On Fri, 24 Aug 2001, Josh Huber wrote:
> Thanks for the tips. I'll see what I can do this weekend... > > > Inverse Discrete Cosine Transform (or Integer?) > > I guess I was more asking what it's role in mpeg decompression was... > The same as its role in JPEG compression: you take the DCT of an 8x8 block of pixels in the image, and quantize the result by using fewer bits to express each coefficient. Decompression just reverses the process of compression; you extract DCT coefficients from the datastream and do an IDCT. A motion compensation step is also a part of the process, but I'm less familiar with that. Now, I think you need around 500 floating point-operations to compute an 8x8 IDCT (I believe the actual figure is something like this.). DVD video is 720x576, so you'd need to sustain around 100 megaflops/sec in the IDCT alone to be able to play video smoothly. Based on that figure, I think software-only decoding *might* possible on a 500 Mhz g3, but it'd have to be pretty tightly optimized. It'd be nice if ATI would release documentation on the hardware IDCT and motion comp features of the Rage 128 chip... --Peter
