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Prevent image buffer exhaustion on Android using Qt #938

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Merged
merged 3 commits into from
Apr 28, 2025
Merged

Prevent image buffer exhaustion on Android using Qt #938

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157d92e
Prevent image buffer exhaustion on Android using Qt
m7913d Apr 21, 2025
efb08a0
Support multiple threads to process video frames in Qt
m7913d Apr 26, 2025
02a7b69
Do not start processing new frames during shutdown.
m7913d Apr 27, 2025
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38 changes: 35 additions & 3 deletions example/ZXingQtReader.h
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
#include <QAbstractVideoFilter>
#else
#include <QThreadPool>
#include <QVideoFrame>
#include <QVideoSink>
#endif
Expand Down Expand Up @@ -333,7 +334,16 @@ class BarcodeReader : public QObject, private ReaderOptions
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
BarcodeReader(QObject* parent = nullptr) : QAbstractVideoFilter(parent) {}
#else
BarcodeReader(QObject* parent = nullptr) : QObject(parent) {}
BarcodeReader(QObject* parent = nullptr) : QObject(parent)
{
_pool.setMaxThreadCount(1);
}
~BarcodeReader()
{
_pool.setMaxThreadCount(0);
_pool.waitForDone(-1);
}

#endif

// TODO: find out how to properly expose QFlags to QML
Expand Down Expand Up @@ -373,10 +383,11 @@ class BarcodeReader : public QObject, private ReaderOptions
ZQ_PROPERTY(bool, isPure, setIsPure)

// For debugging/development
int runTime = 0;
QAtomicInt runTime = 0;
Q_PROPERTY(int runTime MEMBER runTime)

public slots:
// Function should be thread safe, as it may be called from a separate thread.
ZXingQt::Barcode process(const QVideoFrame& image)
{
QElapsedTimer t;
Expand All @@ -403,6 +414,7 @@ public slots:
#else
private:
QVideoSink *_sink = nullptr;
QThreadPool _pool;

public:
void setVideoSink(QVideoSink* sink) {
Expand All @@ -413,9 +425,29 @@ public slots:
disconnect(_sink, nullptr, this, nullptr);

_sink = sink;
connect(_sink, &QVideoSink::videoFrameChanged, this, &BarcodeReader::process);
connect(_sink, &QVideoSink::videoFrameChanged, this, &BarcodeReader::onVideoFrameChanged, Qt::DirectConnection);
}
void onVideoFrameChanged(const QVideoFrame& frame)
{
if (_pool.activeThreadCount() >= _pool.maxThreadCount())
return; // we are busy => skip the frame

_pool.start([this, frame](){process(frame);});
}
Q_PROPERTY(QVideoSink* videoSink MEMBER _sink WRITE setVideoSink)
Q_PROPERTY(int maxThreadCount READ maxThreadCount WRITE setMaxThreadCount)
int maxThreadCount () const
{
return _pool.maxThreadCount();
}
void setMaxThreadCount (int maxThreadCount)
{
if (_pool.maxThreadCount() != maxThreadCount) {
_pool.setMaxThreadCount(maxThreadCount);
emit maxThreadCountChanged();
}
}
Q_SIGNAL void maxThreadCountChanged();
#endif

};
Expand Down
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