Maybe too slow for you, but ARM is rapidly becoming more and more prevalent as ARM chips can occupy an interesting quadrant on the power / speed curve. I imagine with thorough assembly optimization a modern ARM server CPU could outperform a modern x86_64 CPU in terms of efficiency.
If this wasn't the case we probably wouldn't see AWS, Apple, and Microsoft all investing in their own ARM silicon.
Granted, HEVC compression is a very specific use case
