Comment by cogman10
5 hours ago
That was one of the best decisions of AOMedia.
AV1 was specifically designed to be friendly for a hardware decoder and that decision makes it friendly to software decoding. This happened because AOMedia got hardware manufacturers on the board pretty early on and took their feedback seriously.
VP8/9 took a long time to get decent hardware decoding and part of the reason for that was because the stream was more complex than the AV1 stream.
Hmmm disagree on your chain there. Plenty of easy hardware algorithms are hard for software. For example, in hardware (including FPGAs), bit movement/shuffling is borderline trivial if it's constant, while in software you have to shift and mask and or over and over. In hardware you literally just switch which wire is connected to what on the next stage. Same for weird bit widths. Hardware doesn't care (too much) if you're operating on 9 bit quantities or 33 or 65. Software isn't that granular and often you'll double your storage and waste a bunch.
I think they certainly go hand in hand in that algorithms relatively easier for software vs previously are easier for hardware vs previously and vice versa, but they are good at different things.
I'm not claiming that software will be more efficient. I'm claiming that things that make it easy to go fast in hardware make it easy to go fast in software.
Bit masking/shifting is certainly more expensive in software, but it's also about the cheapest software operation. In most cases it's a single cycle transform. In the best cases, it's something that can be done with some type of SIMD instruction. And in even better cases, it's a repeated operation which can be distributed across the array of GPU vector processors.
What kills both hardware and software performance is data dependency and conditional logic. That's the sort of thing that was limited in the AV1 stream.
All I read about is that it's less hardware friendly than H.264 and HEVC, and they were all complaining about it. AV2 should be better in this regard.
Where did you read that it was designed to make creating an hardware decoder easier?
It was a presentation on AV1 before it was released. I'll see if I can find it but I'm not holding my breath. It's mostly coming from my own recollection.
Ok, I don't think I'll find it. I think I'm mostly just regurgitating what I remember watching at one of the research symposiums. IDK which one it was unfortunately [1]
[1] https://www.youtube.com/@allianceforopenmedia2446/videos