I'm trying to setup my site to store uploaded user content in a 640x360 frame size, which will be presented back for viewing in that frame size and in a smaller frame size.
I'm trying to understand why this site (and others): http://www.encoding.com/what_are_the_best_flash_video_frame_dimensions recommend only the following values for smaller sizes:
384 x 216 128 x 72
when clearly others like:
320 x 180 256 x 144
What is the mathematical reason behind recommending only these frame sizes?