centos-rpm-rotter

CentOS 7 RPM Specfile for Rotter

centos-rpm-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).

Usage

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

Running rotter through systemd

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.

Systemd service unit templates explained

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.

jackd@.service 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.

rotter@.service 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"