Deleting every frame between equal frames in video

[StainlessS]

Not sure, I think you need 32 bit VDub (I still use XP32, and will continue to after APRIL 8 [when
dropped from Ms support, I think])

I see no reason why windows Media player should not open the script, although it would just seem to hang
until script comleted.

Should be able to open avs script containing only eg:

return Colorbars()

Yes, it looks like you have Avisynth v2.58 installed, I think many of the DebugView messages
are coming from v2.58 eg "CAVIStreamSynth::QueryInterface()" messages, v2.58 was I think complied
with debug logging enabled.
I use v2.6, might be beter choice than v2.58, despite it being alpha, is more stable than v2.58, IMHO.
If you set DebugView filter (EDIT menu), to only display lines with a colon (':') then it would only
capture relevant messages (mostly), I nearly always use a colon in debug messages.

yep, you were correct, FrameSel v2.12, not v1.12 (my mistake).
However, it may be that you installed v2.6 plugin (for Avisynth v2.6) and so Avisynth cannot find it.
(Avisynth v2.6 can load v2.5 plugins but Avisynth v2.58 cannot load v2.6 plugins).
In the folder named 'Avisynth25' not 'Avisynth26' unless you change to Avisynth v2.6Alpha5.

Looks like we are dropping way too many frames

DropDupSequences: Dropping 18526 of 18785 frames [1920x1080 1252.33 secs (20.87 Mins) @ 15.00 FPS]

As you say you are using screencaps (TechSmith codec), I assumed duplicate sequences would be pretty
identical, looks like (by dropped frame numbers) that this is not the case.
Is there something other than purely desktop involved (do the captures contain windows displaying
streamed video or something else from lossy compressed source). (I'm under impression that TechSmith
is lossless but intended for non complex image capture eg DeskTop with a limited number of colors,
and little change from frame to frame).

Once we get it working OK, then you can use Premiere (I think) or MeGUI to output x264/mp4.

For just now, suggest install correct FrameSel plug, and change config to something like

LODIFFMED  = 1
HIDIFFMED  = 1
LODIFFAL   = 1.0
HIDIFFAL   = 1.0
LODIFFSTD  = 1.0
HIDIFFSTD  = 1.0
LODIFFINR  = 1.0
HIDIFFINR  = 1.0
MAX_LDIFF  = 20.0

and see what happens

Is it possible that you could use VirtualDub to chop out two sets of duplicate frames (about half a dozen of each)
and save them with "Direct Stream Copy" on Video Menu. I dont want to be downloading gigabytes of stuff on my Mobile BroadBand,
ideally no more than about 40-50MB. You can send me PM with link if you prefer.
EDIT: Upload to Mediaifre or SendSpace(no account needed for SendSpace), and maybe 100MB max, I can use broadband
instead.

I'm still playing with this, mainly the KeepUnique version as it seems more useful, also, if you are not using purely desktop
caps then the non keep unique version is probably not the way to go for you either.