I've been transcoding my media collection leaving my PC on overnight over months, it's great. My biggest issue is client support for native playback of AV1, naturally.

For what it's worth, AB-AV1 [1] is a pretty awesome tool written in rust which compares random samples from a file at different parameters based on their VMAF score [2] (algorithm from Netflix for human-perceived visual likeness), choosing optimal parameters to save as much space as possible with the loss you're willing to stomach, on a file-by-file basis.

Small plug: I made a nice little python GUI wrapper for ab-av1 [3].

[1] - https://github.com/alexheretic/ab-av1 [2] - https://github.com/Netflix/vmaf [3] - https://github.com/Loufe/AB-AV1-GUI

Because of conversion losses, I have to imagine this is subtly very bad.

Every form of lossy compression deleted data. Yes AV1 is more efficient but only when working off of high quality originals.

H265 already deleted a ton of data. It can never recover the quality loss. Compressing even further can only worsen the image.

Aside from video, audio compatibility is tricky as well. You can do AAC stereo and most things support that but AAC 5.1 seems to be supported by only some devices so all my video files end up getting stereo AAC, 5.1 AAC, and 5.1 DTS to avoid live transcoding.

I personally use av1an, and use VMAF target quality of 95 to 96. It's been really good and fast.

https://github.com/rust-av/Av1an

I'd be surprised if there's any noticeable difference between 265 and AV1 when coming from the 265 encoding. 265 has already thrown a lot of stuff away, so there's not much for AV1 to work with.

Maybe if you're going to a lower resolution it would be fine (ie: going from 4k 265 to 720p AV1).

Do you know what plex clients can handle av1 without the server having to transcode?

I started looking into converting stuff to AV1 but only confirmed that my gpu doesn't support AV1 but does support hevc so I stopped there...

What is the difference in size of files? Around?