In a typical configuration, the live output from the broadcast studio and the scheduled output from the storage archive are mixed together before being sent further along the broadcast chain, such as to a transmitter or streaming media server on the Internet.
If your Airtime server is hosted in a remote data centre, you may not have the option to handover the streaming media source from a live to scheduled show manually, because you have no physical access to connect a broadcast mixer to the server. Alternatively, you may have an Airtime server at the studio, connected to your main mixer, but wish stream handovers to take place automatically at the correct times. Disconnecting the stream and beginning another is less than ideal, because the audience's media players will also be disconnected when that happens.
The Icecast server has a fallback-mount feature which can be used to move clients (media players used by listeners or viewers) from one source to another, as new sources become available. This makes it possible to handover from Airtime scheduled output to a live show from another source, and handover to Airtime again once the live show has ended.
To enable fallback mounts, edit the main Icecast configuration file to define the mount points you will use, and the relationship between them.
$ sudo nano /etc/icecast2/icecast.xml
The example <mount> section provided in the icecast.xml file is commented out by default. Before or after the commented section, add three mount point definitions. The default mount point used by Airtime is /airtime.ogg which is shown in the /etc/airtime/liquidsoap.cfg file. You must also define a mount point for the live source (called /live.ogg in this example) and a mount point for the public to connect to (called /stream.ogg in this example).
<mount> <mount-name>/airtime.ogg</mount-name> <hidden>0</hidden> </mount> <mount> <mount-name>/live.ogg</mount-name> <fallback-mount>/airtime.ogg</fallback-mount> <fallback-override>1</fallback-override> <hidden>0</hidden> </mount> <mount> <mount-name>/stream.ogg</mount-name> <fallback-mount>/live.ogg</fallback-mount> <fallback-override>1</fallback-override> <hidden>0</hidden> </mount>
These mount point definitions mean that a client connecting to a URL such as http://icecast.example.com:8000/stream.ogg will first fall back to the /live.ogg mount point if it is available. If not, the client will fall back in turn to the /airtime.ogg mount point for scheduled show playout.
Setting the value of <fallback-override> to 1 (enabled) means that when the /live.ogg mount point becomes available again, the client will be re-connected to it. If you wish to hide the /airtime.ogg and /live.ogg mount points from the public Icecast web interface, set the value of <hidden> in each of these definitions to 1.
Live source configuration
To integrate the live streaming source with Airtime, connect the live source to the Icecast server with the same parameters defined in the /etc/airtime/liquidsoap.cfg file, except for the mount point. This should be the live mount point you have defined in the /etc/icecast2/icecast.xml file, such as /live.ogg in the example above.
To configure Mixxx for streaming to Icecast, click Options, Preferences, then Live Broadcasting. For server Type, select the default of Icecast 2 when streaming to Debian or Ubuntu servers, as this is the version of Icecast supplied with those GNU/Linux distributions.
By default, Icecast streams are buffered to guard against network problems, which causes latency for remote listeners. When monitoring the stream from a remote location, you may have to begin the live stream a few seconds before the previous stream ends to enable a smooth transition.