I'm using ffmpeg on the command line to encode video from a QuickTime ProRes 4444p DCI-resolution source to h.265, y420p. It's working just fine, but I noticed something very odd: If I change nothing but the preset, the file size goes down as the encoding speed goes up:
Preset and resulting file size:
- veryslow: 5814379
- slower: 5812081
- slow: 5640739
- medium: 5455779
- fast: 5164506
- faster: 5099833
- veryfast: 5108824 (file size starts going up from this point)
My question is: This is rather the opposite from what I'd expect. Am I missing something obvious?