[I originally filed this issue in https://crbug.com/aomedia/2793.]

What version / commit were you testing with?
(git describe can produce this info.)

AV1 Bitstream & Decoding Process Specification
Last modified: 2019-01-08 11:48 PT
Version 1.0.0 with Errata 1

In Section 6.4.2. Color config semantics, the last table describes the chroma sample position name CSP_UNKNOWN as:

Unknown (in this case the source video transfer function must be signaled outside the AV1 bitstream)

It is not clear why the "source video transfer function" is mentioned. Should that be changed to "chroma sample position"?