[Athen] HDTV and Captions

Sean J Keegan skeegan at stanford.edu
Mon Dec 8 11:20:32 PST 2008

> The quick question is do the HDTVs have captioning?

HDTVs generally have caption decoders, but that is just a small part of the larger picture.

You can view closed captions on a HD system, BUT it depends on a number of factors that includes how the TV is connected to the "source", the devices between the "source" and the TV, the cables being used, etc. I have been trying to figure this out for some time and it can get complicated.

Most new HDTVs have a caption decoder, but if you are connecting to the TV with a HDMI cable then I do not believe the TV would be doing the decoding (the HDMI spec does not include support for caption data). The decoding would need to take place either in the DVD player or set-top box and then overlayed onto the video before being sent to the TV. Wikipedia has a quick overview of some of the incompatibility issues here:

If the TV station is transmitting caption data as part of the HD data stream and you are using a built-in tuner (e.g., QAM tuner), then the TV should be able to display the caption information (just enable the caption option). The TV itself is doing the decoding of the video data stream and overlaying the display of the captions. If you are using a set-top box, then my suggestion would be to enable captions on the set-top box as this will decode the video data stream and then overlay the display of captions before transmitting to the TV.

Take care,

Sean Keegan
Associate Director, Assistive Technology
Office of Accessible Education
Stanford University

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