At tourism marketing workshops I have been telling everyone to start recording video for the Web in HD format for two years. Checking my feed from Lifehacker and noticed Gina Trapani reporting that YouTube has adjusted the the video clip player’s size from a 4:3 aspect ratio to 16:9 (HD TV format). As a result, many clips that were recorded in standard definition 4:3 ratio will now have black bars on either side to fill in the new space.
If you listened to the advice I was giving you back then you would have seen black bars at the top and bottom of your videos. Now however, you’ll notice your HD videos in 16:9 format now fit the Youtube player perfectly.
Instead, you’ll notice the black bars (pillar boxing – in video lingo) on any Youtube video that was filmed in standard definition.

How to Get rid of the black bars when you post to Youtube?
To get rid of the black bars in your videos, be sure to record and edit all future videos in HD or 16:9 ratio. That way, your video will play completely filling the viewer. Voila, no more black bars!
Unfortunately, there is no way to get rid of the black bars on existing standard definition videos

{ 2 comments… read them below or add one }
if i decrypt a dvd that has a display aspect ratio of 16:9 and 2.35:1 (720×480) so there is a black bar on the top and bottom…if i re-encode and simply just change one thing, the display aspect ratio from 2.35:1 to 1.78:1 without cropping …would it get rid of the black bars and keep it 720×480
normally people crop the black bars first so it would be something like 720×362 and then it gets resized to usually 624×352 …but couldnt i jus change the display aspect ratio and thatll do it?
you can get rid of the black bars by using Quicktime Pro.
This explains how: http://www.youtube.com/watch?v=HKS9wgmZ9Mw