August 2008

Working with Captions

By Mamta H. Tandel, Project Manager, BarrierBreak Technologies

Video plays an important role in the education, as it is increasingly utilized in Web-based learning applications. But, how many of these are accessible to people who are deaf or hard of hearing and senior citizens? Would people using mobile devices be able to access the audio content in a noisy environment? Is there a way to make prerecorded videos accessible to these people?

The answer is YES, through descriptions of audio, such as text transcripts, captions, or subtitles. In this article, we shall talk about captions and creating captions using Magpie.

Captioning is the process of converting the dialogues, music, as well as sound effects of a particular video into a textual format.

Well, you might have seen movies with text appearing at the bottom of the screen that is same as the dialogues spoken. These are nothing but descriptions of audio.

Captions are commonly referred to as subtitles. However, they quite differ from each other. Following are some differences between captions and subtitles.

Why Captions?

Captions are essential for people who are hard of hearing or deaf. Captions are also beneficial to those who find it difficult to understand the language and for people who suffer from situational disabilities such as users accessing information in a noisy environment. In addition, users browsing through the information using devices, which do not have speakers or headphones attached, will also benefit by reading the captions.

Accessibility laws and guidelines such as Section 508 and Web Content Accessibility Guidelines (WCAG) require Web content and related information to be accessible and emphasize on providing captions for the audio content in synchronized format.

WCAG 1.0:

Checkpoint 1.4 - For any time-based multimedia presentation (e.g., a movie or animation), synchronize equivalent alternatives (e.g., captions or auditory descriptions of the visual track) with the presentation (Priority 1).

Section 508:

§ 1194.22 Web-based intranet and internet information and applications- Guideline (b) Equivalent alternatives for any multimedia presentation shall be synchronized with the presentation.

Types of Captions

Captions are mainly of two types namely, Open and Close captions.

• Open captions are captions that are always visible and cannot be turned off.
• Closed captions are captions that the users can turn off or on depending upon their requirements.

How to Add a Caption?

There are different tools and technologies that allow adding captions to multimedia presentations, such as Windows Media player, Quicktime, RealPlayer, and Adobe Flash. Whether the audio content is prerecorded or live, captions can be provided to the presentation.

Magpie is one of the free tools available to add captions, which can be used across different media players. There are five steps that need to be followed to add captions in Magpie:

Step 1: Importing the Video File

To import the text in Magpie:

1. Launch Magpie.
2. Click 'File' and select 'New Project'. (The Properties window appears.)
3. In the General tab, in the 'Project Name' text box, enter a name for the project.
4. In the Media tab:
   • Click Browse and select the video file.
   • Set Time Unit to 100 milliseconds. (This helps us to give more accurate timecodes.)
5. In the Stream tab, set the following settings:
   • Current style name: Default caption
   • Font name: Arial
   • Font size: 12
   • Initial paragraph alignment: Center
   • Click 'OK'.

Note: The project will be saved with the extension .mag. The project includes a monitor to play the video and we can type in the text that should appear. In addition, the timing can be adjusted.

Step 2: Importing the Text

To input text in Magpie:

1. Click 'Stream' and select 'Import text'.
2. Select the transcribed text (.txt) file and click 'OK'.
3. Edit the text in the 'Caption' column.
4. Press Enter twice to separate two captions.

Step 3: Setting Timecodes

To enter timecodes:

1. Pause the video and press F9. (This will capture the timecode at that moment.)
2. Press F10 to enter a brief pause. (It enters the time code and a blank space in the caption.)

Note: Alternatively, you can enter the time in the HH:MM:SS.MS (hours: minutes: seconds. milliseconds format.) You can view the timecode in the monitor at the bottom.

Step 4: Saving the Stream

To save the Stream:

1. Click 'Stream'.
2. Select 'Save Stream As'.
3. Name the stream in the 'File name' text box.
4. Select 'Save Stream As'.
5. Click 'Save'.

Step 5: Creating the Output Files

Output files are files that tell the player which text to display at what time.

• Windows Media Player requires a SAMI file. To create a .smi file, click 'Output' and select 'SAMI'.
• Real Player requires a SMIL file. To create a .smil file, click 'Output' and select 'SMIL via Real Text'. (Note: Along with the .smil file, an .rt file gets created.)
• QuickTime Player requires a text (.txt) file. To create a text file, click 'Output' and select 'QuickTime'.

Note: The output files are saved in the same folder in which the project is saved. The most important point to be taken care of is the synchronization of text with the spoken words while captioning. Therefore, Step 3 above has to be done with full concentration. After creating the output files, they need to be integrated with the video.

In the next edition, we shall talk about adding captions using other technologies.