Odd WMP behavior!

I'm wondering just what the heck happened on this recent resizing project of mine. I was using AVIdemux to resize an AVI. Granted, I was really pushing it, trying to resize a small size resolution to a pretty large one, but still...

When I completed my resizing I opened up the file in Windows Media Player. It played back fine, but the little lever that moves along to the right while the video is playing...Sorry, I don't know the offcial name for it...started on the left and moved to the right in about a minute, which was odd because the file was over a GB in size and it should have at least taken an hour to move from the left to the right, normally.

The reason I'm interested in this, is that, like many people, I like to occasionally grab and drag the slider along close to the to the end to see if the entire file is there.

Incidentally I did get the whole file resized and it played back just fine in WinDVD. So I'm just wondering if this is the sort of behavior one might expect when trying to resize a file to a much larger resolution in AVIdemux.