CCE mutipass CBR Why is this needed

[gavo]

If cbr is constant how can makeing a pass help move the bitrate up and down if it stable to begin with.

[tigerman8u]

Look and see if the multi-pass check mark is greyed out when check cbr

[kolak]

According to CCE manual:

"In CBR mode, the more passes will result more constant and stabler
bit allocation for GOPs, and also the bit allocation for each picture
in a GOP will have been modified to achieve the higher quality of
image."