Encoders and Decoders for Closed Captioning

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Closed captioning encoders are used to encode closed captions into the television signal. Before digital television arrived, the type of closed captioning used was known as CEA-608 closed captioning, a standard from the Consumer Electronics Association. CEA-608 captions are encoded onto line 21 of the vertical blanking interval of the television signal. Today, CEA-608 captions are often referred to in the industry as "legacy" captions.

When digital television began, the new closed captioning standard was known as CEA-708. CEA-708 captions allow the viewer to have more control over the closed captions. A viewer of CEA-708 captions can control the size of the captions, the type of font used, and the text and background colors.

Several companies manufacture the hardware needed by broadcasters, post production facilities, and closed captioning services, for encoding and transmitting closed captions. Encoders insert the closed captioning data, which is not visible until a device (such as a television with a built-in closed captioning chip) decodes it. Some products are dual encoders/decoders. An encoder with a decoding function can display captions from an incoming video signal.

Manufacturers of Encoders/Decoders

Examples of companies that manufacture closed captioning encoding/decoding hardware:

  • Link Electronics - Link Electronics has been in business since 1989. The company added closed captioning hardware to its product lineup in 1993. Currently Link Electronics carries about a dozen models of closed captioning encoders and decoders.
  • EEG Enterprises Inc. - EEG produces several products for closed captioning, not just encoders and decoders. Some decoders are also capable of monitoring the closed captioning. A realtime (live) closed captioning systems offered by EEG enables the use of multiple closed caption encoders on one phone line. EEG sells multiple categories of closed captioning encoding and decoding products, including HDTV (high definition digital television) captioning, NTSC (Line 21) captioning, and caption data bridges that can move the closed captioning out of the way of an emergency text crawl.
  • Evertz - Evertz sells closed captioning software as well as encoders. The company manufactures a handful of encoders/decoders, including for digital television.
  • Wohler - Wohler sells a handful of closed captioning encoding, decoding, and bridge products. The company posts the prices for some of its products; a dual channel CEA-608/CEA-708 decoder and monitor was listed for almost $5,000 in 2011 dollars.

Broadcasters that do not use tape for non-live programming, can use tapeless closed captioning services. With tapeless closed captioning services, a broadcaster submits the video via FTP (instead of sending a tape) to the closed captioning service. The closed captioning service adds the captions, and returns a video file with the closed captioning data. Broadcasters then import the video into their own systems. Using a tapeless closed captioning workflow eliminates the need for the use of the encoding hardware by broadcasters. Another term for tapeless closed captioning is "e-captioning."

Early History of Decoders

Originally the closed caption decoder was a large device that the viewer attached to the television. In 1990 the Television Decoder Circuitry Act required all televisions 13 inches or larger, to have built-in closed caption decoding circuitry starting in 1993. The stand-alone closed captioning decoder shrank, and became small and portable. Today, all that remains is the V-gis parental monitoring closed captioning decoder that utilizes V-chip technology to filter programs. However, an internet search could not locate the manufacturer.

It appears that the market for closed captioning encoding and decoding hardware will remain a limited, specialized market. One reason for this is the growth of tapeless captioning workflows. As fewer broadcasters need encoders, the primary users of encoders/decoders will probably be the closed captioning services and post-production houses.

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