This, perhaps? <a href="https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;draft-grange-vp9-bitstream-00" rel="nofollow">https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;draft-grange-vp9-bitstream-00</a><p>It&#x27;s only a draft, and two years out of date, but it is public.