You can also use DMA to miss out the processor if the hardware will allow it. That speeds things up.
You can also use buffering software to read ahead. Some buffering software will also do error correction as well.
I used to have a DVD/MPEG decoder card which used to really do the buisness. You put the DVD drive through it and it then did the graphics. It really did rock. Alot of high end graphics cards have decoders built into them
I think it was a Creative labs Dxr2 a brief search seems to say its not supported any more.