Monday, April 07, 2008

From the mailbag: Closed captioning with DTV

From: Ruth in Akron

Q: I often use the closed captioning on my TV set to help me since I don't hear so well anymore...Will it still be available on the new digital TVs?

A: An excellent question... The answer is yes!

Analog TV has only one format for closed captions in which the captions are encoded invisibly in the analog TV signal.

However, Digital TV can support two formats. The second format is newer and offers more choices of font, color, and size, which can result in better visibility and ease of use. Digital TV carries captions of either format as data along with the digital audio and video content, but unlike analog TV, the captions are not embedded in the video signal.

Basically, it is up to the originator of the programming to provide the captions for any given program and to select the format. When the captions are decoded and displayed, the resulting text and symbols appear on the screen. The caption decoding function, by U.S. government mandate, is included in all digital TVs that have a screen size 13 inches or larger. It is also included in all separate, stand-alone digital TV tuners (e.g., set top boxes or "STBs").

In either case, the digital TV tuner reads the closed caption data, interprets it, and writes it into the video so it becomes visible when the video is displayed on a screen. (More specifically, the captions are written on top of the video images.)

You can email your questions to me:

No comments: