export h.264 from QGraphicsScene?

davecotter

can i use QMediaRecorder and QMediaCaptureSession to write an h.264 file from a QGraphicsScene? or from a QVideoSink? or from a QGraphicsItem?

like, i want to export an MP4 video (including audio) that i can currently play via a QGraphicsScene, and the scene does have a few layers: some graphics and text overlays.

seems i can record live from a camera / window / screen, but can i record directly from a QGraphicsScene?

or, how would i accomplish what i'm attempting, without using 3rd party libs?

SGaist

Hi,

Since you are talking about QVideoSink, you are using Qt 6.

So QVideoSink would be an option AFAIK. Note that h264 might not be available for encoding without additional codec packages. In any case, if you want to recompress a video, you should rather use ffmpeg directly.

davecotter

my only platforms are macOS and Windows, and i believe both media back ends support export to h.264. so, say i am going to try to do this without ffmpeg, how would i connect the video sink to the built-in QMediaCaptureSession ?

SGaist

I think it should be doable with QMediaRecorder::serVideoSink.

davecotter

doesn't setVideoSink() tell the QMediaRecorder to send a copy of the video to a viewer? it's not setting the INPUT of the recorder, it's setting an output.

How can i connect an audio stream input, and a QGraphicsScene video input, so the recorder creates a new mp4 file?

SGaist

You are correct, I misread the method documentation.

Currently, from the looks of it, you cannot do it directly.

Some sort of virtual camera would be needed as I don't see any generic "media object" class that can be used as input for QMediaRecorder.