Scaling optimal video frame dimensions
According to the site you referred to:
http://www.encoding.com/what_are_the_best_flash_video_frame_dimensions

The math behind the "Best, Better, and Good" video formats are based on if both Horizontal and Vertical pixels are divided by 16 for best, 8 for better, and 4 for good.

Therefore 256x144 is best, while 384x216 &amp; 128x72 are better, while 320x180 is good.