Pixel Aspect Ratio - Factor used to compute an approximation of the aspect
ratio of the pixel in the original image. If the value of the field is not
0, this approximation of the aspect ratio is computed based on the formula:
Aspect Ratio = (Pixel Aspect Ratio + 15) / 64 The Pixel Aspect Ratio is defined
to be the quotient of the pixel’s width over its height. The value range
in this field allows specification of the widest pixel of 4:1 to the tallest
pixel of 1:4 in increments of 1/64th. Values : 0 - No aspect ratio information
is given. 1..255 - Value used in the computation.