# Audio Backends

Quod Libet currently supports GStreamer and Xine as an audio backend. The default backend can be changed in `~/.quodlibet/config` by setting the `backend` option (`gstbe` = GStreamer, `xinebe` = Xine, `nullbe` = no backend). Make sure Quod Libet isn’t running while you edit the file.

## GStreamer Backend

### JACK support

Quod Libet now supports JACK via Gstreamer’s `jackaudiosink`, if available. To select this, check the Use JACK for playback if available button in the Player tab of Preferences. There’s also an option to auto-connect (wire up) the Quod Libet output to JACK output sinks (e.g. system devices) or not.

### Custom Pipelines

It’s possible to attach a custom GStreamer pipeline to the player backend under File → Preferences → Playback → Output Pipeline. The pipeline syntax is equivalent to what is used in the gst-launch utility. See `man gst-launch` for further information and examples.

In case the custom pipeline doesn’t contain an audio sink, Quod Libet will add a default one for you.

### Debugging Pipelines

In case you are interested in which GStreamer elements and audio formats are used in the current pipeline, start Quod Libet in debug mode (`quodlibet --debug`), go to File → Preferences → Playback and press the Print Pipeline button. It will print the whole pipeline used for the current active song to stdout.

For debugging GStreamer related issues see the official GStreamer docs: Running and debugging GStreamer Applications

### Gapless Playback

Gstreamer supports gapless playback for all common formats except MP3. See the following bug report for more information: https://bugzilla.gnome.org/show_bug.cgi?id=620323

### Selecting an Output Device

If you want QL to output to a different device you have to pass the device option to the sink by setting a custom pipeline. In case of pulseaudio you can get a list of available devices by executing:

    #!/usr/bin/env python2
    import gi
    gi.require_version("Gst", "1.0")
    from gi.repository import Gst

    Gst.init(None)
    dm = Gst.DeviceMonitor()
    dm.start()
    for device in dm.get_devices():
        if device.get_device_class() == "Audio/Sink":
            props = device.get_properties()
            element = device.create_element(None)
            type_name = element.get_factory().get_name()
            device_name = element.props.device
            print "%s device=%r" % (type_name, device_name)
    dm.stop()

which should give you something like:

    pulsesink device='alsa_output.pci-0000_00_1b.0.analog-stereo'

which you can use as is, as a custom pipeline.

## Xine Backend

The Xine backend needs either xine-lib 1.1.x or xine-lib 1.2.x. Since most distributions make QL only depend on GStreamer, you might have to install xine-lib manually (libxine1, lixine2 in Debian/Ubuntu).

To enable the backend, set the `backend` option in the `config` file to `"xinebe"` while QL isn’t running.