Metadata OBUs being written without trailing bits

[jamrial]

An encoding like rav1e INPUT --mastering_display "G(0.1,0.2)B(0.3,0.4)R(0.5,0.6)WP(0.7,0.8)L(2,1)" --output OUTPUT results in the Mastering Display metadata OBU missing the trailing one bit, plus any potentially required trailing zero bits to align to the next byte.

The spec in https://aomediacodec.github.io/av1-spec/#general-obu-syntax states that any OBU type except Temporal Delimiter, Tile Group, Tile List and Frame must include the trailing bits.