[the8472]

The maximum number of references frames, i.e. how much the Decoded Picture Buffer has to hold, is 16. So even if a GOP is 1 minute long you would have to hold at most 16 pictures in memory to have enough information to stream over that 1-minute segment.

So I still do not see how this would prohibit parallel processing.

[pedrocr]

Not sure how that would work. You have a thread that's decoding the frames 1 minute in front of where playback is, so if you're not decoding full frames and storing them until you need to display them what is that thread doing?

[the8472]

transcoding or video editing in slices is a common application.

you cut the video into a handful of parts at keyframes, process the parts individually in a streaming manner and then splice the partial results together.

If we're talking about playback then creating seeking-thumbnails could similarly benefit from parallel processing.