Closed Captioning on the Internet

Here is the summary of the lecture I presented during the centennial anniversary celebration of Philippines School for the Deaf last December 2007.

Closed Captioning is one of the important priority recommendations of Web Accessibility Initiative of World Wide Web Consortium or W3C (Priority 1-1.3 and 1-1.4) and of Philippine Web Accessibility Group Maturity Stage 1-5.

If you have AUDIO content in your website, provide written transcriptions of it. Let’s say, if an audio link of your company’s official anthem can be heard from your website, create a separate web page where the lyrics of the song can be read.

This can also be true with VIDEO clips. You may include closed captions at the bottom while the video is being played so that a deaf person can understand the conversations.

Now, what is a closed caption?
Closed caption is a text that is displayed often at the bottom of a video display that transcribes speech and other relevant sounds. As the video plays, caption describes all significant audio content and non-speech information, such as the identity of speakers and their manner of speaking, along with music or sound effects using words or symbols.

How does it help the persons with disabilities?
Closed captioning symbolized as CC, allows people who are deaf or hard of hearing to read a transcript or dialog of the audio portion of a video, film or other presentation.

Are there other people who can benefit from closed captioning?
Aside from the hearing impaired users, other people can benefit from closed captioning. These include:

  • People who want to learn new language;
  • People who are starting to learn how to read;
  • People who are in a noisy environment;

There are also some hearing people that suffer from the Central Auditory Processing Disorder. It means they confuse human voices with background noises as well as determining direction of the sound.

What is the difference between Closed Caption and Open Caption?
The term “closed” in closed captioning means that not all viewers see the captions—only those who decode or activate them. This distinguishes from “open captions,” where all viewers see the
captions, calling permanently visible captions in a video, film, or other medium “open”, “burned-in” or “hard coded” captions.

Closed caption should not be confused with subtitling although they often interchange. SUBTITLES are what we often see on DVD-Movies. Like CC, they are also seen at the bottom of the screen during
dialogues. However, subtitles can be translations of the dialogue in a foreign language while closed caption are direct transcription of speeches.

How do I put closed captions in video files?
There are two media formats that can be used in creating closed captions. One is the Synchronized Accessible Media Interchange or SAMI developed by Microsoft to be compatible with their Windows Media Player (.wmv) format. The .smi file is created to synchronize with the video. The other one is Synchronized Multimedia Integration Language or (SMIL). It is a W3C Recommended XML markup language for describing multimedia presentations. SMIL is considered as an industry standard. This language can be used on other non-Microsoft popular formats like RealPlayer (.rm), Apple Quicktime (.mov) or MPEG (.mpg or .mp4) files. It also creates a .sml file to synchronize with the video. SMIL works in all browsers including Internet Explorer while SAMI can only be viewed exclusively in IE.

Adobe Shockwave Flash videos can also be closed captioned. But the technique in putting one is by embedding it inside the flash file itself.

Windows Media Player does not support audio descriptions at this time. So the closed caption appears outside the screen and can only be synchronized as an object embedded format in a web page. RealPlayer and Quicktime formats place the closed caption inside the screen.

There are companies that create closed captions for a fee. However, there is a free software can be used to create the closed caption. It’s called Magpie 2.0 created by the The Carl and Ruth Shapiro
Family National Center for Accessible Media (NCAM). It is a research and development facility dedicated to the issues of media and information technology for people with disabilities in their homes,
schools, workplaces, and communities. You can visit their site and download their software at:

On my next blog entry, I will post an example of a close captioned video file.

Blog at

Up ↑