c++ - 内存泄漏(OpenCV + QML)

Question

我正在尝试在 QML 图像中显示 OpenCV Mat。

我使用 OpenCV 从相机抓取帧，帧在 QML 中成功显示，但内存使用量随着时间的推移而增加。我该如何解决？这是我的代码:

主要.cpp

#include <QGuiApplication>
#include "videoprovider.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    VideoProvider videoProvider;
    return app.exec();
}

VideoProvider.h

#ifndef VIDEOPROVIDER_H
#define VIDEOPROVIDER_H

#include <QObject>
#include <QFuture>
#include <QImage>
#include <QQmlApplicationEngine>
#include <QQuickImageProvider>
#include <opencv2/opencv.hpp>

class VideoProvider : public QObject, public QQuickImageProvider
{
    Q_OBJECT
public:
    explicit VideoProvider();
    QPixmap requestPixmap(const QString &id, QSize *size, const QSize& requestedSize);

signals:
    void frameChanged();

public slots:
    void framePainted();

private:
    QQmlApplicationEngine engine;
    bool readyfor;
    cv::Mat mat;
    QImage outputImage;
    void process();
};

#endif // VIDEOPROVIDER_H

VideoProvider.cpp

#include <QQmlContext>
#include <QtConcurrent/QtConcurrent>
#include <QDebug>
#include <QThread>
#include "videoprovider.h"
#include <QQuickImageProvider>

VideoProvider::VideoProvider() : QQuickImageProvider (QQuickImageProvider :: Pixmap)
{
    engine.rootContext()->setContextProperty("videoProvider", this);
    engine.addImageProvider(QLatin1String ("videoCapture"), this);
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    readyfor = true;
    QtConcurrent::run(this, VideoProvider::process);
}

void VideoProvider::framePainted()
{
    readyfor = true;
}

void VideoProvider::process()
{
    cv::VideoCapture capture(0);

    while(true){

        QThread::currentThread()->msleep(80);

        if(!readyfor) continue;

        mat.release();
        capture >> mat;

        if(mat.empty())
        {
            qDebug()<<"disconnect";
        }
        else
        {
            readyfor = false;
            cv::cvtColor(mat, mat, cv::COLOR_BGR2RGB);
            outputImage = QImage((uchar*)mat.data, mat.cols, mat.rows, mat.step, QImage::Format_RGB888);
            emit frameChanged();
        }
    }

    capture.release();
}

QPixmap VideoProvider::requestPixmap(const QString &id, QSize *size, const QSize& requestedSize)
{
    return QPixmap::fromImage(outputImage);
}

主.qml

import QtQuick 2.6
import QtQuick.Window 2.2

Window
{
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
    id: root

    Image{
        id: videoLayer
        anchors.fill: parent
        cache: false

        onSourceChanged:{
            videoProvider.framePainted();
        }
    }

    Connections
    {
        target: videoProvider
        property int frameCounter: 0

        onFrameChanged:
        {
            videoLayer.source = "image://videoCapture/hoge" + frameCounter;
            frameCounter ^= 1;
        }
    }
}

我发现它发生在我向 QML 发送信号 (emit frameChanged();) 时。

更新:

Valgrind 日志:

==18038== Memcheck, a memory error detector
==18038== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==18038== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==18038== Command: ./prog
==18038== 
QML debugging is enabled. Only use this in a safe environment.
==18038== Warning: noted but unhandled ioctl 0x30000001 with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Warning: noted but unhandled ioctl 0x27 with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Warning: noted but unhandled ioctl 0x7ff with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Warning: noted but unhandled ioctl 0x25 with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Warning: noted but unhandled ioctl 0x17 with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Warning: set address range perms: large range [0x200000000, 0x500000000) (noaccess)
==18038== Warning: set address range perms: large range [0x500000000, 0x700000000) (noaccess)
==18038== Warning: noted but unhandled ioctl 0x19 with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Warning: noted but unhandled ioctl 0x21 with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Warning: noted but unhandled ioctl 0x1b with no size/direction hints.
==18038==    This could cause spurious value errors to appear.
==18038==    See README_MISSING_SYSCALL_OR_IOCTL for guidance on writing a proper wrapper.
==18038== Thread 8 Thread (pooled):
==18038== Invalid read of size 4
==18038==    at 0xAF682D0: QImage::~QImage() (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Gui.so.5.9.1)
==18038==    by 0x40570F: VideoProvider::process() (videoprovider.cpp:50)
==18038==    by 0x406AEB: QtConcurrent::VoidStoredMemberFunctionPointerCall0<void, VideoProvider>::runFunctor() (qtconcurrentstoredfunctioncall.h:205)
==18038==    by 0x405FC6: QtConcurrent::RunFunctionTask<void>::run() (qtconcurrentrunbase.h:136)
==18038==    by 0xBC44BA2: ??? (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Core.so.5.9.1)
==18038==    by 0xBC48849: ??? (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Core.so.5.9.1)
==18038==    by 0xCE456B9: start_thread (pthread_create.c:333)
==18038==    by 0xC9773DC: clone (clone.S:109)
==18038==  Address 0x23d1b260 is 0 bytes inside a block of size 128 free'd
==18038==    at 0x4C2F24B: operator delete(void*) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18038==    by 0xAF682F3: QImage::~QImage() (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Gui.so.5.9.1)
==18038==    by 0x4047CB: VideoProvider::~VideoProvider() (videoprovider.h:11)
==18038==    by 0x403A34: main (main.cpp:8)
==18038==  Block was alloc'd at
==18038==    at 0x4C2E0EF: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18038==    by 0xAF656BE: QImageData::create(unsigned char*, int, int, int, QImage::Format, bool, void (*)(void*), void*) (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Gui.so.5.9.1)
==18038==    by 0xAF65971: QImage::QImage(unsigned char*, int, int, int, QImage::Format, void (*)(void*), void*) (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Gui.so.5.9.1)
==18038==    by 0x4056E2: VideoProvider::process() (videoprovider.cpp:50)
==18038==    by 0x406AEB: QtConcurrent::VoidStoredMemberFunctionPointerCall0<void, VideoProvider>::runFunctor() (qtconcurrentstoredfunctioncall.h:205)
==18038==    by 0x405FC6: QtConcurrent::RunFunctionTask<void>::run() (qtconcurrentrunbase.h:136)
==18038==    by 0xBC44BA2: ??? (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Core.so.5.9.1)
==18038==    by 0xBC48849: ??? (in /home/dmytro/Qt/5.9.1/gcc_64/lib/libQt5Core.so.5.9.1)
==18038==    by 0xCE456B9: start_thread (pthread_create.c:333)
==18038==    by 0xC9773DC: clone (clone.S:109)

Answer 1

I grab frames from camera with OpenCV, the frames are displayed successfully in QML, but memory usage increases with time. How can I fix it?

下面的前提条件是视频捕获处理图像的速度不超过每帧 1000 毫秒/80 毫秒 = 每秒 12.5 帧(实际上由于处理时间而更少)，而标准相机速率在 25 到 80 的范围内。那这就是为什么图像帧卡在 OpenCV 等的内部缓冲区中的原因。只要操作系统仍然能够放弃其他线程的时间片，在这里等待 1 到 5 毫秒(必须足够)不会有什么坏处。我个人使用 C++ 11 中的条件变量或来自 Qt而不是“ sleep ”。使用条件变量，我们可以更优雅地中断等待等。

while(true){

    QThread::currentThread()->msleep(80); // too much wait
    // also just do QThread::msleep instead

    if(!readyfor) continue;

    mat.release();
    capture >> mat