Fix #78. Add Context suspend and resume. Verified CPU utilization is …

…minimized upon suspension

include/LabSound/core/AudioContext.h

@@ -160,6 +160,12 @@ class AudioContext
     void startOfflineRendering();
     std::function<void()> offlineRenderCompleteCallback;
 
+    // suspend the progression of time in the audio context, any queued samples will play
+    void suspend();
+
+    // if the context was suspended, resume the progression of time and processing in the audio context
+    void resume();
+
     // event dispatching will be called automatically, depending on constructor
     // argument. If not automatically dispatching, it is the user's responsibility
     // to call dispatchEvents often enough to satisfy the user's needs.

include/LabSound/core/AudioDevice.h

@@ -83,6 +83,7 @@ class AudioDeviceRenderCallback
     virtual void render(AudioBus * src, AudioBus * dst, int frames, const SamplingInfo & info) = 0;
     virtual void start() = 0;
     virtual void stop() = 0;
+    virtual bool isRunning() const = 0;
 
     virtual const SamplingInfo getSamplingInfo() const = 0;
     virtual const AudioStreamConfig getOutputConfig() const = 0;
@@ -114,6 +115,7 @@ class AudioDevice
     virtual ~AudioDevice() {}
     virtual void start() = 0;
     virtual void stop() = 0;
+    virtual bool isRunning() = 0;
 };
 
 }  // lab

include/LabSound/core/AudioHardwareDeviceNode.h

@@ -51,6 +51,7 @@ class AudioHardwareDeviceNode : public AudioNode, public AudioDeviceRenderCallba
     virtual void render(AudioBus * src, AudioBus * dst, int frames, const SamplingInfo & info) override;
     virtual void start() override;
     virtual void stop() override;
+    virtual bool isRunning() const override;
     virtual const SamplingInfo getSamplingInfo() const override;
     virtual const AudioStreamConfig getOutputConfig() const override;
     virtual const AudioStreamConfig getInputConfig() const override;

include/LabSound/core/NullDeviceNode.h

@@ -58,6 +58,7 @@ class NullDeviceNode final : public AudioNode, public AudioDeviceRenderCallback
     virtual void render(AudioBus * src, AudioBus * dst, int frames, const SamplingInfo & info) override final;
     virtual void start() override final;
     virtual void stop() override final;
+    virtual bool isRunning() const override final;
     virtual const SamplingInfo getSamplingInfo() const override final;
     virtual const AudioStreamConfig getOutputConfig() const override final;
     virtual const AudioStreamConfig getInputConfig() const override final;

src/backends/RtAudio/AudioDevice_RtAudio.cpp

@@ -155,6 +155,8 @@ AudioDevice_RtAudio::AudioDevice_RtAudio(AudioDeviceRenderCallback & callback,
     // heap corruption, for example, when dac.stopStream() is invoked.
     uint32_t bufferFrames = AudioNode::ProcessingSizeInFrames;
 
+    samplingInfo.epoch[0] = samplingInfo.epoch[1] = std::chrono::high_resolution_clock::now();
+
     try
     {
         rtaudio_ctx.openStream(&outputParams, (inputParams.nChannels > 0) ? &inputParams : nullptr, RTAUDIO_FLOAT32,
@@ -177,7 +179,6 @@ AudioDevice_RtAudio::~AudioDevice_RtAudio()
 void AudioDevice_RtAudio::start()
 {
     ASSERT(authoritativeDeviceSampleRateAtRuntime != 0.f);  // something went very wrong
-    samplingInfo.epoch[0] = samplingInfo.epoch[1] = std::chrono::high_resolution_clock::now();
     try
     {
         rtaudio_ctx.startStream();
@@ -198,9 +199,22 @@ void AudioDevice_RtAudio::stop()
     {
         LOG_ERROR(e.getMessage().c_str());
     }
-    samplingInfo = {};
 }
 
+bool AudioDevice_RtAudio::isRunning()
+{
+    try
+    {
+        return rtaudio_ctx.isStreamRunning();
+    }
+    catch (const RtAudioError & e)
+    {
+        LOG_ERROR(e.getMessage().c_str());
+        return false;
+    }
+}
+
+
 // Pulls on our provider to get rendered audio stream.
 void AudioDevice_RtAudio::render(int numberOfFrames, void * outputBuffer, void * inputBuffer)
 {

src/backends/RtAudio/AudioDevice_RtAudio.h

@@ -38,6 +38,7 @@ class AudioDevice_RtAudio : public AudioDevice
     void render(int numberOfFrames, void * outputBuffer, void * inputBuffer);
     virtual void start() override final;
     virtual void stop() override final;
+    virtual bool isRunning() override final;
 };
 
 int rt_audio_callback(void * outputBuffer, void * inputBuffer, unsigned int nBufferFrames, double streamTime, RtAudioStreamStatus status, void * userData);

src/backends/miniaudio/AudioDevice_Miniaudio.cpp

@@ -210,6 +210,8 @@ AudioDevice_Miniaudio::AudioDevice_Miniaudio(AudioDeviceRenderCallback & callbac
 
     authoritativeDeviceSampleRateAtRuntime = outputConfig.desired_samplerate;
 
+    samplingInfo.epoch[0] = samplingInfo.epoch[1] = std::chrono::high_resolution_clock::now();
+
     _ring = new cinder::RingBufferT<float>();
     _ring->resize(static_cast<int>(authoritativeDeviceSampleRateAtRuntime));  // ad hoc. hold one second
     _scratch = reinterpret_cast<float *>(malloc(sizeof(float) * kRenderQuantum * inputConfig.desired_channels));
@@ -230,7 +232,6 @@ AudioDevice_Miniaudio::~AudioDevice_Miniaudio()
 void AudioDevice_Miniaudio::start()
 {
     ASSERT(authoritativeDeviceSampleRateAtRuntime != 0.f);  // something went very wrong
-    samplingInfo.epoch[0] = samplingInfo.epoch[1] = std::chrono::high_resolution_clock::now();
     if (ma_device_start(&_device) != MA_SUCCESS)
     {
         LOG_ERROR("Unable to start audio device");
@@ -243,9 +244,14 @@ void AudioDevice_Miniaudio::stop()
     {
         LOG_ERROR("Unable to stop audio device");
     }
-    samplingInfo = {};
 }
 
+bool AudioDevice_MiniAudio::isRunning()
+{
+    return ma_device_is_started(&_device);
+}
+
+
 // Pulls on our provider to get rendered audio stream.
 void AudioDevice_Miniaudio::render(int numberOfFrames_, void * outputBuffer, void * inputBuffer)
 {

src/core/AudioContext.cpp

@@ -358,6 +358,11 @@ void AudioContext::handlePostRenderTasks(ContextRenderLock & r)
 void AudioContext::synchronizeConnections(int timeOut_ms)
 {
     cv.notify_all();
+
+    // don't synch if the context is suspended as that will simply max out the timeout
+    if (!device_callback->isRunning())
+        return;
+
     while (m_internal->pendingNodeConnections.size_approx() > 0 && timeOut_ms > 0)
     {
         std::this_thread::sleep_for(std::chrono::milliseconds(5));
@@ -651,4 +656,16 @@ void AudioContext::startOfflineRendering()
     device_callback->start();
 }
 
+void AudioContext::suspend()
+{
+    device_callback->stop();
+}
+
+// if the context was suspended, resume the progression of time and processing in the audio context
+void AudioContext::resume()
+{
+    device_callback->start();
+}
+
+
 }  // End namespace lab

src/core/AudioHardwareDeviceNode.cpp

@@ -110,6 +110,11 @@ void AudioHardwareDeviceNode::stop()
     m_platformAudioDevice->stop();
 }
 
+bool AudioHardwareDeviceNode::isRunning() const
+{
+    return m_platformAudioDevice->isRunning();
+}
+
 const SamplingInfo AudioHardwareDeviceNode::getSamplingInfo() const
 {
     return last_info;

src/core/NullDeviceNode.cpp

@@ -107,7 +107,11 @@ void NullDeviceNode::start()
 void NullDeviceNode::stop()
 {
     shouldExit = true;
-    info = {};
+}
+
+bool NullDeviceNode::isRunning() const
+{
+    return m_startedRendering;
 }
 
 void NullDeviceNode::render(AudioBus * src, AudioBus * dst, int frames, const SamplingInfo & info)