[m463]

I'm not a video expert, but one thing I've noticed is that there seems to be a lot of discrepancies between video files and the way programs use them.

I think it might be differences between how the the container describes the video and the video itself, and which one is chosen as the truth during operations.

[freeone3000]

the "video itself" doesn't really exist. If you're on Windows and use MPC, you can test this yourself - use WMV9 as a renderer, take a PNG screenshot, then switch to NVENC, and take a screenshot at the same timestamp. You'll notice that on most videos, the screenshots are not the same (with NVEnc introducing macroblocking in darkness, which WMV9 gradients out properly). Using the rendered video as a source of truth instead of the source material itself would be as big of a mistake as using Photoshop on a JPEG.