FFMPEG slows down over time

[bradwiggo]

FFMPEG seems to slow down as it goes along processing a video. I was processing a video for about 10 minutes and it started out at about 3x speed and went down to about 2.5x by the end.

Specs:

i5-8600k
16GB RAM
2070 (although wasn't using GPU)
On an SSD

Seems to happen with any kindof script or instruction.
Isn't a CPU heat issue, never goes above 60 degrees and drops to 30 degrees 2 seconds after the program is finished.

Edit: Just noticed something else: it slows down a lot in the first 10 or so seconds. So it might starts at 10x and rapidly drop to 3.2x, and then it will slowly drop once it gets there.

Edit 2: Happens in Handbrake too. Don't have any other video programs to test really.

[davexnet]

Something else in the PC competing for the CPU?

[bradwiggo]

Something else in the PC competing for the CPU?

No CPU is about 1-4% before starting it.

[pandy]

This can be normal - prediction of speed depends on overall complexity - at the end prediction is close to real...

[pm-s]

It's either video complexity rising or thermal throttling