title: ICY metadata

h3. ICY metadata

_ICY metadata_ is the name for the mechanism used to update
metadata in Icecast's source streams.
The techniques is primaly intented for data formats that do not support in-stream
metadata, such as mp3 or AAC. However, it appears that Icecast also supports
ICY metadata update for ogg/vorbis streams.

When using the ICY metadata update mechanism, new metadata are submited seperatly from
the stream's data, via a http GET request. The format of the request depends on the
protocol you are using (ICY for shoutcast and icecast 1 or HTTP for icecast 2).

Starting with 1.0, you can do several interesting things with icy metadata updates
in liquidsoap. We list some of those here.

h4. Enable/disable ICY metadata updates

You can enable or disable icy metadata update in @output.icecast@
by setting the @icy_metadata@ parameter to either @"true"@
or @"false"@. The default value is @"guess"@ and does the following:
* Set @"true"@ for: mp3, aac, aac+, wav
* Set @"false"@ for any format using the ogg container

You may, for instance, enable icy metadata update for ogg/vorbis
streams.

h4. Update metadata manually

The function @icy.update_metadata@ implements a manual metadata update
using the ICY mechanism. It can be used independently from the @icy_metadata@
parameter described above, provided icecast supports ICY metadata for the intented stream.

For instance the following script registers a telnet command name @metadata.update@ 
that can be used to manually update metadata:
%%(icy_update_via_telnet.liq)
def icy_update(v) =
  # Parse the argument
  l = string.split(separator=",",v)
  def split(l,v) =
    v = string.split(separator="=",v)
    if list.length(v) >= 2 then
      list.append(l,[(list.nth(v,0),list.nth(v,1))])
    else
      l
    end
  end
  meta = list.fold(split,[],l)

  # Update metadata
  icy.update_metadata(mount="/mystream",password="hackme",
                      host="myserver.net",meta)
  "Done !"
end

server.register("update",namespace="metadata",
                 description="Update metadata",
                 usage="update title=foo,album=bar,..",
                 icy_update)
%%

As ususal, @liquidsoap -h icy.update_metadata@ lists all the arguments
of the function.

