click here to skip directly to page content
Media Access Group  Versión en español
About Us Services and Products Research and Development Resources Get Involved

A variety of services that help to make television, movies and more accessible for all.


Captioning FAQ

Caption Transmission and Distribution: Avoiding the Most Common Problems
The caption signal (which is recorded on line 21 of the vertical blanking interval) is normally quite strong, but it can become garbled, damaged, or completely erased.

Caption Transmission Problems
  • Poor signal reception by consumer equipment
  • Damage to the TV signal from being routed through devices which alter, block, or wipe out line 21. This can occur at the broadcast source or at the local station or cable operator.

Caption Distribution Problems
  • An uncaptioned master tape is used for duplication of videocassettes.
  • Hollywood films may have been captioned for special purposes, but the display rights did not include broadcast television.
  • A program is sold into syndication or home video distribution, and the new distributor is unaware that the program has been captioned. If the program is reformatted or edited, the caption data must be reformatted at a minimal, but necessary, cost.
  • A station is time-compressing video to allow for more commercial time. Time compression does not strip captions entirely, but it removes enough of the caption data from the program that words will be missing, badly garbled, and unreadable.

Avoiding the Most Common Problems
Most caption problems can be avoided by broadcasters or duplicators checking to see that all equipment in the video path is set to pass line 21, monitoring the captions of the off-air signal, and/or checking to see that the closed-captioned master tape is being used for broadcast or video duplication. Note that as of January 1, 1998, program distributors are required by the FCC to pass captioned programming along to viewers with the captions intact.


















Caption Services Description Services NCAM