Skills for Access

Why this is important

Providing captions enables media that contains spoken or other audio information important to understanding the media's content (for example on-or off-screen dialogue, sound effects, or background music) to be accessible to anyone who is deaf or hard of hearing or otherwise unable to hear the media soundtrack. Any content intended for playing in QuickTime must as a result offer captions to be optimally accessible for these users.

General Principles

Captioning for QuickTime can be done in three ways:

1. If you have QuickTime Pro, you can create a single QuickTime file containing the video clip plus captions (and audio descriptions).
2. Or, you can create a separate caption file, and use SMIL to combine this with the QuickTime movie. This can be done without requiring the QuickTime Pro software.
3. Or, you can use captioning software such as MAGpie to caption a Quick Time file.

NB The facility to turn on or off captions and audio descriptions is only available in QuickTime Pro, and currently not the free player. Thus, if you can't be certain that your target audience will be using QuickTime Pro, and you'd rather not provide the media with captions turned on by default, then we suggest you offer multiple versions of your media:

1. Video and audio;
2. Captioned video - with described audio if provided;
3. Audio plus audio descriptions as a sound file (for example MP3);

NB: We have provided general advice on captioning in a separate How To: Provide text equivalents for audio - general advice on captions.

Before you continue

The advice on this page helps you avoid introducing a specific accessibility barrier, but it's not a magic formula. To avoid attempting to follow a technical solution that is not appropriate to the resource and its intended purpose, you need to know the context in which the multimedia resource is being used:

1. The purpose or aim of the multimedia resource in question, and whether it is being used to supplement another resource in the learning environment, or whether its use is required by students.

2. The target audience, their knowledge and expectations, and the type of browsing and assistive technology that they may be using.

3. Whether the information and experiences provided by the multimedia technology are already available in an equivalent, alternative form.

For more background on this approach, see our Guide to the use of multimedia in accessible e-learning.

Technique Details

The procedure of creating and making available a captioned QuickTime video file is as follows:

Step 1: Create a QuickTime Text (QTtext) caption file, a simple text file, with extension .txt. The file contains the caption text, plus timestamp detail (the time at which each specific piece of caption text is displayed - essential for synchronised captions). Other attributes can also be specified in the QTtext file, including size of the window containing the captions and appearance of the caption text. You can create a QTtext file using software such as MAGPie, or manually using a text editor and QuickTime Pro.

To obtain timestamp detail, you must play the video, pausing and noting the time at which each caption will appear. If you have a transcript file already, the time taken and effort required to create captions is reduced, as you can then focus on splitting the transcript text into appropriate captions, and applying a timestamp to each. If you don't have a transcript you'll have to create this first by playing the video and writing down spoken and non-spoken sound information.

Example 1 is a sample of code from a QT text file used to provide captions for a QuickTime video clip:

{QTtext}{timescale:100}{font:Verdana}{size:14}{backColor:0,0,0}
{bold}{textColor:65535,65535,65535}{width:320}{justify:left}

[00:00:00.00]
"Access for All" came about 
because obviously DDA

[00:00:03.57]
and SENDA were both 
introduced and that

[00:00:07.59]
accompanied a perceived 
inaccessibility of multi-media.

[00:00:11.02]
The project 
specifically is looking at

Example 1: QT Text sample code.

If you use QuickTime Pro to caption your movie, open the movie to be captioned in QuickTime Pro, and progress through the movie, playing and pausing, as you create the QText file in a text editor. Use the player's Movie Properties feature to find and copy precise timestamp detail to each caption in the QTtext file (in fact this feature is also available in the free QuickTime player).

Step 2: Combine the caption file with the movie. How you do this depends on whether you're using QuickTime Pro to create a combined captioned movie, or SMIL.

If using SMIL, you can create a SMIL (.smi) file either by hand in a text editor, or in authoring software such as MAGPie. In this file, you must specify the QuickTime video (.mov) file being captioned and the QTtext caption file you've just created. You can also provide information about the size of the window containing the captioned movie, as well as properties of the window region showing the video and the region showing the captions. You do not have to convert the caption file into a QuickTime movie (unlike when using QuickTime Pro).

Example 2 shows a portion of the SMIL file used to combine the QT Text file shown in Example 1 with a QuickTime video clip.

<?xml version="1.0" encoding="UTF-8"?>
<smil xmlns:qt="http://www.apple.com/quicktime/resources/smilextensions" xmlns="http://www.w3.org/TR/REC-smil" qt:time-slider="true">

<head>
<meta content="" name="title"/>
<meta content="" name="author"/>
<meta content="" name="copyright"/>

<layout>
<root-layout width="330" height="335" background-color="black"/>
<region top="5" width="320" height="240" left="5" background-color="black" id="videoregion"/>
<region top="245" width="320" height="80" left="5" background-color="black" id="textregion"/>
</layout>

</head>

<body>
<par dur="0:01:23.00">
<video dur="0:01:23.00" region="videoregion" src="/media/rlvidq1_220k.mov"/>
<textstream dur="0:01:23.00" region="textregion" src="/media/rlvidq1_qt.txt"/>
</par>
</body>

</smil> 

Example 2: Sample of SMIL file.

If using QuickTime Pro, when the QText file has been created, it needs to be converted into a QuickTime movie. This can be done by opening the QTtext file in QuickTime Pro and saving it as a QuickTime movie (.mov) file. Some adjustments may be required to make sure that the captions display appropriately. If using QuickTime Pro, the caption movie must then be combined with the video. Again, this is done in QuickTime Pro, - open the caption movie first, select all, copy, then open the video file and add the selected caption movie. Adjustments should also be made to the position of the captions relative to the video, and when everything is satisfactory, save as a self-contained movie.

Whether using QuickTime Pro or SMIL, the process of successfully synchronising captions with the movie will be an iterative one. You'll probably have to spend some time adjusting timestamps and the text displayed at each timestamp. Just keep editing the caption file, recombining with the video and checking over until everything is satisfactory.

Step 3: Make the captioned QuickTime video available from a web page - to do this depends on whether you plan to make the captioned media available embedded within the page, or in a stand-alone player (generally preferred for accessibility reasons):

Stand-alone captioned QuickTime movie: Use the HTML object and <embed> elements are used, with the non-standard <embed> element enclosed within the <object> element. Because there are problems with QuickTime directly opening SMIL files, you need to create and reference a 'placeholder' movie file that will be opened by QuickTime - for example a .mov or .qti (a QuickTime image, i.e. a still from a QuickTime video) as well as the SMIL file or captioned .mov file. This 'placeholder' file is opened first by QuickTime, which then opens the referenced SMIL file (or captioned .mov file). Alternatively, but less widely supported, SMIL-captioned QuickTime files can be opened via a QuickTime Link file.

Clip 1 is an example of a captioned QuickTime video clip, which uses the QT Text file and SMIL files shown in Examples 1 and 2:

Embedded SMIL-captioned QuickTime movies also require using the <object><embed> code, with slight differences to the code used for stand-alone players.

The above provides an outline of the process of creating a captioned QuickTime movie. For a detailed, step by step tutorial on how to caption and make available on-line a QuickTime video file using either QuickTime Pro or SMIL, we recommend WebAIM's tutorial on QuickTime Captioning.

Testing

The process of creating an appropriately time-stamped caption file should ensure that captions are synchronised with the video clip. However, it's always a good idea to check that your captions are displayed and synchronised appropriately in QuickTime by playing the captioned file with audio turned on. This way, you can detect any clear inaccuracies, missing content or problems with synchronisation.

If provided, captions should automatically be displayed when an embedded or standalone QuickTime movie is launched (with the free QuickTime Player, you will be unable to turn them off - only QuickTime Pro Player has the ability to turn captions off or on.). To toggle on or off captions or soundtracks in QuickTime Pro version 6, in the 'Edit' menu select 'Enable tracks'. This gives you a list of tracks, including the text track(s) containing captions. Deselect a track to turn it off. Note that there may be many tracks to deselect, particularly if the movie has several audio description files added to it.

It would also be worthwhile obtaining feedback from end users, particularly people who are deaf or hard of hearing - although they, of course, will be unlikely to know whether the captions are a true reflection of the audio content of the media clip.