Question

嘿，堆栈目前正在尝试创建一些只从本地源播放视频文件的基本代码（试图让它工作然后尝试并实现rtsp）。下面是我目前的代码。如果有人能给我一个想法，我会出错，这将是伟大的。

目前代码失败并显示错误

C：\ Qt \ Qt5.1.0 \ 5.1.0 \ msvc2010_opengl \ examples \ multimediawidgets \ videographicsitem \ main.cpp：58：错误：C2664：'QGraphicsScene :: addItem'：无法从'QGraphicsVideoItem *'转换参数1到'QGraphicsItem *' 指向的类型是无关的;转换需要reinterpret_cast，C风格的转换或函数式转换

我认为我必须对插入到additem的变量进行类型转换。但是不知道如何用两个Qclasses做到这一点。如果有人有一个基本播放器的例子，它只包含一个视频帧并播放第二个你启动该程序（最好不是播放按钮）。如果有人有类似的东西，请让我知道，因为这将使我的生活更轻松。 Main.cpp的

#include "videoplayer.h"

#include <QApplication>
#include <QGraphicsView>

int main(int argc, char **argv)
{
QApplication app(argc, argv);
//VideoPlayer player;
//QGraphicsView graphicsView;
QMediaPlayer *player ;

QGraphicsVideoItem *item;
QGraphicsView *graphicsView;
QGraphicsScene *scene;
player->setVideoOutput(item);
// scene->addItem(item);
graphicsView->scene()->addItem(item);
graphicsView->show();

player->setMedia(QUrl("rtsp://192.168.100.58:8554/stream"));
player->play();

graphicsView->show();

return app.exec();
}

Videoplayer.cpp

#include "videoplayer.h"

#include <QtWidgets>
#include <QVideoSurfaceFormat>
#include <QGraphicsVideoItem>

VideoPlayer::VideoPlayer(QWidget *parent)
: QWidget(parent)
, mediaPlayer(0, QMediaPlayer::VideoSurface)
, videoItem(0)
, playButton(0)
, positionSlider(0)
{
videoItem = new QGraphicsVideoItem;
videoItem->setSize(QSizeF(640, 480));

QGraphicsScene *scene = new QGraphicsScene(this);
QGraphicsView *graphicsView = new QGraphicsView(scene);

scene->addItem(videoItem);

QSlider *rotateSlider = new QSlider(Qt::Horizontal);
rotateSlider->setRange(-180,  180);
rotateSlider->setValue(0);

connect(rotateSlider, SIGNAL(valueChanged(int)),
        this, SLOT(rotateVideo(int)));

QAbstractButton *openButton = new QPushButton(tr("Open..."));
connect(openButton, SIGNAL(clicked()), this, SLOT(openFile()));

playButton = new QPushButton;
playButton->setEnabled(false);
playButton->setIcon(style()->standardIcon(QStyle::SP_MediaPlay));

connect(playButton, SIGNAL(clicked()),
        this, SLOT(play()));

positionSlider = new QSlider(Qt::Horizontal);
positionSlider->setRange(0, 0);

connect(positionSlider, SIGNAL(sliderMoved(int)),
        this, SLOT(setPosition(int)));

QBoxLayout *controlLayout = new QHBoxLayout;
controlLayout->setMargin(0);
controlLayout->addWidget(openButton);
controlLayout->addWidget(playButton);
controlLayout->addWidget(positionSlider);

QBoxLayout *layout = new QVBoxLayout;
layout->addWidget(graphicsView);
layout->addWidget(rotateSlider);
layout->addLayout(controlLayout);

setLayout(layout);

mediaPlayer.setVideoOutput(videoItem);
connect(&mediaPlayer, SIGNAL(stateChanged(QMediaPlayer::State)),
        this, SLOT(mediaStateChanged(QMediaPlayer::State)));
connect(&mediaPlayer, SIGNAL(positionChanged(qint64)), this, SLOT(positionChanged(qint64)));
connect(&mediaPlayer, SIGNAL(durationChanged(qint64)), this, SLOT(durationChanged(qint64)));
}

VideoPlayer::~VideoPlayer()
{
}


void VideoPlayer::openFile()
{
QString fileName = QFileDialog::getOpenFileName(this, tr("Open Movie"),QDir::homePath());
//QString fileName = "rtsp://192.168.100.58:8554/stream";
if (!fileName.isEmpty()) {
    mediaPlayer.setMedia(QUrl::fromLocalFile(fileName));

    playButton->setEnabled(true);
}
}

void VideoPlayer::play()
{
switch(mediaPlayer.state()) {
case QMediaPlayer::PlayingState:
    mediaPlayer.pause();
    break;
default:
    mediaPlayer.play();
    break;
}
}

Videoplayer.h

#ifndef VIDEOPLAYER_H
#define VIDEOPLAYER_H

#include <QMediaPlayer>
#include <QMovie>
#include <QWidget>

class QAbstractButton;
class QSlider;
class QGraphicsVideoItem;

class VideoPlayer : public QWidget
{
Q_OBJECT

public:
VideoPlayer(QWidget *parent = 0);
~VideoPlayer();

QSize sizeHint() const { return QSize(800, 600); }

public slots:
void openFile();
void play();

private slots:
void mediaStateChanged(QMediaPlayer::State state);
void positionChanged(qint64 position);
void durationChanged(qint64 duration);
void setPosition(int position);
void rotateVideo(int angle);

private:
QMediaPlayer mediaPlayer;
QGraphicsVideoItem *videoItem;
QAbstractButton *playButton;
QSlider *positionSlider;
};

#endif

的.pro

TEMPLATE = app
TARGET = videographicsitem

QT += multimedia multimediawidgets

HEADERS   += videoplayer.h

SOURCES   += main.cpp \
         videoplayer.cpp

target.path = $$[QT_INSTALL_EXAMPLES]/multimediawidgets/videographicsitem
INSTALLS += target

QT+=widgets

还试过这个

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QMediaPlayer media;
const QString file = "C:/Users/nick.herniman/Downloads/big_buck_bunny_1080p_h264.mov";
QUrl url(QFileInfo(file).absoluteFilePath());
media.setMedia(url);
media.play();
return a.exec();
}

哪个有效，但只播放文件的音频，任何人都知道我在这里做错了什么（它是否需要在gui窗口中，或者我可以在控制台应用程序中执行此操作）？

Answer 1

没有什么奇怪的。： - ）

当编译器知道QGraphicsVideoItem是QGraphicsItem时，它会有所帮助。并且为了使编译器知道这一点，#include <QGraphicsVideoItem>应该存在。

我知道，你在Videoplayer.cpp中拥有它。但是main.cpp只看到声明了一个类QGraphicsVideoItem。你做了很好的前瞻宣言。但这个类是什么......没有办法知道main.cpp中的编译器。将#include <QGraphicsVideoItem>添加到您的main.cpp。

Answer 2

在Qt5中尝试这个最简单的例子：

QMediaPlayer *mediaPlayer = new QMediaPlayer(this, QMediaPlayer::VideoSurface);
QGraphicsVideoItem *videoItem = new QGraphicsVideoItem;
videoItem->setPos(100,100);
QGraphicsScene *scene = new QGraphicsScene(this);
ui->GV_VideoPlayer->setScene(scene);
scene->addItem(videoItem);
QString fileName = "/root/sampleVideos/videoplayback.mp4";
if(!fileName.isEmpty())
{
    mediaPlayer->setMedia(QUrl::fromLocalFile(fileName));
}
mediaPlayer->play();
mediaPlayer->setVideoOutput(videoItem);

Answer 3

QT文档陈述一个非常相似的例子（http://qt-project.org/doc/qt-5.0/qtmultimedia/qgraphicsvideoitem.html）实际上很奇怪，而对象实际上并不相关。除此之外，仅查看QT文档，因为我暂时没有使用QT - 创建虚拟QGraphicsItem，将其设置为QGraphicsVideoItem的父项，然后添加该虚拟项到现场帮忙？我猜它会像这样

QGraphicsItem* dummy = new QGraphicsItem;
item = new QGraphicsVideoItem(dummy);
graphicsView->scene()->addItem(dummy);

Qt5视频播放器QtMultimedia QGraphicsVideoItem

3 个答案: