Long-GOP formatted encoding means that there are conplete frames recorded every so many frames of video ... between 9-32, typically. Though I've seen longer. These are called "i-frames".
In-between, all that is recorded to disk is a matrix file of pixels that
- will change before the next i-frame.
- have changed since the previous i-frame.
- BOTH.
So to decode and play this, or encode it to a new file, the system has to create several frames and work them as a group. It's not simply going down the clip decoding frame after frame or encoding frame after frame sequentially. It's far more complex a computing task.
It makes a smaller file though, AND ... specialized chips can be manufactured to do this as their only task. Which is why the camera makers love long-GOP. They can 'smallify' files real fast.
But it's absolute HADES to the computer when editing it. Because of all the extra computational work required.
QuickSync is a hardware chip built into some CPUs that is an attempt to do the same process as the one done by the chip in the cameras. However ... QuickSync by nature is a generalized H.264 tool, and won't be exactly the equal thing that the camera chip is. So it's fast ... but not always as accurate as you might like.
"Software only" in the render/export process refers to using the CPU standard processing tasks to compute the long-GOP data. Which is slower, but typically more accurate.
Some GPUs now even have some long-GOP capabilities. So ... it's complicated. Some CPUs, some GPUs have long-GOP chips in them. They each have slightly different capabilites and processes.
The best one around 'here' at 'splaining all this exactly per hardware bit is @RjL190365 ...
Neil
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