CEA-608 vs. CEA-708: How to Add Closed Captions to a Live Stream [2021 Update]

CEA-608 vs. CEA-708_ How to Add Closed Captions to a Live Stream Image

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 in videos. 

In many places, accommodating these viewers with captions is a legal requirement. However, many brands are becoming more inclusive and courteous by making their content accessible to a larger audience.

In this post, we will discuss everything you need to know about CEA-608 and CEA-708 closed captions. We’ll start by looking at what closed captions are. Then, we’ll discuss why closed captions are important.

From there, 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 live streaming and Dacast’s support for closed captions when using our streaming platform.

Table of Contents:

  • What are Closed Captions?
  • Why are Captions Important?
  • What are CEA-608 and CEA 708?
  • CEA-608 vs. CEA-708
  • How to Add Captions to a Live Stream
  • How to Add Closed Captions on VOD Content on Dacast
  • Streaming Video Provider Support for Closed Captions
  • Conclusion

What are Closed Captions?

What are Closed Captions
Closed captions are an important tool for accessibility in online streaming.

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, such as 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.

Open Captions vs. Closed Captions

The difference between open captions and open captions is the viewers’ ability to turn them off at their command. As we mentioned, closed captions can be turned on or off with the click of a button.

Open captions, on the other hand, cannot be turned off. They simply stay on the screen.

Why are Captions Important?

Captions 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.

Captions can help grow your audience. Around 15% of American adults are hard of hearing or deaf. By making your content accessible, you can tap into this audience.

However, 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 to access information via video content.

Additionally, captions are commonly used by people who are trying to learn a new language. TVs located in noisy environments, like sports bars, also use. Therefore, to maximize your audience size, you should include closed captions.

Captions are also often a legal standard in many nations. In the United States, in particular, 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.

That said, it’s important to choose a live video provider with a streaming setup that supports closed captions so that you can comply with your local guidelines and restrictions.

What are CEA-608 and CEA-708?

closed caption encoder software
CEA-608 and CEA-708 are two major capturing standards.

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-708 is the wave of the future since it meets FCC (Federal Communications Commission) standards for closed captions that were introduced in 2014 and CEA-608 does not.

CEA-608 vs. CEA-708

Let’s take a closer look at what each of these captioning standards means for broadcasters.

CEA-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 since these captions are commonly used throughout the world.

CEA-608 includes four channels of 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.

Another notable aspect of CEA-608 captions is that the fonts, positioning, and text sizes are fixed, which means that broadcasters can’t customize them to their liking.

The original CEA-608 standard supports English, Spanish, French, Portuguese, Italian, German, and Dutch. The standard was also updated to support Korean and Japanese which are languages that require two bytes for each character in the alphabet.

CEA-608 is becoming less common as digital TV becomes more prevalent since it doesn’t adhere to the most recent regulations in the United States.

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 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.

Since CEA-708 supports any characters, it can be used for captioning in just about any language.

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 

how to embed closed captioning
Incorporating automatic captioning in your live streams takes a bit of preparation.

Adding captions to a live stream is a little complex, but it is definitely possible. Generally, it’s done at the encoder level.

The process looks something like this:

  1. A live stream is captured via video cameras connected to a production software/encoder
  2. The encoder produces a program feed which is output to an audio embedder, which is a dedicated tool
  3. This audio embedder then provides a feed to a closed caption encoder
  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.

With that said, it is important that you choose a reliable encoder or dedicated closed captioning software to work alongside your video streaming platform

Closed Captioning Software Options 

Here are a few of the top closed captioning software options:

As you research and compare other options, be sure to focus on platforms that offer support for live captioning specifically.

How to Add Closed Captions on VOD Content on Dacast

Dacast allows broadcasters to add subtitles to on-demand video files without the integration of third-party software or encoder. 

To add subtitles to your VOD content, click on the video file you wish to modify. Go to the “General” tab, and scroll down to “Subtitles”:

How to Add Captions to a Live StreamThis displays all current subtitles on the video file and gives you the ability to add subtitle files. To do this, click the “Create Subtitles” button. You will need to find WebVTT (aka VTT files) or SRT files to upload.

If you don’t already have them, these files are easy to create in a simple text editor.

Here are two examples for WebVTT and SRT files.

WebVTT Subtitle File Example

VTT files are very easy to create using Notepad or any other plain text editor program. Below is an example of what a cue looks like for a VTT file. The first number is when the subtitle is supposed to appear. The second timestamp is when the subtitle is supposed to disappear:

00:00:06,000 –> 00:00:11,000

I hear there is a motion in the wind.

00:00:12,500 –> 00:00:16,500

Yes, I have heard it as well. Like a soft breeze of change.

00:00:18,500 –> 00:00:24,000

Isn’t this example a little too poetic for subtitle creation?

00:00:25,500 –> 00:00:34,000

Very, but it still gets the point across.

If you want to use languages other than English, the VTT files must be saved using UTF8 encoding to have characters displayed properly.

SRT Subtitle Example

Here is an SRT example. It functions similarly to the timestamp method of the VTT files.

Entries must be formatted like this:

  • Subtitle Number: 10
  • Start Time –> End Time
  • Subtitle text
  • Blank line

This is what it will look like in action:


00:15:25.000 –> 00:15:29.000

This is a test subtitle A


00:15:29.000 –> 00:15:32.000

This is a test subtitle B

The example above would make the first subtitle (test subtitle A) appear at 15 minutes and 25 seconds in video playback. It would disappear at exactly 15 minutes and 29 seconds.

The second subtitle (test subtitle B) would appear at 15 minutes and 29 seconds, and then it would disappear at 15 minutes and 32 seconds exactly.

Streaming Video Provider Support for Closed Captions

Most 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 HTML5 video player 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 boost for the quality of your content and your viewers’ experience.

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.

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Max Wilbert

Max Wilbert is a passionate writer, live streaming practitioner, and has strong expertise in the video streaming industry.