Open gl es - How to improve performance, render to texture, blending

Question

I am here because I'm working on an OpenGL program and I have some issues with performance. I work with OpenGL ES 3.0 on iMX6 soc.

Here is my algorithm :

1. I get an image from camera which is directly map to a texture. Using an FBO, I render to texture to map the image on a specific form.

2. I do the same thing (with a second FBO) for another image which is sent via shared memory by another application. This step is performed only if the image is updated. Only once per second.

3. I blend these two textures in the default frame buffer to render the result to the screen.

If I perform these three steps separately, It works well and the screen is updated at 30FPS. But when I include the three step in one program the render is very slow and I got only 0.5FPS.

I am wondering if the GPU on the iMX6 is enough powerful, but I think it is not a complex algorithm. I think I am doing something in the wrong way, but what? I use 3 different frame buffers, so is that a good way or should I use only one?

Can someone give me answer, clues, anything that can help me? :-)

My images dimensions are 1280x1024 x RGBA. Then I am doing some conversion from floating-point texture to integer and back to float, this is done to perform bitwise operation on pixels.

Answer 1

Thanks to @Columbo the problem came from all the conversion, I work with floating-point texture and only for the bitwise operations I do the conversion which improve a lot the performance of the algorithm.

Another point which decrease the performance was the texture format. For the first step, the image was 1280x1024 but only on one composent (grayscale image). To keep only the grayscale composant and not to use too much memory I worked with a GL_RED texture but this wasn't a good idea because when I changed it to GL_RGB, I double the framerate of the render too.