Confusion about the hrd signaling options

[Selur]

Since https://x265.readthedocs.io/en/latest/ only mentions: 1. --hrd (http://x265.readthedocs.io/en/latest/cli.html?highlight=hrd#cmdoption--hrd) and 2. --vui-hrd-info (http://x265.readthedocs.io/en/latest/cli.html?highlight=hrd#cmdoption) but there are also:

--opt-qp-pps and --opt-ref-list-length-pps I wonder what these do and when they do it.

Especially since:

   --[no-]vui-hrd-info           Discard optional HRD timing information from the bistream. Default enabled
   --[no-]opt-qp-pps             Discard optional HRD timing information from the bistream. Default enabled
   --[no-]opt-ref-list-length-pps  Discard optional HRD timing information from the bistream. Default enabled

is totally confusing! Shouldn't this be more like 'Discards optional HRD timing information from the bistream, when disabled.'

I guess: 1. unless vbv is used hrd does nothing 2. when hrd is disabled vui-hrd-info, opt-qp-pps and opt-ref-list-length-pps do nothing 3. when hrd is enabled, vui-hrd-info allows to enable/disable that vui hrd infos are written 4. when opt-qp-pps is disabled opt-ref-list-length-pps does nothing 5. when opt-qp-pps is enabled opt-ref-list-length-pps enable/disable whether some additional infos are written

=> would be nice if there was some documentation and someone could clear up how these options interact.

[Pradeep Ramachandran]

Sorry, this was a documentation error. The help menu was a copy-paste error, and we forgot to update the online documentation. It is fixed now. opt-qp-pps and opt-ref-list-length-pps optimize the values of the QP and ref list length that is sent in the PPS. the vui-hrd-info and the vui-timing-info can be used to control optional HRD and timing info that is sent in the PPS.

Hope this clarifies things. Please let us know if you require any further clarification

[Pradeep Ramachandran]

Did the fixed documentation address your concern? Can I close this issue?

[Selur]

Yes, that helped. Thanks, issue can be closed from my end. :)