> I stick with h264 for the most part because h265 encoding requires far too much extra compute relative to the space savings. I can spend an hour compressing a file down to 1gb with h264, or I can spend 12 hours compressing the same file to 850mb with h265.

FWIW, as someone who is a complete layman on this topic but has spent much of the past 6 months converting age-old videos to h265...

i have a pi5 where i queue up old videos into a RAM disk, it converts them to h265, and moves them back to the machine which uploaded them. It can take up to 2 days to compress any given video (depending mostly on the input format - old AVIs tend to compress in a few hours), but the space savings is _much_ higher than what you're reporting. The average size of my h265-encodes is anywhere from 1/3rd to 1/2 of the original, and 1/4th of the original is not terribly uncommon. That said: the input formats vary wildly, with possibly only a minority fraction being h264.

i've tried the same thing using a pi4 but it needs roughly 4-5x as long as the pi5. An 8-core intel-based laptop can do it in some 25% of the time of the pi5 but pulls a lot more electricity while doing so. So my otherwise idle pi5 gets the assignment.

My Firefly collection (14 tv episodes plus the movie) dropped from 8gb to 2.1gb. My Bob Ross collection (141 videos) went from 38gb to 7.4gb. 128 Futurama episodes/movies was cut from roughly 50gb to 21gb.

i was once asked why i didn't choose AV1 and the answer is simple: when i googled along the lines of "how to get the best video compression with ffmpeg" the most common answer was h265. Whether that's correct or not, i can't say, but it works for me and i've freed up the better part of a terabyte of space with it.