Most of us are familiar with DVD menus and the possibility of selecting common language subtitles such as French and Spanish. A third option is often English SDH, English subtitles for the deaf and hard of hearing, which include sound effects of significant off-screen occurrences (such as “[ Doorbell rings ]”), as well as all dialogue.
It is also possible to include English closed caption files (as opposed to subtitle files) on a DVD. Like English SDH, these can be turned on and off, and include sound effects of significant events that occur off-screen, as well as all dialogue. The difference is in some of the technical limitations of caption and subtitle formats having to do with load times of each caption/subtitle and the accommodation of special characters. Please note that Blu-ray players are not capable of passing captioned video to your TV to be decoded. If your ultimate DVD is Blu-ray or will be played on a Blu-ray player, you will need to rely on subtitles.
The advantage of adding a caption file is that if the content is captioned for broadcast TV, the owner can often reuse the same file for the DVD, or a slightly reformatted version of the file. In other words, a caption file in .SCC format can be used for broadcast TV, and can also be encoded to DVD. This can affect the turnaround time of your project, and possibly save the customer money.