Introducing the Enhanced Broadcasting Beta
blog.twitch.tv
We’ve partnered with NVIDIA and OBS to add Enhanced Broadcasting to OBS. Enhanced Broadcasting provides two critical capabilities — multiple encodes and automatic configuration.

In addition to giving streamers more control, this beta paves the way for future improvements such as new codec support, and experimenting with HEVC and AV1. AV1 is the next generation of video encoding technology — 40% more efficient than the current AVC standard — and it will improve visual quality, and reduce bandwidth.

Also: https://blogs.nvidia.com/blog/twitch-multiencode-av1-livestreaming/