Off-line captioning is used to describe the preparation of captioning for prerecorded programs. At time of playback, captions are part of the videocassette. On-line captioning is provided at the time of television program origination. Open -captioning is similar to subtitling. The options for caption placement are great, permitting location anywhere on the screen.
Open captions are usually white letters with a black rim or drop shadow.
Real-time captioning is used for live programs such as presidential speech, sporting event, newscast, or other events that do not allow time to prepare prerecorded captions. Pop-on captions are usually one or two lines of captions that appear onscreen and remain visible for one to several seconds before they disappear. Roll-up captions are usually verbatim and synchronized. The top line of the three disappears as a new bottom line is added, allowing the continuous rolling up of new lines of captions.