Possible Purposes Include:
Access for viewers who are deaf or hard of hearing.
Multi-languages.
On-screen text converts the spoken word and other audio contained in videos, TV programs, web-based multi-media and movies to text.
There are different types of on-screen text. The following three are commonly used.
Subtitling: Subtitles are used to communicate the spoken word in a different language. They can also be used for audiences who are hard of hearing.
Closed Captioning: Closed captioning is the addition of text inserted into the video portion of the signal using an encoder and made visible through the use of a decoder. Television sets with screens larger than 14 inches since 1995 contain a caption decoder chip.
Open Captioning: Open captioning is the decoding of words visible on-screen without the use of a decoder or any assistive device.