Think back to math class.  Remember when your teacher said, “Pay attention!  This might save your life some day.”  Well, today is that day.  OK, so this might not save your life… unless your life depends on transcoding videos correctly.  Sometimes it is necessary to resize a video to make it fit the Zune’s display.  To do this one needs to understand aspect ratio.

A ratio is simply a comparison.  Like “16 to 9″or “4 to 3”.  Ratios can be represented with a colon between numbers (16:9, 4:3) or as fractions (16/9, 4/3).

The aspect ratio of a video is a comparison of the video’s width to it’s height.  An aspect ratio is always expressed as a ratio of the longer side to the shorter side.

Normal screen video has an aspect ratio of 4:3.  Regardless of the video’s actual dimensions, for every 4 pixels of width, the video will have 3 pixels of height.  Examples of 4:3 include 320×240 and 640×480.  If you pull out a calculator, you will find that 640/480 = 320/240 = 4/3.

Wide screen video has an aspect ratio of 16:9.  For every 16 pixels of width there will be 9 pixels of height.  Examples include 320×180 and 720×405.  Again, with the calculator, 720/405 = 320/180 = 16/9.  (Note: there are actually several ratios that are “widescreen”– 15:9, 16:10, etc.  16:9 is the aspect ratio for HDTV.)

Now that we understand the basics, let’s apply them.  Let’s assume that you have downloaded a video in AVI format and found it to be 450×300.  You decide to resize the video to fit the Zune’s screen while converting it from AVI.  To maximize screen usage, you know that the new width will be 320 (the width of the Zune’s screen).  To calculate the new height, we need to compare the width/height ratio of the source video to the ratio of our new video:

Aspect Ratio Example

450/300 is the ratio of the source video’s width and height.  320/H is the ratio of our transcoded video.  320 is the new width and H will be the new height.  Following the steps, we get 213.33.  Always round decimals to the nearest power of 2.  Doing this makes the new height of the video 214.  You can now start your favorite video transcoding software and set the output video’s resolution to be 320×214.

Video gurus may find this information very basic.  If you have something to add, please comment!  For those of you that are new to converting videos, I hope this makes transcoding your next video a little easier.