Assume minimum volume when no volume update was received within 250ms

Without this timeout the peak volume update, which was received last,
would be used permanently until the next update arrives.
This might only take place when the source produces audio output again.

plugins/base/macro-condition-audio.cpp

@@ -61,26 +61,48 @@ MacroConditionAudio::~MacroConditionAudio()
 	obs_volmeter_destroy(_volmeter);
 }
 
+float MacroConditionAudio::GetVolumePeak()
+{
+	using namespace std::chrono_literals;
+	using namespace std::chrono;
+	static constexpr std::chrono::milliseconds timeout = 250ms;
+
+	// OBS might rarely not update _peak quickly enough when very low
+	// intervals are configured on the General tab.
+	// In that case _peak might be set to negative infinity still, which
+	// will result in unexpected behavior, so we use the previously valid
+	// peak value instead.
+	//
+	// If no volume update was received within a timeout window, however, it
+	// is assumed, that the source no longer produces any audio output and
+	// thus a peak volume value of negative infinity is used.
+
+	float peak;
+
+	std::lock_guard<std::mutex> lock(_peakMutex);
+	auto msPassedSinceLastUpdate = duration_cast<milliseconds>(
+		high_resolution_clock::now() - _lastPeakUpdate);
+	if (_lastPeakUpdate.time_since_epoch().count() != 0 &&
+	    msPassedSinceLastUpdate > timeout) {
+		peak = -std::numeric_limits<float>::infinity();
+	} else {
+		peak = _peakUpdated ? _peak : _previousPeak;
+	}
+
+	_previousPeak = peak;
+	_peak = -std::numeric_limits<float>::infinity();
+	_peakUpdated = false;
+
+	return peak;
+}
+
 bool MacroConditionAudio::CheckOutputCondition()
 {
 	bool ret = false;
 	OBSSourceAutoRelease source =
 		obs_weak_source_get_source(_audioSource.GetSource());
 
-	// OBS might very rarely not update _peak quickly enough when very low
-	// intervals are configured on the General tab.
-	// In that case _peak might be set to negative infinity still, which
-	// will result in unexpected behavior, so we use the previously valid
-	// peak value instead.
-	float peak;
-	{
-		std::lock_guard<std::mutex> lock(_peakMutex);
-		peak = _peakUpdated ? _peak : _previousPeak;
-		_previousPeak = peak;
-		_peak = -std::numeric_limits<float>::infinity();
-		_peakUpdated = false;
-	}
-
+	float peak = GetVolumePeak();
 	double curVolume = _useDb ? peak : DecibelToPercent(peak) * 100;
 
 	switch (_outputCondition) {
@@ -349,6 +371,7 @@ void MacroConditionAudio::SetVolumeLevel(void *data, const float *,
 		}
 	}
 	c->_peakUpdated = true;
+	c->_lastPeakUpdate = std::chrono::high_resolution_clock::now();
 }
 
 void MacroConditionAudio::ResetVolmeter()

plugins/base/macro-condition-audio.hpp

@@ -71,12 +71,14 @@ private:
 	bool CheckMonitor();
 	bool CheckBalance();
 	void SetupTempVars();
+	float GetVolumePeak();
 
 	Type _checkType = Type::OUTPUT_VOLUME;
 	std::mutex _peakMutex;
 	float _peak = -std::numeric_limits<float>::infinity();
 	float _previousPeak = -std::numeric_limits<float>::infinity();
 	bool _peakUpdated = false;
+	std::chrono::high_resolution_clock::time_point _lastPeakUpdate = {};
 	static bool _registered;
 	static const std::string id;
 };