So, what’s so good about ProRes and DNxHD?
What’s good is that they don’t compress the video as much. They trade storage space and bitrate for quality and ease of processing. They typically need ten times as much storage. That’s a lot, but hard drives are tending towards being free, so it hardly matters these days.
In fact, ProRes and DNxHD (sometimes called “intermediate” or “production” codecs) sit in a kind of “sweet spot” between the humongous data rates of uncompressed video, and the egregious processing demands of Long Gop video.
Why not just work with uncompressed?
Because you need as much as six times more storage and data bandwidth than you do with ProRes and DNxHD. Even with disk prices as low as they are, that’s asking a lot. Moreover, you’ll find yourself unable to process as many streams of uncompressed video in real time: you’ll hit a brick wall once your disk system maxes out. ProRes and DNxHD are so processor-friendly, that even though your computer has to uncompress multiple streams on the fly, you’ll probably find you can edit more simultaneous streams than with uncompressed.
But what about quality?
Both ProRes and DNxHD are effectively “visually lossless” at their higher bitrates. That means exactly what it says: you can’t tell the difference between your original video and the same material encoded to ProRes or DNxHD.
So you don’t need to worry about generation loss. In fact, you can usually make many copies in the intermediate codec format without any apparent degradation.
It’s worth stressing that the main reason for ProRes and DNxHD’s increased quality is that they are not long-GOP codecs
Once you’ve converted, your edits will fly. These codecs are so efficient that you can play multiple streams with a fraction of the effort you need for a single stream of H.264 - based video. As an example, on my Macbook Air, playing any HD Long-Gop clip will cause the fan to come on at full power within seconds, but with ProRes, I can play a clip - in much higher quality - with no sign of the fan.