ATSC 3.0 Expands Closed-Caption Offerings

ALEXANDRIA, VA.—As the industry pushes forward with ATSC 3.0, the new standard will revolutionize more than just the way content is delivered, it will also expand the capabilities of closed captioning and audio description. TV Technology recently sat down with Chris Homer, vice president of operations and engineering for PBS to discuss the potential improvements to accessibility services under the new proposed standard. Homer also chairs the Advanced Television Systems Committee’s S34-5 ad hoc group on accessibility in the ATSC 3.0 Specialist Group on Applications and Presentation.

Chris HomerTV TECHNOLOGY:What will be the main differences between current closed captioning services under ATSC 1.0 and 3.0?

CHRIS HOMER: Many of the proposed closed caption systems are based on SMPTE-TT (Timed-Text), which supports worldwide languages and symbols and images. And it’s based on Internet Protocol, rather than transport stream, meaning that broadcasters can take advantage of existing standards and protocols used today for Internet delivery of caption services. In addition to offering the same caption-quality standards of ATSC 1.0, captioning in ATSC 3.0 will enable new features thanks to the hybrid broadcast/broadband approach. In this mode, caption files can be sent via broadcast and broadband so the viewer can have more choices. This may be in the form of closed captions or subtitles for alternate languages, for instance.

TVT:How have the evolving FCC rules on closed captioning affected planning for ATSC 3.0 closed captioning proposals?

HOMER: The evolving rules have accomplished a couple of things; there’s been an increase in awareness and efforts to ensure captions are accurate, complete, in sync and placed at the appropriate position relative to the raster image. The rules have also been expanded to Internet delivery, so now broadcasters and OTT providers share a common process. This has been helpful in evaluating caption delivery proposals for ATSC 3.0.

TVT:FCC rules on program access cover more than just closed captioning; they also include video description. Can you elaborate on what ATSC 3.0 has in store for video description?

HOMER: While the current work of the group that I chair is focused on closed captions, the ATSC also is addressing Descriptive Video for ATSC 3.0. We’re very excited about what is possible with Descriptive Video. That’s because the audio system for ATSC 3.0 will have new features that allow alternate audio to be seen as objects so the Descriptive Video or Alternate Language audience can experience the full audio immersion experience.

TVT:How many different types of captions do you expect ATSC 3.0 to support?

HOMER: ATSC 3.0 will support both closed captions and subtitles, and multiple choices could be available using the broadcast/broadband approach. A typical broadcast might offer both English and Spanish captions for the over-the- air broadcast and at the same time other languages might be sent as subtitles over broadband. That said, if a broadcaster would like to include more languages in the OTA broadcast, they can configure their emission to do that, too.

TVT:How many secondary audio programs/services? (This would include a video description service.)

HOMER: A typical ATSC 3.0 broadcast will have capability for multiple audio streams such as English, Spanish, Descriptive Video and others sent via broadcast—with even more languages like French or German being sent via broadband. Since each service is simply an object within the full mix, there’s minimal cost of capacity required.

TVT:How many of these services do you expect could be available on the low-bandwidth “robust” video feed?

HOMER: In ATSC 3.0 the broadcaster will have choices in how to use their bandwidth. The standard allows for multiple “physical layer pipes” that can each be configured for different business cases such as less robust, high-capacity PLPs targeted to fixed receivers and more robust PLPs to support mobile devices and everything in between.

TVT:Will there be different rules/requirements for broadcast and streaming?

HOMER: This is a question that will ultimately need to be answered by the FCC, but I believe those regulations will be reviewed at the appropriate time as ATSC 3.0 progresses.

TVT:What will ATSC 3.0 provide for closed captioning capabilities for emergency alerts?

HOMER: Emergency alert captions are already addressed through the current system and are not expected to change in the near-term. With its advanced emergency alerting capability, ATSC 3.0 will make it possible to add enhanced rich-media alerting content provided by the broadcaster such as banner text, audio, weather maps, news updates to provide specific information for the public, including people with disabilities.

TVT:The current DTV standard supports many captioning options, but very few of these are used. Is there any reason to believe that this will be any different with the captioning options available with ATSC 3.0?

HOMER: The enhanced features of CEA-708 have not been fully adopted by the broadcast and MVPD industries, and instead the older and simpler CEA-608 feature set continues to be used primarily in ATSC 1.0, kind of a holdover from the NTSC days.

Looking ahead, ATSC 3.0 will present some exciting new captioning opportunities, but as we move forward as an industry with the standard, we’ll have to be careful not to disrupt the work upstream. For example, it may be possible in the future for a viewer to move a caption display off the image for convenience, but if the caption provider or program producer intended the placement of captions on the screen to show who in the image is speaking, then this intent is lost.

TVT:What is the timeline for adoption?

HOMER: Everyone is working diligently on getting the basics in place this year for caption delivery in the ATSC 3.0 Candidate Standard. But our work doesn’t stop there. The group I’m working with will be looking at all aspects of accessibility to ensure we have a platform for the future that can allow more audience engagement with a process that works for the broadcast and consumer electronics industries.

Tom Butts

Tom has covered the broadcast technology market for the past 25 years, including three years handling member communications for the National Association of Broadcasters followed by a year as editor of Video Technology News and DTV Business executive newsletters for Phillips Publishing. In 1999 he launched for internet B2B portal Verticalnet. He is also a charter member of the CTA's Academy of Digital TV Pioneers. Since 2001, he has been editor-in-chief of TV Tech (, the leading source of news and information on broadcast and related media technology and is a frequent contributor and moderator to the brand’s Tech Leadership events.