OpenGL ES Texture streaming or mapping

Question

Situation

I have a video stream coming from a native library in iOS. I'm trying to display the image in an iPhoneOSGameView using glTexImage2D and glTexSubImage2D for updates. I can update subregions of the image, I receive a structure that tells me which rectangle has to be updated on the gpu.

The issue

Framerate is quite low. After much profiling both in OpenGLES and the application code, I have concluded that the application usually is waiting on the texture upload. The slow function is glClear , but I suspect there's an intrinsic glFlush in there.

My question

I've seen some people talking about glMapBuffer that could allow me to stream the video directly to the texture in user-space. I've looked at pixel buffer objects, but they require OpenGLES 3.0 or an extension in 2.0. Is there an efficient way (for mobile) to stream a texture with minimal memory copying OR a way to transfer the texture from different thread?

Additional information

I'm working in C# Xamarin and I'm testing on different devices such as an iPod Touch Gen3, a iPad Air 2 and a iPad Pro 12".

Answer 1

there an efficient way (for mobile) to stream a texture with minimal memory copying

Most operating systems have some media framework which allows import of images directly using the EGL_image_external extension avoiding the need to upload. I'm not sure how it works on iOS, but I strongly suspect it should be possible. It's OS-specific unfortunately, so no standard way of doing it.

OR a way to transfer the texture from different thread?

Just create two GL Contexts in the same share group.

https://developer.apple.com/library/ios/documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/ConcurrencyandOpenGLES/ConcurrencyandOpenGLES.html