Set target quality level (CQ) for HEVC_Nvenc encoder

The hevc_nvenc encoder supports constant quality mode ( -cq parameter ) for VBR rate control. It offers better quality than 2 pass VBR and gives better perceived quality than CQP at the same bitrate.

From ffmpeg -h encoder=hevc_nvenc :

-cq <float>  E..V.....   Set target quality level (0 to 51, 0 means automatic) for constant quality mode in VBR rate control (from 0 to 51) (default 0)

It would be nice if you could add this option! Thank you!