[WIP] implement threaded level meter for input level

Issues:
1. Using 100% processor.
2. Temporary silences an active call -> reactivate after widget hide.

Still greatly improves metering audio data, removing "read buffer" errors.

src/audio/audio.cpp

@@ -34,6 +34,7 @@
 #include <QDebug>
 #include <QFile>
 #include <QMutexLocker>
+#include <QPointer>
 #include <QThread>
 #include <QWaitCondition>
 
@@ -47,6 +48,8 @@
  #include <AL/alc.h>
 #endif
 
+Audio* Audio::instance{nullptr};
+
 class AudioPrivate
 {
 public:
@@ -86,6 +89,8 @@ public:
     Audio::PtrList      outputSubscriptions;
     bool                inputInitialized;
     bool                outputInitialized;
+
+    QPointer<AudioMeter>    mAudioMeter;
 };
 
 /**
@@ -134,7 +139,115 @@ private:
     ALuint      mSource;
 };
 
-Audio* Audio::instance{nullptr};
+class AudioMeter : public QThread
+{
+public:
+    AudioMeter()
+        : mActive(false)
+    {
+        connect(this, &AudioMeter::finished, this, &AudioMeter::deleteLater);
+    }
+
+    void waitForData(QMutex* condition)
+    {
+        mCheckGainChanged.wait(condition);
+    }
+
+    void monitorFrame()
+    {
+        mDoMonitoring.wakeAll();
+    }
+
+private:
+    void run() override final
+    {
+        static const int framesize = AUDIO_FRAME_SAMPLE_COUNT * AUDIO_CHANNELS;
+
+        Audio& audio = Audio::getInstance();
+
+        mNewMaxGain = 0.f;
+        mActive = true;
+
+        while (mActive) {
+            int16_t buff[framesize] = {0};
+            if (audio.tryCaptureSamples(buff, AUDIO_FRAME_SAMPLE_COUNT)) {
+                mMeterLock.lock();
+                mNewMaxGain = 0.f;
+                for (int i = 0; i < framesize; ++i) {
+                    mNewMaxGain = qMax(mNewMaxGain, qAbs(buff[i]) / 32767.0);
+                }
+                mMeterLock.unlock();
+            } else if (mNewMaxGain > 0.f) {
+                mNewMaxGain -= 0.01f;
+            }
+
+            mMeterLock.lock();
+            mCheckGainChanged.wakeAll();
+            mDoMonitoring.wait(&mMeterLock);
+            mMeterLock.unlock();
+        }
+    }
+
+public:
+    QMutex          mMeterLock;
+    QWaitCondition  mDoMonitoring;
+    QWaitCondition  mCheckGainChanged;
+    bool            mActive;
+    qreal           mNewMaxGain;
+};
+
+AudioMeterListener::AudioMeterListener(AudioMeter* measureThread)
+    : mActive(false)
+    , mAudioMeter(measureThread)
+{
+    assert(mAudioMeter);
+}
+
+void AudioMeterListener::start()
+{
+    QThread* listener = new QThread;
+    connect(listener, &QThread::started, this, &AudioMeterListener::doListen);
+    connect(listener, &QThread::finished, listener, &QThread::deleteLater);
+    moveToThread(listener);
+
+    listener->start();
+    mAudioMeter->start();
+}
+
+void AudioMeterListener::stop()
+{
+    mActive = false;
+}
+
+void AudioMeterListener::doListen()
+{
+    mMaxGain = 0.f;
+    mActive = true;
+
+    QMutexLocker locker(&mAudioMeter->mMeterLock);
+    while (mActive) {
+        mAudioMeter->waitForData(locker.mutex());
+
+        locker.unlock();
+        //qDebug() << "GAIN:" << mAudioMeter->mNewMaxGain << "/" << mMaxGain;
+        if (mAudioMeter->mNewMaxGain != mMaxGain) {
+            if (mAudioMeter->mNewMaxGain > mMaxGain)
+            {
+                mMaxGain = mAudioMeter->mNewMaxGain;
+                emit gainChanged(mMaxGain);
+            } else if (mMaxGain > 0.02f) {
+                mMaxGain -= 0.0005f;
+                emit gainChanged(mMaxGain);
+            }
+        }
+        locker.relock();
+
+        mAudioMeter->monitorFrame();
+    }
+
+    mAudioMeter->mActive = false;
+}
+
 
 /**
 Returns the singleton's instance. Will construct on first call.
@@ -149,6 +262,14 @@ Audio& Audio::getInstance()
     return *instance;
 }
 
+AudioMeterListener* Audio::createAudioMeterListener() const
+{
+    if (!d->mAudioMeter)
+        d->mAudioMeter = new AudioMeter;
+
+    return new AudioMeterListener(d->mAudioMeter);
+}
+
 Audio::Audio()
     : d(new AudioPrivate)
 {

src/audio/audio.h

@@ -28,6 +28,8 @@
 
 struct Tox;
 class AudioFilterer;
+class AudioMeter;
+class AudioMeterListener;
 class AudioPrivate;
 
 // Public default audio settings
@@ -49,6 +51,8 @@ public:
 public:
     void startAudioThread();
 
+    AudioMeterListener* createAudioMeterListener() const;
+
     qreal outputVolume();
     void setOutputVolume(qreal volume);
 
@@ -105,4 +109,25 @@ private:
     AudioPrivate* d;
 };
 
+class AudioMeterListener : public QObject
+{
+    Q_OBJECT
+public:
+    explicit AudioMeterListener(AudioMeter* measureThread);
+
+    void start();
+    void stop();
+
+signals:
+    void gainChanged(qreal newMaxGain);
+
+private slots:
+    void doListen();
+
+private:
+    bool            mActive;
+    AudioMeter*     mAudioMeter;
+    qreal           mMaxGain;
+};
+
 #endif // AUDIO_H

src/widget/tool/micfeedbackwidget.cpp

@@ -24,7 +24,6 @@
 
 MicFeedbackWidget::MicFeedbackWidget(QWidget *parent)
     : QWidget(parent)
-    , timerId(0)
 {
     setFixedHeight(20);
 }
@@ -59,41 +58,21 @@ void MicFeedbackWidget::paintEvent(QPaintEvent*)
     }
 }
 
-void MicFeedbackWidget::timerEvent(QTimerEvent*)
-{
-    const int framesize = AUDIO_FRAME_SAMPLE_COUNT * AUDIO_CHANNELS;
-    int16_t buff[framesize] = {0};
-
-    if (Audio::getInstance().tryCaptureSamples(buff, AUDIO_FRAME_SAMPLE_COUNT))
-    {
-        double max = 0;
-
-        for (int i = 0; i < framesize; ++i)
-            max = std::max(max, fabs(buff[i] / 32767.0));
-
-        if (max > current)
-            current = max;
-        else
-            current -= 0.05;
-
-        update();
-    }
-    else if (current > 0)
-    {
-        current -= 0.01;
-    }
-}
-
 void MicFeedbackWidget::showEvent(QShowEvent*)
 {
-    timerId = startTimer(60);
+    mMeterListener = Audio::getInstance().createAudioMeterListener();
+    connect(mMeterListener, &AudioMeterListener::gainChanged, this, &MicFeedbackWidget::onGainMetered);
+    mMeterListener->start();
 }
 
 void MicFeedbackWidget::hideEvent(QHideEvent*)
 {
-    if (timerId != 0)
-    {
-        killTimer(timerId);
-        timerId = 0;
-    }
+    mMeterListener->stop();
+}
+
+void MicFeedbackWidget::onGainMetered(qreal value)
+{
+    current = value;
+    //qDebug("Gain metered at %.3f", current);
+    update();
 }

src/widget/tool/micfeedbackwidget.h

@@ -22,6 +22,8 @@
 
 #include <QWidget>
 
+class AudioMeterListener;
+
 class MicFeedbackWidget : public QWidget
 {
     Q_OBJECT
@@ -30,13 +32,15 @@ public:
 
 protected:
     void paintEvent(QPaintEvent* event) override;
-    void timerEvent(QTimerEvent* event) override;
     void showEvent(QShowEvent* event) override;
     void hideEvent(QHideEvent* event) override;
 
+private slots:
+    void onGainMetered(qreal value);
+
 private:
-    double current;
-    int timerId;
+    qreal current;
+    AudioMeterListener* mMeterListener;
 };
 
 #endif // MICFEEDBACKWIDGET_H