Den 18-04-2016 kl. 05:46 skrev Andy:
Goal: generate video with a user-specified resolution, frame rate, &
container/codec format from an animation in my Qt3D window
(Disclaimer: I've never worked with video files before!)
As far as I can tell, Qt doesn't provide a way to generate video files
directly, so I think I have to write a series of QImages to disk and use
them to generate a video using ffmpeg. This seems like it will take a
large amount of disk space, be pretty heavy on the I/O, and generally be
slow. Are there better solutions?
If I need to do it that way though, I must generate QImages from my
existing Qt3DCore::QAspectEngine in my QWindow-derived class. I don't
see a clear/elegant way to do this.
I think I need to create an offscreen surface? window? with the correct
resolution and then somehow render & animate my scene to it, saving
snapshots as I move the camera. (I am already using QAbstractAnimation
to move the camera, so I would use it to grab the snapshots as well.)
Can I use the same root entity in multiple QAspectEngines? (i.e.
setRootEntity() to my root entity in the new offscreen and tell it to
render.)
Has anyone done this before? Is this even close to the right approach?
(I'm using straight C++ - no QML.)
Why do you want to do this in Qt when you can do it with applications
like Camtasia?
If you do want to follow this, the first part is to just generate
screenshots. There's an example app in Qt that does this:
http://doc.qt.io/qt-5/qtwidgets-desktop-screenshot-example.html.
Second, find one of the libraries that does video encoding and use your
screenshots there.
Shouldn't be too hard, but you might have to convert the pixels manually
to the video library format, so it could be quite slow.
Bo Thorsen,
Director, Viking Software.
--
Viking Software
Qt and C++ developers for hire
http://www.vikingsoft.eu
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