* -k full bandwidth Tells the encoder to use full bandwidth and to disable all filters. By default, the encoder uses some highpass filtering at low bitrates, in order to keep a good quality by giving more bits to more important frequencies. Increasing the bandwidth from the default setting might produce ringing artefacts at low bitrates. Use with care!
I think that this encoder version was the last to allow the use of the -k switch.
but, what about if we use the cbr 320 bitrate ?
Why would its being CBR make any substantial difference to this fact?