An alternative implementation of audio ducking for Windows build 1498…

…6 and up: Play silence while we expect to be ducked.

Fixes #6684

source/audioDucking.py

@@ -9,6 +9,8 @@
 import time
 import config
 from logHandler import log
+import winVersion
+from silencePlayer import SilencePlayer
 
 def _isDebug():
 	return config.conf["debugLog"]["audioDucking"]
@@ -27,6 +29,7 @@ def __del__(self):
 AUDIODUCKINGMODE_NONE=0
 AUDIODUCKINGMODE_OUTPUTTING=1
 AUDIODUCKINGMODE_ALWAYS=2
+WINVERSION_DYNAMICDUCKING_MIN=14986
 
 audioDuckingModes=[
 	# Translators: An audio ducking mode which specifies how NVDA affects the volume of other applications.
@@ -50,16 +53,25 @@ def __del__(self):
 _duckingRefCountLock = threading.RLock()
 _modeChangeEvent=None
 _lastDuckedTime=0
+_silencePlayer=None
 
 def _setDuckingState(switch):
-	global _lastDuckedTime
+	global _lastDuckedTime, _silencePlayer
 	with _duckingRefCountLock:
 		import gui
 		ATWindow=gui.mainFrame.GetHandle()
 		if switch:
 			oledll.oleacc.AccSetRunningUtilityState(ATWindow,ANRUS_ducking_AUDIO_ACTIVE|ANRUS_ducking_AUDIO_ACTIVE_NODUCK,ANRUS_ducking_AUDIO_ACTIVE|ANRUS_ducking_AUDIO_ACTIVE_NODUCK)
+			# In Certain Windows builds, dynamic audio ducking was introduced  by Microsoft that conflicts with our own audio ducking code.
+			# To force their dynamic ducking back to static ducking, play silence for the entire length we want to be truely ducked for.
+			if winVersion.winVersion.build>=WINVERSION_DYNAMICDUCKING_MIN:
+				if not _silencePlayer:
+					_silencePlayer=SilencePlayer()
+				_silencePlayer.enable()
 			_lastDuckedTime=time.time()
 		else:
+			if _silencePlayer: 
+				_silencePlayer.disable()
 			oledll.oleacc.AccSetRunningUtilityState(ATWindow,ANRUS_ducking_AUDIO_ACTIVE|ANRUS_ducking_AUDIO_ACTIVE_NODUCK,ANRUS_ducking_AUDIO_ACTIVE_NODUCK)
 
 def _ensureDucked():

source/silencePlayer.py

@@ -0,0 +1,46 @@
+import threading
+import nvwave
+import config
+
+class SilencePlayer(threading.Thread):
+	"""
+	Plays silence on the configured audio output device, to aide in audio ducking.
+	Once instantiated, call enable() to start the silence, and disable() to stop.
+	"""
+
+	_sampleRate=22050
+	_bitDepth=16
+	_channels=1
+
+	def __init__(self):
+		# Create silence of about 200 ms in length
+		self._data='\x00'*(self._sampleRate/2)
+		self._wavePlayer=None
+		self._initEvent=threading.Event()
+		self._wakeEvent=threading.Event()
+		super(SilencePlayer,self).__init__()
+		self.daemon=True
+		self.start()
+
+	def run(self):
+		self._initEvent.set()
+		# Keep either waiting on an event, or feeding silence to the audio device
+		while True:
+			if not self._wakeEvent.isSet():
+				# Ensure that the correct audio device is used each time it starts playing silence
+				self._wavePlayer=None
+				self._wakeEvent.wait()
+			if not self._wavePlayer:
+				self._wavePlayer=nvwave.WavePlayer(channels=self._channels, samplesPerSec=self._sampleRate, bitsPerSample=self._bitDepth, outputDevice=config.conf["speech"]["outputDevice"],wantDucking=False)
+			self._wavePlayer.feed(self._data)
+
+	def disable(self):
+		""" Stops playing silence"""
+		if self._wakeEvent.isSet():
+			self._wakeEvent.clear()
+			self._wavePlayer.stop()
+
+	def enable(self):
+		"""Starts playing silence"""
+		if not self._wakeEvent.isSet():
+			self._wakeEvent.set()