How to create a .mp4 Video from a collection of QOpenGLFramebufferObjects /QImages / Glunit textures

Roby Brundle

I am developing a Qt app for iOS, Android & OSX.

Situation:
I have an std::vector of QOpenGLFramebufferObjects. Each QOpenGLFramebufferObject can of course provide its own QImage or a GLunit texture by doing a takeTexture. So you can also say that I have a collection of QImages or GLunit textures.

Problem:
I want to create a .mp4 video file out of these QImages/QOpenGLFramebufferObjects which works on iOS, Android & OSX.

How should I do this? Any examples doing this with Qt? Which classes in Qt should I be looking into?

I am thinking to use ffmpeg or GStreamer whatever works best in Qt. But I want to know how to pass these QImages or Glunit textures to create the video. Is there Qt support to do this without having to use a 3d party library?

Should I use QVideoEncoderSettings to create the video?
Are there any examples in Qt doing this?
Which classes/components in Qt I should be looking into?

Is there something in Qt Multimedia that I can use?
If not then what is the best option wrt to making this work on Android & iOS?

PS :
I am using Qt 5.9.1 commercial version on Android & iOS

SGaist

Hi,

Something is not clear from your description, do you want your application to record a video file on all three platforms ? Or do you want to generate video files that can be played on all these platforms ?

If the former, what is the source of images ? Are you using widgets or QtQuick ?

Roby Brundle

@SGaist I want to generate video files that can be played on all 3 platforms.

The source QImages are are some are QOpenGLFramebufferObjects which are populated after some processing using OpenGL.

I am using Qt Quick commercial version for Android & iOS. And working on Qt 5.9.1.

Simplistically saying, I just want to create a video file from QImages or Glunit textures whichever option works with Qt.

SGaist

Well, I'm sorry to say that it's still not that clear, so let me rephrase that: will your application create these video files on iOS and Android ? Or are you creating a desktop only application that should create these video files ?

In any case, QOpenGLFramebufferObject has a toImage method that returns a QImage.

Roby Brundle

@SGaist Yes. My application will create these video files on iOS and Android. It is not a desktop only application. It is primarily for iOS & Android. But the application runs on MacOS as well which is my development environment.

Yes. QOpenGLFramebufferObject has toImage method to return a QImage. I already know that. But my question starts after this.

Rephrasing my question here again:
Consider you have 15 QOpenGLFramebufferObjects in memory. Each one of course can return a QImage. I wan to create a video (.mp4) out of these 15 QImages. How do I do this with Qt.

And of course, as I said I am running commercial paid version of Qt based Qt latest 5.9.1 released recently. It is a Qt quick based application.

SGaist

QMediaRecorder would be the starting point.

Note that there's no system encoder for h264, it's a non free-format.

Roby Brundle

@SGaist How can I pass QImages into QMediaRecorder & create a video out of it?
Is there a example or some code snippet you could point to?

Note that I don't need audio. I just want to programmatically create a video out of multiple QImages. And, this is has nothing to do with the camera . I am not trying to get images from camera.

Trying to see the examples of QMediaRecorder, all of them hooking on to the camera which I don't need to do with my program . Simply, I have some QImages in memory. Want to create a video from say 10 QImages.

SGaist

You need to create a QMediaObject that will provide the images to QMediaRecorder.

Roby Brundle

@SGaist said in How to create a .mp4 Video from a collection of QOpenGLFramebufferObjects /QImages / Glunit textures:

QMediaObject

Is there an example doing something similar? would be really helpful if you could point to an example doing something close

SGaist

AFAIK, no. You will have to take some inspiration from the Qt Multimedia sources.