March 2008


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.

Recently I purchased a Zune 30.  The Zune is my first media player, and I have quickly become addicted to it.  I listen to it all day at work.  I plug it into my receiver at home.  It has been loaded with a great deal of music, a number of music videos, a few movies, and every episode of an old TV show I used to watch (MTV’s Sifl and Olly Show– it’s crescent fresh!).  I can hardly wait to get the car kit so I can listen during my morning and afternoon commute.

Frequenting Zune.net under the name “KiloVision”, I have found help for my issues.  In a show of good karma, I try to return the favor by helping those in need.  In that spirit, I decided to start Zunespace.  In the coming time, you will find articles, tutorials, and maybe a few DIY ideas that I hope you will find useful.  Reader input is always welcome.  If you have an idea for something you would like to see here, let me know.