Yet another "not sure if this applies, but..." Maybe take a look at what QRenderCapture is doing in Qt3D? It allows you to capture a QImage per frame, so it might have some of the bit processing/manipulation you're looking for.
I'm using it to capture video by saving images to a temp dir and then processing them using ffmpeg. I use QtConcurrent::run() to do image processing (e.g. adding an overlay) & writing so it doesn't affect the main thread doing the capturing. --- Andy Maloney // https://asmaloney.com twitter ~ @asmaloney <https://twitter.com/asmaloney> On Tue, Jul 13, 2021 at 9:32 AM Nuno Santos <nuno.san...@imaginando.pt> wrote: > Elvis, > > Thanks for sharing your thoughts. It makes sense. > > I need to dive into the toImage function, try to read directly the bytes > from the FBO and see if that has any performance impact. > > Best regards, > > Nuno > > > On 13 Jul 2021, at 14:10, Elvis Stansvik <elvst...@gmail.com> wrote: > > > > Hi Nuno, > > > > I'm really out of my waters here, but, provided you don't need to hold > > on to each AVFrame after you are "done with it", you could perhaps > > avoid having to allocate a QImage for each frame (which toImage forces > > you to do) by just allocating a a single AVFrame and a single memory > > buffer for it, and then do what toImage does, which is make sure the > > FBO is bound and read the pixels off of it with glReadPixels. Then you > > could read the pixels straight into the memory buffer used by your > > AVFrame. > > > > That way you would save the overhead of a new QImage being allocated > > each time, which might speed things up..? > > > > Just ideas here. Have not worked with GL or ffmpeg before. > > > > Elvis > > > > Den tis 13 juli 2021 kl 11:22 skrev Nuno Santos < > nuno.san...@imaginando.pt>: > >> > >> Hi, > >> > >> I’m trying to capture the content of an FBO to a video file. This video > file should contain the animations generated by a qml scene. > >> > >> To do this, I’m recurring to QOpenGLFramebufferObject class toImage() > method. > >> > >> My scene is being drawn at 1920x1080. Each call to toImage takes 30 ms! > :( > >> > >> If I want to render to file at 60 fps, ideally, this call would need to > take less than 16 ms to give me room to do other operations, such as video > encoding and the actual render. > >> > >> As anyone been here before? What other strategies are available to copy > the FBO data to an image? > >> > >> I’m using libav to encode the video file, therefor I need to fill an > AVFrame. Right now I’m filling the AVFrame from the QImage generated by the > FBO toImage method. > >> > >> Does any one knows a method of filling an AVFrame directly from texture > data? > >> > >> Thanks > >> > >> Best regards, > >> > >> Nuno > >> _______________________________________________ > >> Interest mailing list > >> Interest@qt-project.org > >> https://lists.qt-project.org/listinfo/interest > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > https://lists.qt-project.org/listinfo/interest >
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