reduced CPU loading in Qt Multimedia output module (patch by Ivan Ponomarev)

git-svn-id: http://svn.code.sf.net/p/qmmp-dev/code/trunk/qmmp@5759 90c681e8-e032-0410-971d-27865f9a5e38

2 files changed, 18 insertions, 2 deletions

diff --git a/src/plugins/Output/qtmultimedia/outputqtmultimedia.cpp b/src/plugins/Output/qtmultimedia/outputqtmultimedia.cpp
index 142292bdd..1f39ecc60 100644
--- a/src/plugins/Output/qtmultimedia/outputqtmultimedia.cpp
+++ b/src/plugins/Output/qtmultimedia/outputqtmultimedia.cpp
@@ -23,12 +23,12 @@
 #include <QAudioOutput>
 #include <QAudioFormat>
 #include <QAudioDeviceInfo>
-#include <QBuffer>
 #include <QSettings>
 #include <QDebug>
+#include <unistd.h>
 
 
-OutputQtMultimedia::OutputQtMultimedia() : Output(), m_buffer(NULL)
+OutputQtMultimedia::OutputQtMultimedia() : Output(), m_buffer(NULL), m_bytes_per_second(0)
 {
 }
 
@@ -44,19 +44,27 @@ bool OutputQtMultimedia::initialize(quint32 freq, ChannelMap map, Qmmp::AudioFor
 	qformat.setByteOrder(QAudioFormat::LittleEndian);
 	qformat.setChannels(map.size());
 	qformat.setSampleType(QAudioFormat::SignedInt);
+
+	//Size of sample representation in input data. For 24-bit is 4, high byte is ignored.
+	qint64 bytes_per_sample = 0;
+
 	switch (format)
 	{
 	case Qmmp::PCM_S8:
 		qformat.setSampleSize(8);
+		bytes_per_sample = 1;
 		break;
 	case Qmmp::PCM_S16LE:
 		qformat.setSampleSize(16);
+		bytes_per_sample = 2;
 		break;
 	case Qmmp::PCM_S24LE:
 		qformat.setSampleSize(24);
+		bytes_per_sample = 4;
 		break;
 	case Qmmp::PCM_S32LE:
 		qformat.setSampleSize(32);
+		bytes_per_sample = 4;
 		break;
 	default:
 		break;
@@ -65,6 +73,8 @@ bool OutputQtMultimedia::initialize(quint32 freq, ChannelMap map, Qmmp::AudioFor
 	if (!qformat.isValid())
 		return false;
 
+	m_bytes_per_second = bytes_per_sample * freq * qformat.channels();
+
 	const QSettings settings(Qmmp::configFile(), QSettings::IniFormat);
 	const QString saved_device_name = settings.value("QTMULTIMEDIA/device").toString();
 
@@ -111,6 +121,11 @@ qint64 OutputQtMultimedia::latency()
 
 qint64 OutputQtMultimedia::writeAudio(unsigned char *data, qint64 maxSize)
 {
+	if (!m_output->bytesFree()) {
+		//If the buffer is full, waiting for some bytes to be played:
+		//trying to play maxSize bytes, but not more than half of buffer.
+		usleep(qMin(maxSize, static_cast<qint64>(m_output->bufferSize() / 2)) * 1000000 / m_bytes_per_second);
+	}
 	return m_buffer->write((const char*)data, maxSize);
 }
 
diff --git a/src/plugins/Output/qtmultimedia/outputqtmultimedia.h b/src/plugins/Output/qtmultimedia/outputqtmultimedia.h
index ab60ce290..ea69b9b3f 100644
--- a/src/plugins/Output/qtmultimedia/outputqtmultimedia.h
+++ b/src/plugins/Output/qtmultimedia/outputqtmultimedia.h
@@ -47,6 +47,7 @@ public:
 private:
     QScopedPointer<QAudioOutput> m_output;
     QIODevice *m_buffer;
+    qint64 m_bytes_per_second;
 };