I doubt that the cpu in the 4G ipod is powerful enough to play video well.  I know for a fact that apple started using a much faster cpu in the 5G so that it could decode mpeg4 and h.264.

I would imagine that even if you got it to play video that it would be jerky and not very enjoyable. 
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Mac mini C2D 1.83GHz - 2GB RAM - 200GB 7200rpm HD
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