You may be aware of Text annotations and Captions on youtube videos. To facilitate its userbase, here is a service called CaptionTube which is still under Youtube’s experiment Lab. This web app provides you with a simple caption editor using which you can add captions to any part of the Youtube video and specify when they should appear and for how long.

Caption Editing screen

How it Works?

By selecting how long you want each caption to appear on screen for, and adding beginning and end points for each line of text it’s relatively easy to get a video captioned and ready for the Intertubes. Then, you are required to manually export the captions, and then upload them to your “Captions and Subtitles” page on YouTube.

Source : MakeUseOf