This format is used primarily by television broadcasters. The file itself is encoded into line 21 of the video (which is generally not visible) by using an encoder, a piece of hardware that does only this. On the viewer’s end, their television decodes the information encoded on line 21 and displays it as closed captions.
The information that can by contained in a .SCC file is limited to time, content, and position on screen. Most sets can interpret text color information as well. Font is determined by the television set. If the file is encoded with the wrong font on the captioner’s end, characters may disappear or be displayed incorrectly. This is especially common with apostrophes.
.SCC files are also used by other applications as well. Many DVD authoring programs can import .SCC files into their workflow.