audio: Add ReplayGain support to the Gst.Playbin

And add functions for setting and quering the state.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/audio/__init__.py

@@ -2,6 +2,7 @@
 """A custom GObject managing a GStreamer playbin."""
 from gi.repository import GObject
 from gi.repository import Gst
+from . import replaygain
 
 
 class Player(GObject.GObject):
@@ -12,17 +13,29 @@ class Player(GObject.GObject):
     def __init__(self):
         """Initialize the audio Player."""
         super().__init__()
+        self._replaygain = replaygain.Filter()
+
         self._playbin = Gst.ElementFactory.make("playbin")
+        self._playbin.set_property("audio-filter", self._replaygain)
         self._playbin.set_property("video-sink",
                                    Gst.ElementFactory.make("fakesink"))
         self._playbin.set_state(Gst.State.READY)
 
         self.bind_property("volume", self._playbin, "volume")
 
+    def get_replaygain(self) -> tuple[bool, str | None]:
+        """Get the current ReplayGain mode."""
+        mode = self._replaygain.mode
+        return (False, None) if mode == "disabled" else (True, mode)
+
     def get_state(self) -> Gst.State:
         """Get the current state of the Player."""
         return self._playbin.get_state(Gst.CLOCK_TIME_NONE).state
 
+    def set_replaygain(self, enabled: bool, mode: str) -> None:
+        """Set the ReplayGain mode."""
+        self._replaygain.mode = mode if enabled else "disabled"
+
     def shutdown(self) -> None:
         """Shut down the player."""
         self._playbin.set_state(Gst.State.NULL)

tests/audio/test_audio.py

@@ -1,6 +1,8 @@
 # Copyright 2022 (c) Anna Schumaker.
 """Tests our GObject audio player wrapping a GStreamer Playbin element."""
+import io
 import unittest
+import unittest.mock
 import emmental.audio
 from gi.repository import GObject
 from gi.repository import Gst
@@ -36,6 +38,29 @@ class TestAudio(unittest.TestCase):
         self.assertEqual(self.player.volume, 0.5)
         self.assertEqual(self.player._playbin.get_property("volume"), 0.5)
 
+    @unittest.mock.patch("sys.stdout", new_callable=io.StringIO)
+    def test_replaygain(self, mock_stdout: io.StringIO):
+        """Test that ReplayGain functions work as expected."""
+        self.assertIsInstance(self.player._replaygain,
+                              emmental.audio.replaygain.Filter)
+        self.assertEqual(self.player._playbin.get_property("audio-filter"),
+                         self.player._replaygain)
+
+        self.assertEqual(self.player._replaygain.mode, "disabled")
+        self.assertEqual(self.player.get_replaygain(), (False, None))
+
+        self.player.set_replaygain(True, "album")
+        self.assertEqual(self.player._replaygain.mode, "album")
+        self.assertEqual(self.player.get_replaygain(), (True, "album"))
+        self.assertRegex(mock_stdout.getvalue(),
+                         r"audio: setting ReplayGain mode to 'album'")
+
+        self.player.set_replaygain(False, "track")
+        self.assertEqual(self.player._replaygain.mode, "disabled")
+        self.assertEqual(self.player.get_replaygain(), (False, None))
+        self.assertRegex(mock_stdout.getvalue(),
+                         r"audio: setting ReplayGain mode to 'disabled'")
+
     def test_shutdown(self):
         """Test that the shutdown function works as expected."""
         self.player.shutdown()