Newb question: Apply color filter to only half the frame? Edit plugin source?

[Megatron42]

Hello, first time poster, long-time user (for basic re-encoding purposes).  Big fan of the app and the new revamp!  I'm now using Avidemux 2.6.5 (r8936) under Ubuntu x64.

Anyway, I have a question about filters.  I have obtained a 3D side-by-side rip where the color of one half of the image does not match the other.   The video works on the 3D TV just fine, but the color discrepancy causes all the elements in the scene to have a "shimmer" since the eyes cannot agree on what color anything is.  The "MPlayer eq2" filter under Colors is good for the job, but as expected it applies the correction to the entire frame.  Is there a "meta-filter" that restricts a filter's processing to just half the frame?  Or is it possible to create a custom version of the filter?

Thanks in advance!

EDIT: Also I'm looking for the source for Mplayer EQ2 but it doesn't seem to be included in the source package.  Can someone point me to it?