OpenOB System Basics¶

OpenOB systems are made up of two or three computers. These are the transmitter, a receiver, and configuration server. Typically the configuration server is also installed on the receiver, but this is not always the case, and many OpenOB links (comprised of a transmitter and receiver pair) can share one configuration server.

Installing Prerequisites¶

OpenOB relies on the GStreamer media framework for the underlying audio transport elements.

Additionally, OpenOB needs some Python extensions, and on the configuration server, we must also install the Redis server used for configuration management.

On Debian you can install the prerequisites with the following command:

sudo apt-get install python-gst0.10 python-setuptools gstreamer0.10-plugins-base gstreamer0.10-plugins-bad gstreamer0.10-plugins-good gstreamer0.10-plugins-ugly gstreamer0.10-ffmpeg gstreamer0.10-tools python-gobject python-gobject-2 gstreamer0.10-alsa python-argparse

This should also work on Ubuntu. Your GStreamer implementation must be recent enough to support Opus; this is supported in Ubuntu 13.04 and Debian Wheezy or newer. In order to ensure compatibility, it is recommended that both ends of the link use the same version of GStreamer, which is most easily achieved by running the same operating system version on each end and installing the distribution’s packages as detailed above.

On one machine, which for this tutorial we’ll assume is also our receiver, we’ll install Redis:

[user@rx-host] $ sudo apt-get install redis-server

We also need to make sure Redis binds itself to be accessible to remote machines, not just localhost. You can edit /etc/redis/redis.conf yourself or run the following to instantly make this adjustment

[user@rx-host] $ sudo sed -i.bak ‘s/bind 127.*/bind 0.0.0.0/’ /etc/redis/redis.conf && sudo service redis restart

Installing OpenOB¶

Now we can install OpenOB itself. You can install from git for the bleeding edge, but package releases are tested and stable, and easily installed:

sudo easy_install OpenOB

Networking¶

Make sure you know the IP addresses of each machine and make sure there is no firewall between them. If there is a firewall in place, refer to Firewall Configuration to ensure it is configured properly.

Audio testing¶

You should plug in an audio source to the microphone input of your transmitter - I recommend a music player of some sort for testing - and some speakers or headphones to the output of your receiver. Make sure these work before you proceed.

Setting up a link¶

It’s time to send some audio. The default settings will be fine to start with, so we’ll set up a simple link.

Let’s assume your receiver is also your config server, and has the IP address 192.168.0.10. The transmitter’s address does not matter.

First we’ll start the receiver.

[user@rx-host] $ openob 192.168.0.10 test-rx-node test-link rx

Note the test-link name for the link. This is to differentiate between multiple links between hosts. The IP address we’re giving is for the configuration host, and the ‘rx’ string says this is a receiver. The test-rx-node name is the node name, which identifies this computer.

The receiver will flail around and complain that it can’t configure itself. This is expected!

Now let’s start the transmitter.

[user@tx-host] $ openob 192.168.0.10 test-tx-node test-link tx 192.168.0.10

We’re passing this the same arguments as the receiver, but asking it to be a transmitter instead, and providing the target destination IP address (which since we’re using the receiver as our configuration server, is the same as the configuration server’s address).

This will start up and send some configuration information to the configuration server. When the receiver next checks for configuration (in a second or two) it will start up with the parameters sent by the transmitter, and you should start hearing audio from the receiver’s sound card.

To close the link, just Control-c both ends to send a kill signal.

Further Usage¶

OpenOB has many options on the command line. To find out about them, run openob -h, or openob your-config-host node-name link-name tx -h to find out about tx/rx specific options.