Hello Nuno
Not sure if it helps, but the book Anton's OpenGL 4 Tutorials has a chapter
about recording a video from OpenGL. It's the same approach you are doing,
saving images from a frame buffer at certain fixed rate. I just dont know what
kinf of optimisations are done, I didnt read it with much attention.
CheersJoão
Em terça-feira, 13 de julho de 2021 14:33:42 GMT+1, Nuno Santos
<nuno.san...@imaginando.pt> escreveu:
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
_______________________________________________
Interest mailing list
Interest@qt-project.org
https://lists.qt-project.org/listinfo/interest
