what causes this flickering after encoding?

[zanzar]

v = LWLibavVideoSource("d:\4.mp4", fpsnum=30000, fpsden=1001)
a = LWLibavAudioSource("d:\4.mp4")
AudioDub(a,v)
ColorMatrix(mode="Rec.601->Rec.709
FastLineDarkenMod()
aWarpSharp(depth=3)
nnedi3_rpow2(2, cshift="Spline36Resize", fwidth=1280, fheight=720)
aWarpSharp(depth=10)
Sharpen(0.4)

here how it looks i flikers i variant of colors also happened to a certain videos not all although they are all mp4

http://imgur.com/a/OMgmx

[sneaker]

Is the source video bitdepth > 8 bit? Try:
v = LWLibavVideoSource("d:\4.mp4", fpsnum=30000, fpsden=1001, format="YUV420P8")