From: Steinar H. Gunderson <steinar+nageru@gunderson.no>
Date: Sun, 11 Aug 2019 17:28:17 +0000 (+0200)
Subject: Don't reset an ALSA device when the only thing that changes is which channels to... 
X-Git-Url: https://git.sesse.net/?p=nageru;a=commitdiff_plain;h=9768e380472e6ad68c8fc06efde3fa20f18bfc00

Don't reset an ALSA device when the only thing that changes is which channels to pick out.
---

diff --git a/nageru/alsa_pool.cpp b/nageru/alsa_pool.cpp
index c74ed26..4e12bb7 100644
--- a/nageru/alsa_pool.cpp
+++ b/nageru/alsa_pool.cpp
@@ -79,6 +79,16 @@ void ALSAPool::release_device(unsigned index)
 	}
 }
 
+bool ALSAPool::device_is_held(unsigned index)
+{
+	lock_guard<mutex> lock(mu);
+	if (index < devices.size()) {
+		return devices[index].held;
+	} else {
+		return false;
+	}
+}
+
 void ALSAPool::enumerate_devices()
 {
 	// Enumerate all cards.
diff --git a/nageru/alsa_pool.h b/nageru/alsa_pool.h
index 9c1715c..d421019 100644
--- a/nageru/alsa_pool.h
+++ b/nageru/alsa_pool.h
@@ -80,6 +80,7 @@ public:
 
 	void hold_device(unsigned index);
 	void release_device(unsigned index);  // Note: index is allowed to go out of bounds.
+	bool device_is_held(unsigned index);  // Same here.
 
 	// If device is held, start or restart capture. If device is not held,
 	// stop capture if it isn't already.
diff --git a/nageru/audio_mixer.cpp b/nageru/audio_mixer.cpp
index 07d10da..e441aac 100644
--- a/nageru/audio_mixer.cpp
+++ b/nageru/audio_mixer.cpp
@@ -1256,21 +1256,16 @@ void AudioMixer::set_input_mapping_lock_held(const InputMapping &new_input_mappi
 		const DeviceSpec device_spec{InputSourceType::ALSA_INPUT, card_index};
 		AudioDevice *device = find_audio_device(device_spec);
 		double extra_delay_ms = new_extra_delay_ms[device_spec];
-		if (interesting_channels[device_spec].empty()) {
-			alsa_pool.release_device(card_index);
-		} else {
-			alsa_pool.hold_device(card_index);
-		}
 		if (device->interesting_channels != interesting_channels[device_spec]) {
 			device->interesting_channels = interesting_channels[device_spec];
 			device->extra_delay_ms = extra_delay_ms;
-			alsa_pool.reset_device(device_spec.index);
 			reset_resampler_mutex_held(device_spec);
 		} else if (device->extra_delay_ms != extra_delay_ms &&
 		           device->resampling_queue != nullptr) {
 			device->extra_delay_ms = extra_delay_ms;
 			device->resampling_queue->change_expected_delay(get_delay_seconds(extra_delay_ms));
 		}
+		start_or_stop_alsa_capture(device_spec);
 	}
 	for (unsigned card_index = 0; card_index < num_ffmpeg_inputs; ++card_index) {
 		const DeviceSpec device_spec{InputSourceType::FFMPEG_VIDEO_INPUT, card_index};
@@ -1329,4 +1324,20 @@ bool AudioMixer::is_mono(unsigned bus_index)
 	}
 }
 
+void AudioMixer::start_or_stop_alsa_capture(DeviceSpec device_spec)
+{
+	assert(device_spec.type == InputSourceType::ALSA_INPUT);
+	AudioDevice *device = find_audio_device(device_spec);
+	bool previously_held = alsa_pool.device_is_held(device_spec.index);
+	bool should_be_held = !device->interesting_channels.empty();
+	if (should_be_held) {
+		alsa_pool.hold_device(device_spec.index);
+	} else {
+		alsa_pool.release_device(device_spec.index);
+	}
+	if (previously_held != should_be_held) {
+		alsa_pool.reset_device(device_spec.index);
+	}
+}
+
 AudioMixer *global_audio_mixer = nullptr;
diff --git a/nageru/audio_mixer.h b/nageru/audio_mixer.h
index 0beaf10..2b9aa4b 100644
--- a/nageru/audio_mixer.h
+++ b/nageru/audio_mixer.h
@@ -365,6 +365,7 @@ private:
 	void send_audio_level_callback();
 	std::vector<DeviceSpec> get_active_devices() const;
 	void set_input_mapping_lock_held(const InputMapping &input_mapping);
+	void start_or_stop_alsa_capture(DeviceSpec device_spec);
 
 	unsigned num_capture_cards, num_ffmpeg_inputs;