Okay, you got the wrong idea about 2pass encoding in regard to NVEnc. 
a. NVEnc does no 2pass like x264&co which optimized to hit a specific bit rate. (running 1 pass to analyse, running a second pass to hit a specific bitrate)
b. what multi pass for hardware encoders do is they recompress the source image once and then another time while trying to optimize the compression.
but .. this is a 1pass process, the encoder is not reading the source multiple times. It is something completely different than 2-pass encoding with x264&co.
To lessen the confusion about this, I separated this into two options. (forgot to adjust the 'encoding mode' tool-tip)
Cu Selur
a. NVEnc does no 2pass like x264&co which optimized to hit a specific bit rate. (running 1 pass to analyse, running a second pass to hit a specific bitrate)
b. what multi pass for hardware encoders do is they recompress the source image once and then another time while trying to optimize the compression.
Quote:In 2-pass rate control modes, NVENC estimates the complexity of the frame to be encoded and determines bit distribution across the frame in the first pass. In the second pass, NVENC encodes macroblocks in the frame using the distribution determined in the first pass. 2-pass rate control modes can distribute the bits more optimally within the frame and can reach closer to the target bitrate, especially for CBR encoding.source: https://github.com/rigaya/NVEnc/blob/mas...ass-string
but .. this is a 1pass process, the encoder is not reading the source multiple times. It is something completely different than 2-pass encoding with x264&co.
To lessen the confusion about this, I separated this into two options. (forgot to adjust the 'encoding mode' tool-tip)
Cu Selur