Christophe Ducommun who keeps optimizing Snow Leopard for his application MovieGate just sent us results to illustrate how Snow Leopard can improve performance when one can make use of Grand Central and Open CL. Tests below have been performed with a Mac Pro 2007 (Quad Core 2.66 GHz with a GeForce 8800 GT).
150 frame/s for encoding in MPEG-2
70% CPU load for decoding
130% CPU load for MPEG-2 encoding (ffmpeg)
104 frame/s for encoding in MPEG-2
165% CPU load for decoding
100% CPU load for MPEG-2 encoding (ffmpeg)
The overall gain is around 50%, a rather impressive improvement without changing any component on the hardware. It illustrate how much unused power one can have in hardware, decoding being more GPU demanding than encoding. So, optimization is a powerful strategy, even though the balance between CPU and GPU is not always trivial.
This is a very promising result illustrating how Grand Central and Open CL can boost performance, and why developers should invest a bit of time is taking advantages of those technologies.