Moth3r said: FFMPEGSource2 gives me dupe frames on some streams, DGAVDec is very slow, more accurate but still serves the wrong frames sometimes (and is no longer supported by its author).
FFMPEGSource2 is good only for progressive AVC. Was your source interlaced? Putting Assumefps(24000,1001) after FFMS2() in your script can help correct the framerate, but I doubt it helps with dupe frames. (I've never had it give me dupes though.)
EDIT: I assume you demuxed to MKV first. FFMS2() has problems with elementary streams. This is what I do.
LoadPlugin("C:\Program Files (x86)\Haali\MatroskaSplitter\avss.dll")
FFMS2()
DGAVCDec is no longer supported, but its author is still actively working on DGIndexNV, which I highly recommend. If you don't have an NVIDIA card, you might look at DGAVCDecDI if you haven't tried it already.