HRD=1 fails

[TEB]

hi! Im trying to force x265 to enable HRD info in my encodes. My packager requires it.

Using this string:
"ffmpeg -i source.mp4 -pix_fmt yuv420p -codec:v libx265 -x265-params rc-lookahead=50:keyint=100:min-keyint=50:hrd=1 -preset slow -crf 20 -force_key_frames "expr:eq(mod(n,50),0)" -c:a copy -y test1.ts "

Packager complains about no HRD info
Mediainfo shows no_hrd

I get this warning from libx265: x265 [warning]: NAL HRD parameters require VBV parameters, ignored

How do i interpet this one ? Why do i need a vbv buffer defined when i only need the information so that the packager can understand the bitrate in the ES

/TE