AviSynth Syntax/Grammar

[sambat]

I never bothered much with the structure and syntax of scrips inasmuch as I was content to use samples from posts etc, but trying to make sense of them, I wanted to clear-up a point.
What does the 'clip' refer to in these examples - and why does it sometimes refer to clip2?

AssumeFPS [yv12] [yuy2] [rgb32] [rgb24]

AssumeFPS (clip, int numerator , int denominator, bool "sync_audio")
AssumeFPS (clip, float fps, bool "sync_audio")
AssumeFPS (clip1, clip2, bool "sync_audio") [v2.55]
AssumeFPS (clip, string preset) [v2.57]

[jagabo]

If you don't specify a "clip" (A/V stream) AviSynth will use the "last" A/V stream. For example:

AviSource("filename.avi")
AssumeFPS(60)

implies:

last=AviSource("filename.avi")
last=AssumeFPS(last, 60)

and that is the same as:

AviSource("filename.avi")
AssumeFPS(last, 60)

Pretty much all functions require a "clip" to operate on. Some functions require (or accept) more than one clip:

vid1=AviSource("filename1.avi")
vid2=AviSource("filename2.avi")
last=Merge(vid1, vid2)

[sambat]

Got it:thank you!