NCAM in the News

QuickTips: Captioning QuickTime

Michael Murie
DV.com Magazine

Using text tracks to add captions

QuickTime has supported adding captioning to digital video for some time with its text track capabilities, but few people bother to use it. This is a pity, as captioning can be useful both for those with hearing disabilities and for the general public.

It's surprisingly easy to create a caption track using QuickTime Player, provided you have QuickTime Pro. With the Pro version, the QuickTime Player's editing functions become operational.

A text track in QuickTime can be created using a text file. However, special formatting is required to handle the layout and the timing of the captions. Fortunately, QuickTime Player will help you by turning an unformatted text file into a correctly formatted one. This involves simply importing and then exporting the captions file. The exported file won't have the correct time stamps—QuickTime breaks the sentences into two-second segments—but once you have added the formatting, it's reasonably easy to go through and adjust the timing to match the video file.
Here's how to do it:

  1. Using a text editor (either Simple Text on the Mac, or NotePad under Windows), create a draft caption list that has each line of the caption on a separate line of the file.
  2. Open QuickTime Player and choose Import to import the text file. This will convert the file into a simple text track movie with a .mov extension name.
  3. Choose Export, and in the Export dialog, choose Text to Text as the export option.
  4. Click the Options button and choose Show Text, Descriptors, and Time, then click Export to export the text file.

This will result in a file that looks something like this:

{QTtext}{font:Geneva}{plain}{size:12}{textColor: 65535, 65535, 65535}{backColor: 0, 0, 0}{justify:center}{timeScale:600}{width:160}{height:48}{timeStamps:absolute}{language:0}{textEncoding:0}

[00:00:00.000]

Trip to Drumlin Farm

[00:00:02.000]

{child noise}

[00:00:04.000]

Hi kids!

[00:00:06.000]

This is our horse

[00:00:08.000]

she's about five years old

[00:00:10.000]

They're grooming her right now

[00:00:12.000]

The file now includes time stamps, but not necessarily the correct ones. The last task is to edit the text file again and adjust the time stamps to match the actual times in the movie. Using the Movie Info window in QuickTime Player, you can move through the original video, find the correct times for each caption, and then edit the timecodes in the file. Make sure the length of the movie matches the video file to which you want to add the captions. Finally, you re-import the text file using the QuickTime Player.

Editing the location of a text track in QuickTime Player
Editing the location of a text track in QuickTime Player.

The last part of the process is adding it to an existing QuickTime movie. To do so, copy the caption track by selecting all and choosing Copy. Then open the Video movie. Finally, choose Add Scaled from the Edit menu while holding down Shift-Ctrl-Alt (Windows) or Shift-Option (Mac).

This will paste the text track on top of the video movie. At this point, you will probably want to change the placement of the text track (and the matting). First, open the Movie Info dialog, choose the Text Track, and choose Size. Click the Adjust button and you can change the placementof the text relative to the video track. It's also possible to make the text background transparent by changing the Graphics Mode to transparent.

For a short movie, this process is pretty straightforward. But for long movies, it can become tiresome. Fortunately, there is a utility that can make the job simpler for Windows users.

Magpie

Magpie is a caption editor developed at WGBH's National Center for Accessible Media (NCAM). WGBH, the Boston public television station, has considerable experience in adapting television and video for people with disabilities. NCAM focuses on ways to make media more accessible to underserved populations such as the disabled and people with low literacy skills. The center's efforts include the development of CD-ROM and Web site accessibility guidelines that can be found at http://ncam.wgbh.org.

The Magpie application lets you open a video file and, using a grid-based interface, enter captions line by line. You can then play through the video and press a key to place the timecode at the appropriate points. The captions are even displayed along with the video. This is quicker, easier, and reduces the chances of transcription errors. Once the file is complete, it can be exported to the appropriate format and then added to the video.

Editing captions in the MAGpie application
Editing captions in the MAGpie application.

Magpie creates captions for three formats: QuickTime, Real, and Windows Media. All three formats support text, but they do it through different mechanisms. QuickTime uses its Text Tracks, Real uses RealText (and SMIL), and Windows Media uses the HTML Synchronized Accessible Media Interchange (SAMI) format. Unfortunately, the three caption formats are not interchangeable, and are not understood by other players.

According to Geoff Freed, project manager of the NCAM Web Access Project, each technology has advantages, so there's no clear choice.The biggest problem, according to Freed, is ignorance—designers don't know they can do captioning.

One advantage of QuickTime is that its text tracks are searchable, making it possible to find locations in long clips. It's also easy to add color and change the placement of text in QuickTime movies, though you can use Magpie to add color to text in the other formats.

For Mac-based QuickTime users, there are two problems with the current version of Magpie. First, it only runs under Windows. Second, the playback environment uses the Windows Media Player. Although Windows will attempt to open QuickTime files, it can only play video compressed with older compressors (i.e., Cinepak). It cannot open Sorenson files. To use Magpie, I first used QuickTime Player to convert a Sorenson-compressed movie to the AVI format, then used that file for the captioning process.

WGBH is working on an update to Magpie, and hopes to have a Macintosh version too. The big change for the next release will be greater support for audio descriptions. The current version supports adding audio descriptions (additional audio files with descriptions of the action occurring on-screen), but only supports SMIL output, and only works for Real's implementation of SMIL. The next release will, I hope, fix that. One concern is that QuickTime and SMIL support extra audio tracks very easily, but Windows Media Player and SAMI currently do not.

Distribution

Once you've added additional text and/or audio tracks, you have to decide how to distribute them. If the video is being played using QuickTime Player (either from a CD or downloaded), the user can simply turn the additional tracks on and off. But if the video is being played within a Web page, the current QuickTime plug-in does not let users turn tracks on and off. For this reason, you have to either leave the tracks enabled or serve multiple versions of the video. Let's hope this will be fixed in future versions of the plug-in. And just in case users don't already know, you may want to tell them about the Find feature in the player.

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