Tips on Inserting Live Captioning into Internet Video

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We used to think that live captioning of an Internet video broadcast was rocket science. Television stations used special equipment to do something called “line 21 insertion”. Thankfully, injecting open captioning into live internet video broadcasting doesn’t require anything more than a good Internet connection at the live venue and a stenographer with access to the web. Here is how it works: First, setup all the audio and video gear at a venue like you would normally do for a broadcast and test the Internet connection. After establishing a good Internet connection you take an output from your main audio mixer and plug it into a laptop running Skype.


\Your captioner can be located anywhere on the planet that they can establish a Skype telephone call.  The captioner and the audio engineer at the live venue establish a Skype call so that the captioner can hear the live audio from the venue in real time.  Sitting at their stenography machine the stenographer then types the captions as the audio comes in. The big difference here is where the output of the steno machine goes. It goes to a web based service that the stenographer connects to and feeds the captioning output directly to the web service. Back at the live venue, the technical director watches the live captioning coming back to the venue from the web service over the Internet and injects the captioning using wipe techniques in the video switcher to insert the captioning in the bottom of the screen.

Voila’ you are done. Here are a couple of more things you need to know about captioning a live event for broadcasting over the Internet. There is no such thing as “closed captioning” over the Internet. Closed captioning means that a viewer can turn the captioning off and on while watching a broadcast. This is usually done by a set top box connected to your television. Over the Internet the captioning is always on with no way to turn it off. The captioner can only type what they hear so audio quality via Skype is of paramount importance.  How the technical director frames camera shots is directly impacted by the captioning at the bottom of the screen. Another thing to be aware of is that these web based services that the captioners send their feeds to have the ability to modify, fonts, font colors, sizes and backgrounds. Most of our customers prefer white text on a black background with a san serif font. This improves readability.

Finally, provide your captioners with a glossary of terms and acronyms that they can load into their steno machines before the broadcast. You should get a subject matter specific glossary from the client well in advance of the live broadcast date.

For those who are on-air talent the following rules when applied will improve the quality of the captioning and the broadcast:

  • When there are multiple speakers, try to distinguish when there is a change in speakers.
  • Speak directly into the microphone and speak as clearly as possible.
  • Keep your mouth the same distance from the microphone always.
  • Keep your speaking volume constant.

About the Author:

George Hall Founder/President of VideoSSC. He has over 30 years’ experience as a high technology engineering executive. With significant experience in high performance computing, Military electronics, IP networks and Video Broadcasting. Board member Public Television. An author and frequent guest on technology programs and panels. He holds a BA in mathematics from Hillsdale College.


  1. ig  February 16, 2015

    I could not resist commenting. Perfectly written!


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