how to perform edgedetection on each frame found in ImageList?
As others will certainly suggest to you, I suggest that you supply an example of what you are asking about. As far as I can tell there is no function in Mathematica called ImageList. Do you mean a list of images? If so then you Map the function EdgeDetect onto the list of images. I.e. if the list of images is called listOfImages then you would execute
Map[EdgeDetect[#, r, t] &, listOfImages]
with suitable chosen values of r and t.
But perhaps you mean something else. If so please give a more detailed version of your question.
Probably the ImageList in:
listOfImages = Import["ExampleData/clip.mov", "ImageList"]
David’s answer should suffice!