Media Encoder reduces CBR on software mode
When encoding in software mode at 40 Mbit/s CBR, the encoder roughly halves that number (20,3 Mbit/s) even though it should be set to 40 Mbit/s.
When doing the same thing using the hardware encoder, the bitrate is a solid 40 Mbit/s.
This seems like a significant bug, particularly when encoding 4K video, since the hardware encoder can't handle bitrates above 60 Mbits/s.
Antoine (Autokroma.com) commented
Could you try AfterCodecs ? https://autokroma.com/AfterCodecs/