My idea would be something like (sketch):
main.cpp:
#include <QGuiApplication>
#include <QQuickView>
#include <QObject>
#include <QMutex>
#include <QVector>
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
auto view = new QQuickView;
view->setSource(QUrl::fromLocalFile("test.qml"));
view->show();
// I use a QVector here, but you would have your AVFrame and
// its allocated memory buffer..
QVector<unsigned char> buffer;
QMutex mutex;
QObject::connect(view, &QQuickView::afterRendering, view, [&]() {
mutex.lock();
buffer.resize(4 * view->width() * view->height());
glReadPixels(0, 0, view->width(), view->height(), GL_RGBA,
GL_UNSIGNED_BYTE, buffer.data());
mutex.unlock();
}, Qt::DirectConnection);
return app.exec();
}
test.qml:
import QtQuick 2.2
Rectangle {
width: 1920
height: 1080
Rectangle {
width: 500
height: 500
color: "green"
anchors.centerIn: parent
RotationAnimation on rotation {
from: 0
to: 360
duration: 2000
loops: Animation.Infinite
}
}
}
I don't know whether this would work for you.
Elvis
Den tis 13 juli 2021 kl 15:31 skrev Nuno Santos <nuno.san...@imaginando.pt>:
>
> 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
>
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