Use of online video has grown faster than the use of accessibility in online video. Though bandwidth costs for video files can still be high compared to ordinary text-and-graphics Web pages, it is nonetheless easy to digitize video and post it online. It's easier to broadcast your video to the world via the Internet than it is to get the same video on television. Online multimedia are a useful and valid new medium of communication - for most people.
There are two methods for adding captions in QuickTime. There are advantages and disadvantages to each approach. The first allows you to maintain a single file, making the captioned video easier to distribute. The second approach allows you to easily deliver a captioned and non-captioned version of your movie, but requires an understanding of SMIL (it's not too hard).
RealPlayer uses SMIL to combine media content with a RealText (.rt) file. The .rt file contains the captions themselves and information about how and when they should appear. The SMIL file is really just a pointer file. It contains information about where and how your captions and media content should display.
Windows Media Player adds captions using Microsoft's Synchronized Accessible Media Interchange (SAMI). SAMI, like SMIL, which is used by Quicktime and RealPlayer, is an XML-based text language. A SAMI file contains the captions and definitions for how and when the captions should display.
When delivering multimedia content for the three major media players (Windows Media Player, Quicktime and RealMedia Player), the developer must choose whether to have the viewer access the content through a player embedded in a Web page or through a standalone player. Both methods have their advantages. Embedding the player in a Web page allows the user to access the content without another application opening. The standalone players usually have more control options.