Live Streaming Video Provider with 608/708 Caption Support

There are roughly 466 million deaf or hard of hearing people in the world today. These people often require closed captions to understand what is taking place on TV or video broadcasts. In many places, accommodating these viewers with captions is a legal requirement. This blog post will explain this world and look at a live streaming video provider that supports 608/708 closed captions.

We’ll start by looking at what closed captions are. Then, we’ll discuss why closed captions are important. Next, we’ll look at the two main US legal standards for closed captions—CEA-608 and CEA-708. We’ll close by looking at how to use closed captions with a live streaming video provider, and our support for closed captions when using our streaming solution.

What are closed captions?

Closed captions (CC) are similar to subtitles. They refer to the embedded text in a video stream that allows a viewer to read the text instead of listening to voices in the broadcast. It’s simply the text version of the content you would otherwise listen to.

Typically, closed captions can easily be turned on and off by the viewer. As dialogue or monologue takes place, the captions match the spoken text. Captions will also often include information about music or other important sounds that are included in the broadcast (think booms or gunshots during an action movie, or whistles during a sporting match).

Viewers who are deaf or hard of hearing can follow along by reading with no need to listen to the live broadcast to fully understand what is happening.

Why are captions important?

Live Streaming Video Provider with 608 708 Caption SupportCaptions are important for a few different reasons. First, embedding captions is the right thing to do. It builds rapport with the audience that requires this accommodation and allows you to know you’re helping those who need it.

Second, captions can help grow your audience. Captions aren’t only for those who were born deaf or hard of hearing. As people age, they tend to lose their hearing. Millions of elderly people rely on closed captions. A full 5 percent of the global population is deaf or hard of hearing. Plus, captions are commonly used by people who are trying to learn a new language, and for TVs located in noisy environments (like sports bars). Therefore, to maximize your audience size, you should include closed captions.

Finally, captions are often a legal standard. In the United States (and many other nations), all television broadcasts are required to include closed captions. In addition, online broadcasts that are shown concurrently or near-concurrently (within 12 hours) on TV are required to include closed captions as well. Therefore, it’s important to choose a live streaming video provider that supports closed captions.



  • Captions are the right thing to do
  • Improve accessibility
  • Grow audience size
  • Increase comprehension and clarity
  • Useful for language learners
  • Can increase user engagement and brand recognition
  • Comply with legal standards

In the western world, closed captions follow two main legal standards, CEA-608 and CEA-708. We’ll explain more about these next.

What are CEA-608 and CEA 708?

CEA-608 and CEA-708 both refer to legal standards in the United States, Canada, and Mexico for closed captioning of TV broadcasts. However, both standards are commonly used worldwide.

CEA-608 (sometimes called EIA-608 or “Line 21” captions) is an older standard and was introduced following lawsuits and legislation aimed at making TV programs accessible to people who are deaf or hard of hearing. This standard was cemented in 1990 with the passage of the Television Decoder Circuitry Act.

CEA-708 is the updated standard, which includes a wider array of features and options. CEA-608 is becoming less common as digital TV becomes more prevalent. It’s still widely used, but since 2014 does not meet FCC (Federal Communications Commission) standards for closed captions. CEA-70 is the wave of the future.

Differences between CEA-608 and CEA-708


Live Streaming Video Provider with 608 708 Caption SupportCEA-608/ Line 21 captions

When CEA-608 captions are embedded, they are easy to distinguish by their black box background with uppercase white text. You’ve probably seen this at some point in your life. These captions are commonly used throughout the world.

CEA-608 includes four channels of the caption information. This means, for example, that captions could be broadcast in four languages simultaneously. Often, the first channel is used for English captions and the second is used for Spanish. The original CEA-608 standard supports English, Spanish, French, Portuguese, Italian, German, and Dutch. The standard was also updated in order to support Korean and Japanese — language which require two bytes for each character in the alphabet.


CEA-708 captions

CEA-708 is a newer, updated standard built for the digital television era. The 708 standard supports all the features of CEA-608, plus a new range of features. This includes a wider range of character sets (support for any alphabet in the world), support for many different caption languages simultaneously, and caption positioning options. Positioning is important because FCC regulations state that captions cannot block other important on-screen information.

Viewers can also select between 8 fonts, 3 text sizes, and 64 text/background colors. Drop shadow, background opacity, and text edges can also be customized. This makes it easier for viewers with unique needs to customize the way that they view content.

Note that it’s possible to include CEA-608 captions in a digital TV broadcast, but you can’t use CEA-708 captions with analog transmission.

How to add captions to a live stream

So what about if you’re using a live streaming video provider for online broadcasting? Adding captions to a live stream is a little complex, but it is possible. It’s done at the encoder level. Generally, this happens via a process like this:

  1. A live program is captured via video cameras connected to a production switcher.
  2. The production switcher produces a program feed which is output to an audio embedder, a dedicated piece of hardware.
  3. This audio embedder then provides a feed to a closed caption encoder, sometimes provided by live closed caption service providers, and sometimes maintained in-house.
  4. The live CC vendor converts the audio to text (through an automated, manual, or combination process), then sends this data back to the caption encoder.
  5. The caption encoder receives the captions, then forwards this data to a live video encoder, typically via SDI. Optionally, the caption encoder can delay the video feed to keep the captions closely matched to what’s occurring on-screen. Otherwise, they will be slightly delayed.
  6. The live video encoder captures the SDI input containing the video feed, audio data, and captions, then encodes this into a broadcast-ready feed. This is then sent to your live streaming video provider for ingestion and publishing.

Dacast live streaming video provider support for closed captions

Live Streaming Video Provider with 608 708 Caption SupportMost online video players support subtitles in the WebVTT format. This is the standard for online captions and subtitles. However, if you’re already creating CEA-608/CEA-708 captions, converting these into WebVTT is an additional burdensome step.

Here at Dacast, our video player solution has native support for CEA-608 and CEA-708 closed captions. Our player will automatically detect 608/708 captions that are embedded in h.264 video packages. No configuration is required. They will automatically be added to your videos. In the video player, a clearly marked button allows viewers to easily turn captions on and off, or to select their preferred language.

If you are already delivering your content via digital TV, sharing closed-captioned content with Dacast couldn’t be easier. This is just one of the many ways we are working to provide professional features to our broadcasters.


Hopefully, this article has introduced you to the world of closed captions. Captioning your content can be a legal necessity, but can also be a major boon for your content.

Are you looking for a live streaming video provider with support for CEA-608 (Line 21) and CEA-708 captions? One great option is Dacast. We offer streaming via top tier CDNs, some of the largest in the world. Our live streaming platform also includes a wide range of other professional/OTT features, such as ad-insertion and real-time analytics—all at competitive prices.

Want to give the Dacast live streaming video provider a try? Sign up now for a 30-day free trial, no credit card required!


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