在规定的时间Qt中获取视频帧 [英] Getting video frame in provided time Qt

问题描述

我想做的是在某个时间(例如20秒)获取视频帧. 我知道我可以做这样的事情-倒带视频并暂停它:

What I want to do is to get video frame at some time (for example at 20 sec). I know I could do something like this - rewind video and pause it:

QMediaPlayer* player = new QMediaPlayer;
...
player->play();
player->setPosition(20000);
player->pause();

但是有没有更优雅的解决方案(对我来说这似乎是个hack，因为我不需要整个视频，但有时只需要一帧)?

But is there some more elegant solution (this seems like a hack to me since I don't need whole video but only a frame at some time)?

推荐答案

以下步骤可以帮助您从视频文件中捕获帧.

项目级别

1. QT + =多媒体

代码级别

1. 启动QMediaplayer对象(QMediaPlayer(QObject父级，QMediaPlayer :: VideoSurface)
2. 将QMediaplayer.setVideoOutput设置为(QAbstractVideoSurface的子类)
3. QAbstractVideoSurface的子类应重新实现受支持的方法:PixelFormats，isFormatSupported，开始，存在
   4.通过 present 方法，我们可以获取每一帧的图像缓冲区
4. 使用QMediaplayer加载视频文件
5. setMute = true(音频)
6. 将所需位置(以毫秒为单位)设置为QMediaplayer对象
7. 开始播放方法
8. 从 present 方法将接收到的数据缓冲区转换为QImage，然后转换为QPixmap(如果需要).
9. 一旦获得了像素图，就可以使用它加载到小部件中(例如:在QLabel中)
10. 立即暂停视频文件的播放(如果您需要捕获其他帧.其他明智的选择stop()而不是pause()).可以使用从子类的对象(QAbstractVideoSurface)到QMediaPlayer对象的信号槽
11. 完成后，调用QAbstractVideoSurface子类的stop方法，然后调用QMediaplayer

1. Initiate QMediaplayer object (QMediaPlayer(QObject parent, QMediaPlayer::VideoSurface)
2. set QMediaplayer.setVideoOutput to(Subclass of QAbstractVideoSurface)
3. Subclass of QAbstractVideoSurface should re-implement the methods supportedPixelFormats, isFormatSupported, start, present
   4.From the present method we can get the image buffer of each frame
4. Load the video file using QMediaplayer
5. setMute = true(audio)
6. Set the needed position in milliseconds to the QMediaplayer object
7. Start play method
8. From the present method convert the received data buffer to QImage and then to QPixmap(if needed).
9. Once got the pixmap, use it to load in a widget (example: In a QLabel)
10. Immediately pause the video file from playing (if you need to capture some other frame. Other wise stop() instead of pause()). This can be done using signal-slot from subclass's object (QAbstractVideoSurface) to QMediaPlayer object
11. When done,call the stop method of sub class of QAbstractVideoSurface and then the QMediaplayer

上述示例应用程序可以在此处

Above said example application can be found here

(应用程序屏幕截图)

打开视频文件:浏览并选择一个视频文件
滑块:选择所需的位置
捕获:捕获图像并在QLabel中查看
保存:保存捕获的图像

Open Video File : Browse and select a video file
Slider : select the position you want
Capture : capture the image and view in a QLabel
Save : Save the captured image

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