Add new mopidy.audio.utils functions (fixes #301).

Adds functions to create buffers, calcalute buffer durations based on number of
samples and the sample rate and converting milliseconds to gst internal clock
time.

This also alows for the removal of all gst imports outside of mopidy.audio.

mopidy/audio/__init__.py

@@ -4,3 +4,5 @@ from __future__ import unicode_literals
 from .actor import Audio
 from .listener import AudioListener
 from .constants import PlaybackState
+from .utils import (calculate_duration, create_buffer, millisecond_to_clocktime,
+                    supported_uri_schemes)

mopidy/audio/utils.py

@@ -5,6 +5,33 @@ pygst.require('0.10')
 import gst
 
 
+def calculate_duration(num_samples, sample_rate):
+    """Determine duration of samples using a gst helper for preciese math."""
+    return gst.util_uint64_scale(num_samples, gst.SECOND, sample_rate)
+
+
+def create_buffer(data, capabilites=None, timestamp=None, duration=None):
+    """Create a new gstreamer buffer based on provided data.
+
+    Mainly intended to keep gst imports out of non audio modules.
+    """
+    buffer_ = gst.Buffer(data)
+    if capabilites:
+        if isinstance(capabilites, basestring):
+            capabilites = gst.caps_from_string(capabilites)
+        buffer_.set_caps(capabilites)
+    if timestamp:
+        buffer_.timestamp = timestamp
+    if duration:
+        buffer_.duration = duration
+    return buffer_
+
+
+def millisecond_to_clocktime(value):
+    """Convert a millisecond time to internal gstreamer time."""
+    return value * gst.MSECOND
+
+
 def supported_uri_schemes(uri_schemes):
     """Determine which URIs we can actually support from provided whitelist.
 

mopidy/backends/spotify/playback.py

@@ -1,14 +1,11 @@
 from __future__ import unicode_literals
 
-import pygst
-pygst.require('0.10')
-import gst
-
 import logging
 import functools
 
 from spotify import Link, SpotifyError
 
+from mopidy import audio
 from mopidy.backends import base
 
 
@@ -71,5 +68,6 @@ class SpotifyPlaybackProvider(base.BasePlaybackProvider):
             logger.debug('Skipping seek due to issue #300')
             return
 
-        self.backend.spotify.buffer_timestamp = time_position * gst.MSECOND
+        self.backend.spotify.buffer_timestamp = audio.millisecond_to_clocktime(
+            time_position)
         self.backend.spotify.session.seek(time_position)

mopidy/backends/spotify/session_manager.py

@@ -1,9 +1,5 @@
 from __future__ import unicode_literals
 
-import pygst
-pygst.require('0.10')
-import gst
-
 import logging
 import os
 import threading
@@ -122,12 +118,13 @@ class SpotifySessionManager(process.BaseThread, PyspotifySessionManager):
             'channels': channels,
         }
 
-        buffer_ = gst.Buffer(bytes(frames))
-        buffer_.set_caps(gst.caps_from_string(capabilites))
-        buffer_.timestamp = self.buffer_timestamp
-        buffer_.duration = num_frames * gst.SECOND / sample_rate
+        duration = audio.calculate_duration(num_frames, sample_rate)
+        buffer_ = audio.create_buffer(bytes(frames),
+                                      capabilites=capabilites,
+                                      timestamp=self.buffer_timestamp,
+                                      duration=duration)
 
-        self.buffer_timestamp += buffer_.duration
+        self.buffer_timestamp += duration
 
         if self.audio.emit_data(buffer_).get():
             return num_frames

mopidy/backends/stream/actor.py

@@ -5,8 +5,7 @@ import urlparse
 
 import pykka
 
-from mopidy import settings
-from mopidy.audio import utils
+from mopidy import audio as audio_lib, settings
 from mopidy.backends import base
 from mopidy.models import Track
 
@@ -18,10 +17,11 @@ class StreamBackend(pykka.ThreadingActor, base.Backend):
         super(StreamBackend, self).__init__()
 
         self.library = StreamLibraryProvider(backend=self)
-        self.playback = base.BasePlaybackProvider(audio=audio, backend=self)
+        self.playback = base.BasePlaybackProvider(audio=audio,
+                                                  backend=self)
         self.playlists = None
 
-        self.uri_schemes = utils.supported_uri_schemes(
+        self.uri_schemes = audio_lib.supported_uri_schemes(
             settings.STREAM_PROTOCOLS)