Digital TV Captioning Challenges Viewers

By Craig Johnston, TVTechnology.com

August 2009

Editor: We've probably all heard stories about difficulties getting caption to work on digital TVs. Here's a great article on the topic from the folks at TVTechnology.com, as distributed by NVRC.

For the full article with illustration: http://www.tvtechnology.com/article/85298

~~~~~~~~~~~~~~~~~

DTV closed captioning has a number of challenges to overcome, as complaints from viewers about missing captions, garbled captions and improperly formatted captions have been streaming in. And while problems with DTV captioning will be detailed in this article, an over-arching statement should be made up front: the sky is not really falling.

The issue of DTV closed captions is being addressed; manufacturers are cooperating; and tools are being created.

Closed captioning was developed in the 1970s to provide a text display of spoken audio in television programming for deaf viewers that could be optionally displayed. The analog system of closed captioning-CEA-608-usually provided simple white capital letters over a black background, a character set that included upper and lower case Roman letters and a limited number of accented characters for French, Spanish, Portuguese, Italian and German, along with a simple display of up to 32 characters per line.

In the analog 608 system, the captioning text and control information was hidden in line 21 of the NTSC vertical interval, where it could be retrieved and displayed by a closed caption decoder that was either built into the TV or other device, or sold as a standalone unit. The line 21 encoding was relatively bulletproof, able to survive off-air, cable and satellite transmission, as well as professional and consumer tape recording and playback.

DTV CAPTIONING OFFERS ENHANCED FEATURE SET

Development of DTV provided the opportunity to significantly improve closed captioning, and the CEA-708 DTV captioning standard, which was adopted in the late 1990s, provides an almost unlimited Unicode character set that expands on the previous closed captioning character set. This enhancement now provides captioners with the capability to display characters from previously unsupported languages such as Chinese and Japanese.

Those authoring 708 captions have the option of placing multiple windows for text on the screen, and the system provides a myriad of options for the viewer to customize caption display. These include fonts, font sizes and background colors, along with positioning on home video display devices.

The FCC requires that a DTV transmission contain both CEA-708 and 608 captions to be encoded into the MPEG stream. The 608 captions are intended for the DTV decoding boxes.

NEW CAPTIONING ALSO DRAWS COMPLAINTS

There have been no shortage of complaints from viewers about the new DTV caption, according to Marc Okrand, who is the National Captioning Institute (NCI) director of Live Captioning. However, few of these have come from those viewing off-air DTV signals. Rather, they come from cable and satellite TV viewers, who say captions are missing or are garbled.

"We've gotten complaints that say channels 1 to 100 are fine, but on channels above that letters keep dropping out," said Okrand.

One big change for caption viewers to adjust to is in how they control caption display. With the DTV system, the captions have to be decoded where the MPEG stream is decoded, and with the exception of off-air signal reception, that means at the cable or satellite set-top box. Viewers who are used to hitting a button on their TV remote to display closed captioning will not find captioning there, so a major education effort is indicated.

"Cable boxes are not captioning friendly," said Okrand. "You have to go into the cable box menu in order to turn the captions on and off, not just hit a button."

He said that although NCI has heard few complaints about off-air broadcast caption decoding at this point, that may be because viewers have only just begun watching DTV.

DTV captioning issues have mostly remained under the radar, as so much effort and attention went into the June transition to DTV itself. However, on May 18 an FCC technical working group held its first meeting to deal with DTV closed captioning and video description issues. [DTV video description issues are beyond the scope of this article, and will be discussed in a later issue of TV Technology.]

"What we tried to do with the working group is bring together all of the technical experts, both on the equipment manufacturers side, broadcasters' side, cable and satellite, experts in from the user community," said Julius Knapp, FCC Office of Engineering and Technology (OET) chief, and co-chair of the working group. "And in a collaborative way, better understand what the problems are, what their costs are, and how we can fix them."

Larry Goldberg, Director of Media Access at WGBH, home of The Caption Center, and himself a member of the FCC's working group, calls the meetings a good route to solution of the DTV caption problems.

"The FCC has all of the players in the same room...there can be no ducking," Goldberg said.

NEED FOR EASY ACCESS

One of the first moves that Goldberg predicted is for cable and satellite TV companies to put caption display in the first level of their menus.

With tens of millions of set top boxes recently deployed to bring DTV to viewers, that may seem to be a costly step.

"Set-top boxes can download new firmware," said Steve Blumenschein, president of XOrbit, developers of the CaptionSmart MPEG file captioning service, which delivers its product via secure online.

Right now, almost all of the live text seen on TV screens displaying 708 captioning is being upconverted from 608 captioning. Alan Hightower, a Wegener software developer, said that some of this comes down to legacy equipment and costs.

"I don't think broadcasters want to bear the cost of authoring separate close captioning content for both standards," he said.

Until recently broadcasters have been required to provide 608 captioning for their analog channel, so they authored in 608 and upconverted to 708.

However, XOrbit's Blumenschein identified another reason for not starting with 708 and downconverting to 608, which, for example, would require a computer program to figure out how to handle text in multiple windows.

"If I do 708 and try to downconvert to 608, it's not going to work very well, because I'm going to lose a lot...I don't know how to deal with the lost information," Blumenschein said. "I know I can drop it, but I don't know if it was important and what I should do to imitate it."

IT'S TIME TO MOVE ON

One company that does offer 708 authoring software is Computer Prompting & Captioning Co. (CPC). Jason Livingston, CPC technical support specialist makes a strong case for taking advantage of the capabilities of the 708 standard rather than upconverting from 608.

"That's kind of like saying I've got a VHS tape and I'm going to upconvert it to HD and I'm now broadcasting HD," said Livingston. "Yes, you're broadcasting HD but you're not getting any of the advantages of HD by doing that."

CPC also gave TV Technology a heads-up on its new MacCaption Monitor and Caption Maker Monitor (Windows) products, which takes caption monitoring functionality from its authoring products and sells it as standalone caption monitoring capable of monitoring caption encoded in the MPEG-2 stream.

Monitors can be placed at various points in the workflow and signal path to determine where a captioning problem originated. Volicon also provides closed caption monitoring as part of its Observer broadcast monitoring system.

"As part of its monitoring, it captures audio and video and associated metadata that is related to this broadcast," said Volicon CTO Gary Leamer. "The broadcaster is able to provide proof of broadcast to the FCC, and that includes closed captioning."

AUTOMATIC ERROR DETECTION AND CORRECTION

Two builders of closed caption encoders have used their experience with captioning and what can go wrong with it to build devices that do automatic error correction.

"We actually never intended to be in the caption correction business," said EEG president Phil McLaughlin, "But we looked at the problems and said 'hey, we can fix this.'"

EEG's CB512: HD Caption Legalizer/ Relocating Bridge can compare the 708 caption text to the 608 text to help fill in garbled sections, and can reformat captions to fit supported constructs for decoding and display.

According to Evertz Product Manager Tony Zare, his company's HD9084 HD DTV closed caption encoder not only encodes new captions on productions, but can analyze captions on existing captioned material.

"You can run the master through one of these devices [and] the machine will analyze the closed captioning content and fill in the blanks, almost like an automatic scrubber of corrupt captions," Zare said.

Evertz also builds its closed caption technology into other devices like video crossconverters and multiviewers.

A couple of other DTV caption products that could make life easier include a caption translator that's soon to appear from Wohler. "We've got a world exclusive for you," said Andrew Hutton, FPGA hardware designer at Wohler. "We'll be launching a converter from 608/708 to [Europe and Australian standard] OP47 captions, and vice versa."

And Softel-USA has its Swift TX, which allows the captioning text and instructions to exist as a file on a server until it's time to play them back.

"The benefit is you've got the caption data available for transcode to specific targets, whether it's SD or HD for broadcast, transport streams for VOD systems, or Web delivery, you can then use that caption data," said Softel president Ed Humphrey.

"We knew from experience that every broadcaster has a different workflow, and therefore we need to be able to plug into those workflows where the customer wants."

So there's plenty of attention now focused on DTV captioning and its delivery to the viewer, and plenty of tools to solve technical problems and streamline the process.

But it seems that just as the captioning people are beginning to sort things out in the new digital world, there appears to be a new wrinkle looming ahead which is bound to cause some concern. Congressman Edward Markey (D-MA) has introduced the 21st Century Communications and Video Accessibility Act of 2009. It's a good bet the industry would rather fix closed captioning by themselves.

~~~~~

NVRC NOTE: The final paragraph in this article is confusing. The 21st Centrury Communications and Video Accessibility Act of 2009 does not have anything to do with TV broadcast captioning over the air or by cable or satellite; it addresses captioning on the Internet.

~~~~~