What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit?
Can you repeat the problem? If so, what are the steps?
I’m trying to save a preset using the hevc_nvenc encoder with the Constrained VBR rate control. When I go to save it, it reverts back to Constant Bitrate. It seems to be just this particular encoder that doesn’t save correctly as far as I’ve seen.
Can confirm this happens both with nvenc and qsv variants of avc/hevc.
Also when using constrained VBR for regular codecs (tested x264 and x265) the crf value is not saved, it uses the default (23 for x264, 28 for x265) when trying to use the preset.
These are fixed for the next versions except qsv (Quick Sync Video) where it is not implemented because I have not figured out how to map it and not hinder compatibility. Not related to CVBR, but for another example,
Basically, with respect to “map” for QSV, if you setup CVBR and manually add a line to Shotcut’s Other tab: qscale=31; it ends up doing CQP (constant quality) when you check the log. Intel has many rate control methods with compatibility pitfalls making it difficult to map to common methods and access through FFmpeg parameters.