PVR textures versus PNG in OpenGL ES

Question

I'm developing a 2D application for the iPhone that renders lots of textures. Most of them are loaded from PNG files with alpha transparency at the moment. As a test I've been playing around with PVR-testures as well to see if there is any performance difference.

The PNG-textures are loaded with the Texture2D class that came with the crash landing example. The PVR-testures are loaded with the PVRTexture class from the PVRTextureLoader example. I create the PVR textures using Apple's texturetool.

As a test I render a background (512*512) and on top of that 36 90*64 pixel sprites (from a 512*512 texture) with transparency. PVR textures renders at around 58 fps and the PNG at 47 fps. Is this what I can expect or should the difference be bigger? Also, the textures generated by texturetool looks really bad, is the PVRTexTool better?

Answer 1

Performance should be better with the PVRTC textures, as they are compressed (lossy). The decompression is done in the graphics hardware itself. Less texture data is being transferred around, so you get more bandwidth. The price you pay for the RAM and bandwidth saving is the loss of quality.