add a short section on transcoding

README.rst

@@ -3,19 +3,19 @@
 autoradio
 =========
 
-The AutoRadio service aims to provide a reliable, fault-tolerant Icecast
-streaming cluster for audio and video. It provides all the necessary
-components to ensure that the traffic from the source to the clients
-is uninterrupted, even in face of high load or server crashes. All
-this, if possible, without any operator intervention.
+The *autoradio* service aims to provide a reliable, fault-tolerant
+Icecast streaming cluster for audio and video. It provides all the
+necessary components to ensure that the traffic from the source to the
+clients is uninterrupted, even in face of high load or server crashes.
+All this, if possible, without any operator intervention.
 
 It is a full-stack service, meaning that it includes its own DNS and
 HTTP servers, for full control of the request flow.
 
-AutoRadio works by using etcd_ to coordinate the various nodes and store
+Autoradio works by using etcd_ to coordinate the various nodes and store
 the global mount configuration. The intended target is a set of
 homogeneous servers (or virtual machines) dedicated to this purpose.
-AutoRadio also needs a dedicated DNS domain (or a delegation for a
+Autoradio also needs a dedicated DNS domain (or a delegation for a
 subdomain).
 
 
@@ -117,7 +117,7 @@ Operation
 ---------
 
 In order to create a new stream (*mount*, in the Icecast terminology),
-assuming you are running AutoRadio on the ``example.com`` domain:
+assuming you are running autoradio on the ``example.com`` domain:
 
 #. On any node, run::
 
@@ -168,6 +168,18 @@ The ``radiod`` and ``redirectord`` daemons can send runtime metrics to
 a *statsd* server (by default on localhost:8125).
 
 
+Transcoding
++++++++++++
+
+It is possible to set up a mount to relay an upstream mount re-encoded
+with different parameters, using the ``radioctl
+create-transcoding-mount`` command. In this case, autoradio will
+automatically start up a process (a liquidsoap_ instance) to perform
+the re-encoding, which will connect as the mount source. A
+master-election protocol is used to ensure that only one such process
+per mount is started in the whole cluster.
+
+
 Testing
 -------
 
@@ -187,3 +199,4 @@ Use ``vagrant ssh`` to inspect them.
 .. _autoca: https://git.autistici.org/ai/autoca
 .. _Vagrant: http://www.vagrantup.com/
 .. _godep: https://github.com/tools/godep
+.. _liquidsoap: http://savonet.sourceforge.net/