Video Rendering questions

[vaconcamp]

Something that has always bothered me was the time it takes to render a 2d video. Now I've seen computers do some crazy things in real-time, but when it comes to video rendering, it's surprises me how slow it can be. I can understand why 3D rendering takes a long time, but when a computer renders a video isn't it just replacing the pixels of the original video in the background with the new ones you added?

 

[Sunius]

Yes, but video rendering is most usually done by the CPU, which isn't very fast when compared to GPUs (it's around 50 times slower).

 

[PhilFrisbie]

Yes, the previews are handled in hardware, but generally the final rendering is done in software with the CPU.