[rav1e] Expose the speed setting about libavif HOT 3 CLOSED

Alright, I talked with the libaom team, and this is pretty close to how it'll operate in the next version:

4bf0187

I might tweak the libaom speed implementation next week at some point, but this API is pretty friendly and reasonable. Thanks for the suggestion; I think it is a winner.

from libavif.

It looks like that 0-10 speed is shorthand for these settings:

https://github.com/xiph/rav1e/blob/master/src/api/config.rs#L334

I don't want to prematurely just jam in a 0-10 "speed" dial on avifEncoder that only works on rav1e, if there is a better way to expose these features, or if there is a way to simulate these same 0-10 values in libaom (and/or SVT in the future, etc).

I'm on board with such a feature, I just want to make sure the values in avifEncoder make sense to more than one codec, if I can help it.

from libavif.

Makes sense, though it may be tough to generalize these settings, as different encoders may implement different sets of optimizations. How about having a simple proxy for this in avifEncoder, for example a speed integer between 0 and N, and then map that setting in different ways for different encoders?

For example, for rav1e we would just map avifEncoder->speed (in [0-N]) to rav1e's speed setting (in [0-10]), while for other encoders we could use a different strategy (enabling or disabling some features based on the speed value).

This is pretty much already what we do for quantizer: we have a quantizer setting in libavif in the range [0-63], which then gets mapped differently depending on the codec (for instance, we map that to [0-255] for rav1e).

from libavif.