Software: VST Plug-In
This wideness analyser takes into account the difference in relative volumes of the left and right hand channels at different frequencies.
For more information, go to the Git-Hub repository
The button on the top left of the plug in switches the format to measuring total wideness and displaying that as a distance from the centre. Otherwise, in left/right mode the relative volume is displayed depending on how much louder it is at each frequency, to the right or the left of the central line.