framegrabber.cpp

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// Copyright (C) 2026 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
 
#include "framegrabber_p.h"
 
#include "mediabackendutils_p.h"
 
#include <QtTest/qtest.h>
#include <QtTest/private/qtestblacklist_p.h>
#include <QtMultimedia/qvideoframe.h>
#include <QtCore/q20vector.h>
#include <QtCore/qcoreapplication.h>
#include <QtCore/qelapsedtimer.h>
#include <QtCore/qscopeguard.h>
 
#include <utility>
 
QT_BEGIN_NAMESPACE
 
namespace QtMultimediaTest {
 
std::chrono::milliseconds surfaceCaptureTestTimeout()
{
    // A blacklisted test is expected to fail, so don't make it wait for the full
    // timeout to do so.
    if (const char *testFunction = QTest::currentTestFunction();
        testFunction && QTestPrivate::checkBlackLists(testFunction, QTest::currentDataTag())) {
        return std::chrono::seconds(1);
    }
 
    if (isCI())
        return std::chrono::seconds(60);
    return std::chrono::seconds(5);
}
 
[[nodiscard]] static std::optional<std::chrono::milliseconds> maxFrameInterval(std::optional<qreal> frameRate)
{
    if (!frameRate || *frameRate <= 0)
        return std::nullopt;
 
    // Slightly longer than the nominal interval. More forgiving on loaded CI machines.
    const qreal margin = isCI() ? 3.0 : 1.5;
    return std::chrono::milliseconds(qRound64(1000.0 / *frameRate * margin));
}
 
static qint64 startTimeOf(const QVideoFrame &frame)
{
    return frame.startTime();
}
 
static qint64 startTimeOf(const VideoFrameInfo &info)
{
    return info.startTime;
}
 
static VideoFrameInfo makeVideoFrameInfo(const QVideoFrame &frame)
{
    return VideoFrameInfo{
        frame.isValid(),
        frame.size(),
        frame.pixelFormat(),
        frame.startTime(),
        frame.endTime(),
    };
}
 
FrameGrabber::FrameGrabber()
{
    connect(this, &QVideoSink::videoFrameChanged, this, &FrameGrabber::onFrameReceived);
}
 
void FrameGrabber::onFrameReceived(const QVideoFrame &frame)
{
    m_frameInfos.push_back(makeVideoFrameInfo(frame));
    if (m_retainVideoFrames)
        m_videoFrames.push_back(frame);
 
    if (!frame.isValid()) {
        // A null-frame ends the stream, and the next valid frame starts a new one.
        resetFirstFrame();
        m_streamStarted = false;
    } else if (!m_streamStarted) {
        m_firstFrameInfo = m_frameInfos.back();
        if (m_retainFirstVideoFrame)
            m_firstVideoFrame = frame;
        m_streamStarted = true;
    }
}
 
const std::vector<VideoFrameInfo> &FrameGrabber::getFrameInfos() const
{
    return m_frameInfos;
}
 
std::vector<VideoFrameInfo> FrameGrabber::waitAndTakeFrameInfos(
    size_t minCount,
    std::optional<qreal> expectedFrameRate,
    qint64 noOlderThanTime)
{
    return waitAndTake(m_frameInfos, minCount, expectedFrameRate, noOlderThanTime);
}
 
std::vector<QVideoFrame> FrameGrabber::waitAndTakeVideoFrames(
    size_t minCount,
    std::optional<qreal> expectedFrameRate,
    qint64 noOlderThanTime)
{
    // Holding on to QVideoFrames can stall backends that use a fixed-size
    // frame pool, so only retain them while the caller is waiting for them.
    m_retainVideoFrames = true;
    const auto stopRetaining = qScopeGuard([this] {
        m_retainVideoFrames = false;
        m_videoFrames.clear();
    });
 
    return waitAndTake(m_videoFrames, minCount, expectedFrameRate, noOlderThanTime);
}
 
template <typename Frame>
std::vector<Frame> FrameGrabber::waitAndTake(
    std::vector<Frame> &frames,
    size_t minCount,
    std::optional<qreal> expectedFrameRate,
    qint64 noOlderThanTime)
{
    m_frameInfos.clear();
    m_videoFrames.clear();
 
    const auto enoughFramesOrStopped = [this, &frames, minCount, noOlderThanTime]() -> bool {
        if (m_stopped)
            return true; // Stop waiting
 
        // ensure that all signals &QVideoSink::videoFrameChanged have been processed
        QCoreApplication::processEvents(QEventLoop::AllEvents);
 
        if (noOlderThanTime > 0) {
            // Reject frames older than noOlderThanTime
            q20::erase_if(frames, [noOlderThanTime](const Frame &frame) {
                return startTimeOf(frame) <= noOlderThanTime;
            });
        }
 
        return frames.size() >= minCount;
    };
 
    // The first frame may be delayed by initialization. Beyond that, each
    // frame is due within the frame interval.
    std::chrono::milliseconds timeout = surfaceCaptureTestTimeout();
    std::optional<std::chrono::milliseconds> interval = maxFrameInterval(expectedFrameRate);
    if (interval)
        timeout += *interval * qint64(minCount);
 
    if (!QTest::qWaitFor(enoughFramesOrStopped, timeout))
        return {};
 
    if (m_stopped)
        return {};
 
    return std::exchange(frames, {});
}
 
bool FrameGrabber::waitForFirstFrame()
{
    const auto firstFrameReceivedOrStopped = [this] {
        return m_stopped || m_firstFrameInfo;
    };
 
    if (!QTest::qWaitFor(firstFrameReceivedOrStopped, surfaceCaptureTestTimeout()))
        return false;
 
    return !m_stopped;
}
 
std::optional<VideoFrameInfo> FrameGrabber::tryWaitForFirstFrameInfo()
{
    if (!waitForFirstFrame())
        return std::nullopt;
 
    return m_firstFrameInfo;
}
 
std::optional<QVideoFrame> FrameGrabber::consumeFirstVideoFrame()
{
    Q_ASSERT_X(
        m_retainFirstVideoFrame,
        "FrameGrabber::consumeFirstVideoFrame",
        "setRetainFirstVideoFrame() must be enabled before the stream starts");
 
    if (!waitForFirstFrame())
        return std::nullopt;
 
    return std::exchange(m_firstVideoFrame, std::nullopt);
}
 
void FrameGrabber::setRetainFirstVideoFrame(bool retain)
{
    m_retainFirstVideoFrame = retain;
    if (!retain)
        m_firstVideoFrame.reset();
}
 
void FrameGrabber::resetFirstFrame()
{
    m_firstFrameInfo.reset();
    m_firstVideoFrame.reset();
}
 
std::optional<std::chrono::milliseconds> FrameGrabber::durationBetweenFrames(
    qsizetype frameCount,
    std::optional<qreal> expectedFrameRate)
{
    Q_ASSERT(frameCount > 0);
 
    using namespace std::chrono;
 
    QElapsedTimer timer;
    QElapsedTimer sinceLastFrame;
    qsizetype framesReceived = 0;
 
    QObject context;
    connect(this, &QVideoSink::videoFrameChanged, &context, [&]() {
        if (framesReceived++ == 0)
            timer.start();
        sinceLastFrame.start();
    });
 
    std::optional<milliseconds> maxInterval = maxFrameInterval(expectedFrameRate);
 
    // Fails early if the frames stop coming at the expected rate.
    auto allFramesReceivedOrStalled = [&]() {
        if (framesReceived > frameCount)
            return true;
        return maxInterval && framesReceived > 0 && sinceLastFrame.hasExpired(maxInterval->count());
    };
 
    // Without an expected frame rate, assume the stream runs at 1 FPS minimum.
    // With one, the first frame gets the global timeout, and each of the rest are
    // checked against the frame interval above.
    milliseconds timeout = surfaceCaptureTestTimeout();
    if (maxInterval)
        timeout += *maxInterval * frameCount;
    else
        timeout = isCI() ? 10s * frameCount : 2s * frameCount;
 
    if (!QTest::qWaitFor(allFramesReceivedOrStalled, timeout) || framesReceived <= frameCount)
        return std::nullopt;
 
    return milliseconds(timer.elapsed() / frameCount);
}
 
bool FrameGrabber::isStopped() const
{
    return m_stopped;
}
 
void FrameGrabber::onCaptureActiveChanged(bool active)
{
    // Not all backends end the stream with a null-frame, so treat activation
    // as the start of a new stream as well.
    if (active) {
        resetFirstFrame();
        m_streamStarted = false;
    }
}
 
void FrameGrabber::stop()
{
    qWarning() << "Stopping grabber";
    m_stopped = true;
}
 
} // namespace QtMultimediaTest
 
QT_END_NAMESPACE
 
#include "moc_framegrabber_p.cpp"