AVIF image orientation

[Shnatsel]

Instead of something sensible like Exif rotation encoding, they came up with a custom scheme to encode the same thing more verbosely.

Tested on sample images with https://github.com/link-u/avif-sample-images - all pass, but the tests there are non-exhaustive.

Curiously Chromium displays them correctly while Firefox seems to outright reject the sample images with orientation metadata.

Unfortunately this requires some unsafe due to mp4parse only exposing pointer API for mirroring, and I don't trust them to make a timely release since the last release was over 2 years ago.

[Shnatsel]

This is now ready to go. Please take another look - I had to use some unsafe due to mp4parse only exposing pointer API for mirroring, and I don't trust them to make a timely release with an upstream change since the last release was over 2 years ago.

[197g]

Well-motivated unsafe is alright with me and that's a possibility here. I tend to agree with the reasoning even though mp4parse does not spell out that it will return a valid, read-only pointer that isn't possibly written concurrently.

Might be worth opening a tracking issue about the outdated mp4parse releases. Are they looking for alternative maintainers? Or we evaluate newer crates (https://github.com/rerun-io/re_mp4) that also have less dependencies. But that does not need immediate attention.

[Shnatsel]

mp4parse activity is still happening in git, but releases haven't been published to crates.io in quite some time. I'm not sure what the maintenance status is.

I've opened an upstream PR for a safe wrapper today, we'll see how it goes: mozilla/mp4parse-rust#440

[fintelia]

The last published releases of mp4parse were actually at our request. My understanding is that the crate is used by Firefox which gets it from GitHub rather than crates.io