i", Environment="ROTTER_OPTIONS=-a -j" and Environment="JACK_DEFAULT_SERVER=%i"