HEVC+ffmpeg = files with slower preset larger than media preset.

[rgr]

First try to encode to x265 with the latest ffmpeg and it comes out that the "slower" preset generates a larger file than the default...


[Attachment 65456 - Click to enlarge]

[LigH.de]

A slower preset spends more time searching for similarities in the video. That doesn't guarantee it can actually find a way to encode the video content with less data. Some slower presets enable the use of algorithms which may save some space in the average case but may as well need more space than more simple algorithms in the worst case for them.

[davexnet]

The larger size on the slower presets has been mentioned a few times
in this forum, this seems to be the way it works in X265

[jagabo]

Like x264, x265 enables settings that give better image quality (and require more bitrate) as you go to slower settings. So moving to slower presets doesn't necessarily mean you will get more compression.