READ more YouTube Adds a Built-In Video Editor
“Until now, when you uploaded to YouTube, your video was hosted and shared, but couldn’t really be changed. If you wanted to trim off the end, swap out the soundtrack, or add an effect, you had to edit your video using a separate program and upload again.
Starting today, you can edit your uploaded videos right on YouTube and maintain the same video IDs. This means you keep your view count and comments, and all existing links to your video will continue to work. No re-uploading necessary!”
READ more on the YouTube Blog