Don't know who needs this, but I recently learned a lot of _stuff_ about YUV/chroma downsampling stuff and how the color meta data in video material works. So I braindumped a big part of that here
https://github.com/rerun-io/rerun/blob/8dcb2f4eb6339a16aa17cb22efca78ec729ca95e/crates/store/re_video/src/decode/mod.rs#L4
(edit: fixed link. this wasn't a long lived branch)
maybe this will become a blog post 🤔