When Apple deployed support for HEVC in 2017, all devices that supported iOS/tvOS 11 or macOS High Sierra gained the ability to play HEVC video (some via hardware, some via software). Something very similar will happen when Apple deploys AV1 support.
The old Apple TV got 4k 60fps VP9 decode in Youtube from A12 onward, and the AV1 software decoder is roughly similar in load, so 4K should be doable.
Wouldn't be surprised if the old one was already using AV1 for Youtube.
edit: there are 3rd party apps for the Apple TV that play back VPR and AV1 in software, this thread suggests that even on the old hardware, AV1 decoded better:
> 4k HDR @ 60 fps encoded with AV1 - Plays much better than previously, there are still some frame drops in more complicated scenes (for example when they show palm tree on a beach in Costa Rica video). Unfortunately it does not trigger HDR mode on my TV (all other HDR and Dolby Vision content does it correctly).
> 4k HDR @ 60 fps encoded with VP9 - It works, but performance is not as good as AV1. Does not trigger HDR mode on my TV. More dropped frames, video can freeze (audio plays, but picture is frozen).
Worth noting that Youtube often has lower relative bitrates/quality levels than other uses.
Right I think this is a point many miss. Most Apple HW can do AV1 decode in SW plenty fast, it's just much more energy than with a hardware decoder (big deal for phones in particular). What's really missing is the SW support, but I'm delighted to hear that it's _finally_ going to happen.
To be fair the A series chips are very powerful (compared to something tiny like a Roku stick) and don’t have the thermal/power limitations of an iPhone. They may be able decode VP1 at full speed without VP1 specific hardware.
I don’t think YouTube will abandon VP9 anytime soon either though. They want AV1 for improving quality and lowering bandwidth - but VP9 and MPEG before it will stay a long time yet.
Given that they average 2-3 years between releasing updates, that sets back AV1 a while longer.
There's a chance it'll have enough grunt for software decoding, perhaps at 1080p but not 4k (speculation).