# ICY metadata

ICY metadata is the name for the mechanism used to update metadata in icecast’s source streams. The techniques is primarily intended 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 submitted separately 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.

## Enable/disable ICY metadata updates

You can enable or disable icy metadata update in `output.icecast` by setting the `send_icy_metadata` parameter to `null`, `true` or `false`. The default value is `null` and does the following:

- Set `true` for: mp3, aac, aac+, wav
- Set `false` for any format using the ogg container

In some cases, `liquidsoap` might not be able to detect if ICY metadata need to be enabled, in which case it will ask you to set a `true` or `false` value for this parameter.

## `song` metadata

Most Icecast listeners expect a `song` metadata to be generated. This metadata should combine both artist and title metadata and will be played preferably.

We provide a default implementation that returns `artist` or `title` metadata when only one of these two is available and `$(artist) - $(title)` otherwise.

You can use the `icy_song` parameter to use your own implementation. Returning `null` from that function disables the metadata altogether.

## 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 intended stream.

For instance the following script registers a telnet command name `metadata.update` that can be used to manually update metadata:

As usual, `liquidsoap -h icy.update_metadata` lists all the arguments of the function.