force transcode to av1

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It's quality for bitrate and AV1 wins almost every time, save for a few niche cases..

https://imgur.com/a/61fyhgf (purple line is QSV AV1 10Bit Quality output vs QSV  H265 10Bit Quality on Intel Arc)

I don't think there's enough info here to make the claim you've made but I'm also just getting into my own investigations. For *encoding* AV1 wins, hands down. On the fly is a different use case, however. Hardware encoders for AV1 are limited right now and my experience is zero as my A380 is still in the box waiting for me to get home from a business trip. This graph is an isolated use case without resolution, parameters, etc... or an attempt to limit what bias might be there. It may be correct data for 1080p 10-bit SDR at constant quality or something similar. 

But when you take into account something like the flexibility of de-noising/film grain synthesis of AV1, the excellent compression you can get on 4K HDR or SDR content, the difference in how you approach the encoders versus x265, it becomes a little bit of a different ballgame and it's hard to compare apples to apples. It's also true that if you're looking to have 4K DolbyVision content, AV1 isn't your codec (yet?).

I guess I concede your main point that it's too early to really say, on the topic of transcoding, which codec wins the day. But with AV1 being new-ish, having very little support on the hardware encoding front, and still producing those pretty impressive results in comparison to a codec that has been around for an extremely long time, it seems like AV1 is without a doubt the direction of streaming media in the future.