The following line works in standard avisynth but not in avs+ x64.
Code:
black = BlankClip(last, width=64, height=32, Color_yuv=color_black)
and probably the next (forgot to test, and i'm under standard avisynth without avs+ access while writing these lines).
Code:
white = BlankClip(last, width=64, height=32, Color_yuv=color_white)