How can I black out the first few frames of a video with AVISynth?

I tried this:

black = BlankClip(length=10)
video = AVISource("@source1") 
overlay(video,black)

But now the whole video is black, not only the first 10 fram开发者_StackOverflow社区es... What am I doing wrong?

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The overlay does not automatically end, remember you can also overlay an image instead of a video for instance.

Give a frame for the end of the overlay and then continue the original video from there, like so:

overlay(video, black).trim(0, 10) + video.trim(11, framecount(video))