Help with advanced conditional filtering needed

[scharfis_brain]

I have a frame sequence as follows:

A A B B bc C cd D de E E F F fg G gh H hi ...

I want to decimate this thing by two, but in a very special way:

for the duplicates, it is clear: return one of them
(btw: those duplicates are 100% copies of each other, so AVGLuma is indentical)

but the blends aren't identical.
so I want them decimated, too, but they should be decimated by blurring two blends together!

this means, the returned video should look like this:

A B bcC cdD E F fgG ghH hi...

I am not able to make an frameevaluate script out of that

the condition is, to simply compare two following frames on equality an then either return one of the dupes or if that condion fails a mix of two consecutive frames
so that I only have half of the frames left behind.

[stickboy]

What about running Dup with its blending mode and then decimating afterward?

Depending on how consistent the pattern is, you might be able to do something like:
Overlay(SelectEven(), SelectOdd(), opacity=0.5)but that wouldn't handle the de case in your example. Hmm...