Google introduced AdSense video units in October 2007. Adsense video units allows you to show YouTube content and ads on your pages. After running it for almost a year and half, Google decided to retire this feature at the end of April.
If you'd still like to display video content from YouTube, you can do so through YouTube.com directly. Visit any specific video page and look for the code in the 'Embed' box, or sign in to your YouTube account to create a playlist. Note that this change won't affect the availability of other video-related ads options - video ads may appear in your AdSense for content ad units if you've opted into image ads, and AdSense for video is still accepting applications from eligible publishers who produce video content.
The option to sign up for video units is no longer available to new publishers. If you're currently displaying video units, Google recommends that you start removing the video unit code from your pages as soon as possible so you can optimize your available ad space in advance. Any earnings you've generated from video units in the past will still be credited to your AdSense account.
Once video units are retired at the end of April, any remaining Leaderboard or Skyscraper video units on your pages will direct users to YouTube.com, while other video unit sizes will automatically be changed to standard embedded YouTube players. These standard video players will display top YouTube videos, but you won't generate earnings from them once this change occurs. If you have less than three ad units on your page, you may prefer to replace your video unit with a regular ad unit.