如何在Qt Creator中的Qt Widgets应用程序中播放本地视频？

Question

This is probably a very noob question... I am very new to Qt, and trying programming in Qt creator. Now I created a new Qt Widgets Application from Qt creator, and want to play a video with it. I now have the following 6 files in my project:

• Project
  • Project.pro
  • Headers
    • videoplayer.h
  • Sources
    • main.cpp
    • videoplayer.cpp
  • Forms
    • videoplayer.ui
  • Other files
    • /Users/somebody/somewhere
      • Demo.mp4

Where and how exactly should I write my code to make it play Demo.mp4 when I run my application (maybe using some tools called QVideoPlayer)? Should I add some Qwidget onto my videoplayer.ui? I now have four buttons "play", "pause", "full_screen" and "rearrange" on my videoplayer.ui. The result I want is something with features of:

• Press play button to play Demo.mp4 on the top-left of the entire window
• Press Pause to pause
• Press full_screen to enter full screen (if QMediaPlayer can enter/quit full screen itself, then this feature is not necessary)
• press rearrange to put the playing window from top-left to top-right
• additional: fast forward and rewind (again, if QVideoPlayer or something Qt provided not already has this feature)

Answer 1

You are looking for Qt Multimedia Widgets . (You might need to install extra packages when running Linux).

The basic idea goes like this:

• On the UI side of things you use a QVideoWidget . This is where the video is displayed.
  • This is what you would add to your .ui file.
  • Note the fullScreen property.
• On the logic side of things you use a QMediaPlayer which controls what is played and when it's played.
  • The two are connected by calling QMediaPlayer::setVideoOutput(yourVideoWidgetGoesHere); .
  • Then you add a QMediaPlaylist to your QMediaPlayer .
  • Finally call QMediaPlayer::play() and you should be good to go

Then you want some basic controls if this works so far. QMediaPlayer provides the following slots that exactly do as their names suggest:

• pause()
• play()
• stop()
• setPosition(int) , argument is in milliseconds. duration() might be of interest.
• setVolume(int) and setMuted(bool) . Volume goes from 0 to 100.
• setPlaybackRate(double)
• Metadata is available via metaData(QString key) : http://qt-project.org/doc/qt-5/qmediaobject.html#metaData

Each of these also has a corresponding change signal, very interesting for you is probably the positionChanged(int) signal to update a slider or something similar with the current position.

Basic example courtesy of the Qt documentation:

player = new QMediaPlayer;

playlist = new QMediaPlaylist(player);
playlist->addMedia(QUrl("http://example.com/myclip1.mp4"));
playlist->addMedia(QUrl("http://example.com/myclip2.mp4"));

videoWidget = new QVideoWidget;
player->setVideoOutput(videoWidget);

videoWidget->show();
playlist->setCurrentIndex(1);
player->play(); 

Answer 2

What you are looking for is to implement a QMediaPlayer if you are on Qt 5 , a QVideoPlayer if you are on Qt 4.4

For QMediaPlayer , you'll have to use a following implementation for adding one movie :

QMediaPlayer *player = new QMediaPlayer;
player->setMedia(QUrl::fromLocalFile("/users/somebody/somewhere/demo.mp4"));
player->setVolume(10);
player->play();