Decouple QAudioDevice buffer size from AFV 20 ms frame size

Different QAudioDevice plugins have different default buffer sizes. In 
order to cope with bigger buffer sizes than the expected 20 ms,
let the buffer be filled and push from it every 20 ms via timer.

src/blackcore/afv/audio/input.cpp

@@ -21,13 +21,23 @@ namespace BlackCore
     {
         namespace Audio
         {
+            AudioInputBuffer::AudioInputBuffer(QObject *parent) :
+                QIODevice(parent)
+            {}
+
             void AudioInputBuffer::start()
             {
-                open(QIODevice::WriteOnly);
+                open(QIODevice::WriteOnly | QIODevice::Unbuffered);
+                m_timerId = startTimer(20, Qt::PreciseTimer);
             }
 
             void AudioInputBuffer::stop()
             {
+                if (m_timerId > 0)
+                {
+                    killTimer(m_timerId);
+                    m_timerId = 0;
+                }
                 close();
             }
 
@@ -43,14 +53,18 @@ namespace BlackCore
             {
                 QByteArray buffer(data, static_cast<int>(len));
                 m_buffer.append(buffer);
+                return len;
+            }
+
+            void AudioInputBuffer::timerEvent(QTimerEvent *event)
+            {
+                Q_UNUSED(event);
                 // 20 ms = 960 samples * 2 bytes = 1920 Bytes
                 if (m_buffer.size() >= 1920)
                 {
                     emit frameAvailable(m_buffer.left(1920));
                     m_buffer.remove(0, 1920);
                 }
-
-                return len;
             }
 
             Input::Input(int sampleRate, QObject *parent) :
@@ -107,11 +121,8 @@ namespace BlackCore
                 }
 
                 m_audioInput.reset(new QAudioInput(inputDevice, inputFormat));
-                // We want 20 ms of buffer size
-                // 20 ms * nSamplesPerSec × nChannels × wBitsPerSample  / 8 x 1000
-                int bufferSize = 20 * inputFormat.sampleRate() * inputFormat.channelCount() * inputFormat.sampleSize() / (8 * 1000);
-                m_audioInput->setBufferSize(bufferSize);
                 m_audioInputBuffer.start();
+
                 m_audioInput->start(&m_audioInputBuffer);
                 connect(&m_audioInputBuffer, &AudioInputBuffer::frameAvailable, this, &Input::audioInDataAvailable);
 
@@ -130,7 +141,7 @@ namespace BlackCore
 
             void Input::audioInDataAvailable(const QByteArray &frame)
             {
-                const QVector<qint16> samples = convertBytesTo16BitPCM(frame);
+                QVector<qint16> samples = convertBytesTo16BitPCM(frame);
 
                 int value = 0;
                 for (qint16 &sample : samples)
@@ -140,9 +151,9 @@ namespace BlackCore
                         value = std::numeric_limits<qint16>::max();
                     if (value < std::numeric_limits<qint16>::min())
                         value = std::numeric_limits<qint16>::min();
-                    samples = static_cast<qint16>(value);
+                    sample = static_cast<qint16>(value);
 
-                    sampleInput = qAbs(sampleInput);
+                    qint16 sampleInput = qAbs(sample);
                     m_maxSampleInput = qMax(qAbs(sampleInput), m_maxSampleInput);
                 }
 
@@ -155,7 +166,7 @@ namespace BlackCore
                 {
                     InputVolumeStreamArgs inputVolumeStreamArgs;
                     qint16 maxInt = std::numeric_limits<qint16>::max();
-                    inputVolumeStreamArgs.PeakRaw = m_maxSampleInput / maxInt;
+                    inputVolumeStreamArgs.PeakRaw = static_cast<float>(m_maxSampleInput) / maxInt;
                     inputVolumeStreamArgs.PeakDB = (float)(20 * std::log10(inputVolumeStreamArgs.PeakRaw));
                     float db = qBound(minDb, inputVolumeStreamArgs.PeakDB, maxDb);
                     float ratio = (db - minDb) / (maxDb - minDb);

src/blackcore/afv/audio/input.h

@@ -32,7 +32,7 @@ namespace BlackCore
                 Q_OBJECT
 
             public:
-                AudioInputBuffer() {}
+                AudioInputBuffer(QObject *parent = nullptr);
 
                 void start();
                 void stop();
@@ -43,9 +43,13 @@ namespace BlackCore
             signals:
                 void frameAvailable(const QByteArray &frame);
 
+            protected:
+                void timerEvent(QTimerEvent *event) override;
+
             private:
                 static constexpr qint64 frameSize = 960;
                 QByteArray m_buffer;
+                int m_timerId = 0;
             };
 
             struct OpusDataAvailableArgs
@@ -97,7 +101,7 @@ namespace BlackCore
                 int m_opusBytesEncoded = 0;
                 double m_volume = 1.0;
                 int m_sampleCount = 0;
-                qint16 m_maxSampleInput = 0;
+                qint16 m_maxSampleInput = 0.0;
 
                 const int c_sampleCountPerEvent = 4800;
                 const float maxDb = 0;