We are basically trying to use compressed textures in OpenGL and create texture atlases (collecion of textures) for which we need to use the glCompressedTexSubImage2d API. We have been trying to get it working for quite a few days now but by the looks of things that function does nothing.It does not copy any pixels to the texture that is successfully initialised using glCompressedTexImage2d. Basically it looks like its not supported. The only thing we have found online is a few posts by developers saying that glCompressedTexSubImage2d doesn't work on the arm opengl es3 emulator but the posts look a bit old, something like one two years old so we thought it might have been fixed by now. Does anyone have any information regarding this API call?