audio: Add a config option for queue buffer size

It may help to increase this for users that are experiencing buffering
before track changes. Workaround for #1409.

docs/changelog.rst

@@ -169,6 +169,10 @@ Audio
   This should be fixed properly together with :issue:`1222`. (Fixes:
   :issue:`1430`, PR: :issue:`1438`)
 
+- Add a new config option, buffer_time, for setting the buffer time of the
+  GStreamer queue. If you experience buffering before track changes, it may
+  help to increase this. Workaround for :issue:`1409`.
+
 Gapless
 -------
 

docs/config.rst

@@ -155,6 +155,16 @@ These are the available audio configurations. For specific use cases, see
     ``gst-inspect-1.0`` to see what output properties can be set on the sink.
     For example: ``gst-inspect-1.0 shout2send``
 
+.. confval:: audio/buffer_time
+
+    Buffer size in milliseconds.
+
+    Expects an integer above 0.
+
+    Sets the buffer size of the GStreamer queue. If you experience buffering
+    before track changes, it may help to increase this. The default is letting
+    GStreamer decide the size.
+
 
 Logging configuration
 =====================

mopidy/audio/actor.py

@@ -470,6 +470,11 @@ class Audio(pykka.ThreadingActor):
         # systems. So leave the default to play it safe.
         queue = Gst.ElementFactory.make('queue')
 
+        if self._config['audio']['buffer_time'] > 0:
+            queue.set_property(
+                'max-size-time',
+                self._config['audio']['buffer_time'] * Gst.MSECOND)
+
         audio_sink.add(queue)
         audio_sink.add(self._outputs)
 

mopidy/config/__init__.py

@@ -38,6 +38,7 @@ _audio_schema['mixer_track'] = Deprecated()
 _audio_schema['mixer_volume'] = Integer(optional=True, minimum=0, maximum=100)
 _audio_schema['output'] = String()
 _audio_schema['visualizer'] = Deprecated()
+_audio_schema['buffer_time'] = Integer(optional=True, minimum=1)
 
 _proxy_schema = ConfigSchema('proxy')
 _proxy_schema['scheme'] = String(optional=True,

mopidy/config/default.conf

@@ -15,6 +15,7 @@ config_file =
 mixer = software
 mixer_volume =
 output = autoaudiosink
+buffer_time =
 
 [proxy]
 scheme =