Multiplies clip size and changes aspect ratio to 4:3

/*
 * Example AviSynth script for PrismJS demonstration.
 * By Zinfidel
 */

SetFilterMTMode("DEFAULT_MT_MODE", MT_MULTI_INSTANCE)
AddAutoloadDir("MAINSCRIPTDIR/programs/plugins")

# Multiplies clip size and changes aspect ratio to 4:3
function CorrectAspectRatio(clip c, int scaleFactor, bool "useNearestNeighbor") {
    useNearestNeighbor = default(useNearestNeighbor, false)
    stretchFactor = (c.Height * (4 / 3)) / c.Width

    return useNearestNeighbor \
        ? c.PointResize(c.Width * scaleFactor * stretchFactor, c.Height * scaleFactor) \
        : c.Lanczos4Resize(c.Width * scaleFactor * stretchFactor, c.Height * scaleFactor)
}

AviSource("myclip.avi")
last.CorrectAspectRatio(3, yes)

Prefetch(4)