The Journal for Undergraduate Multimedia Projects



The Journal for Undergraduate Multimedia Projects

Descriptions of Captioning Accessibility Technologies:

How do they function with varying computational interfaces?

Working Document

Captioning Technologies

Synchronized Accessible Media Interchange (SAMI)

“In 1997, when no standard for closed captions in digital media existed, Microsoft developed Synchronized Accessible Media Interchange (SAMI) and implemented it in Microsoft Encarta Reference Suite, Windows Media Player, and Microsoft DirectShow application programming interface.

Concurrently, members of the World Wide Web Consortium (W3C) created Synchronized Multimedia Integration Language (SMIL), which can be used for closed captions. Microsoft Internet Explorer supports the latest version, SMIL 2.0, creating a synchronization framework based on it called HTML+TIME.

In practice, to attempt to integrate captions into an existing, fully synchronized SMIL 2.0 media file is sometimes costly. In contrast, a SAMI document contains only closed captions text; it can be edited separately from the media file and requires fewer programming skills.

SAMI simplifies captioning for developers, educators, and multimedia producers and designers who will now find it easier to make their work more universally accessible. The SAMI file format specification is available to the public as an open (no licensing fees) standard.” [i]

“SAMI is a Microsoft public specification that allows closed captions to be played in the Windows Media Player on the Windows OS only. When the Windows Media Player is used as a stand-alone player, viewers can turn the captions on and off using a menu selection. However, when the player is embedded in another application, such as a Web page, the developer must provide the toggling feature through a button in the application's interface. For additional flexibility, this interface can also provide options to change the font size or text color.

At the time of this writing, SAMI does not support closed audio descriptions. Instead, descriptions must be recorded permanently as open descriptions directly into a video's regular soundtrack. If this approach is used, authors should also provide a separate version of the video with the original program audio (without audio descriptions).”[ii]

“For details about the SAMI format and the platforms, see the MSDN Library. Examples are also available in the MSDN article Understanding SAMI 1.0.”[iii]

Synchronized Multimedia Integration Language (SMIL)

“Internet Explorer supports SMIL 2.0 as part of HTML+TIME implementation. For details on the specification and examples of HTML+TIME see the MSDN Library. For more information on SMIL 2.0, see the W3C recommendation, and W3C Synchronized Multimedia page.”[iv]

“SMIL is played by the QuickTime Player, RealPlayer, the Oratrix GRiNS Player and the Ambulant Player. SMIL multimedia presentations are made up of elements-sound, video, pictures and text that are stored separately and then synchronized at the time of playback. SMIL-formatted multimedia can be delivered via the Internet or a local file system via hard drive, CD or DVD. Visit the W3C's Synchronized Multimedia page for complete information about SMIL and related activities at the W3C.

When authored correctly, SMIL allows users to turn captions and descriptions on and off via a player interface. The QuickTime Player, GRiNS Player, Ambulant Player and RealPlayer each provide a menu selection or dialog box for this feature, but for better accessibility authors should consider adding accessible buttons to the player interface for easier toggling of tracks. In fact, this is crucial when embedding a player into a Web page.

SMIL provides test attributes that can be used to programmatically determine, among other things, the viewer's player preferences for captions and descriptions. The RealPlayer and Ambulant Player, for example, support the SMIL test attributes for captions (systemCaptions) and descriptions (systemAudioDesc), while the Quicktime Player does not.

You can use MAGpie to author accessible SMIL presentations, but if you wish to write SMIL code yourself, details are provided on the NCAM website. The RealPlayer and Ambulant Player provide reliable support for the current SMIL recommendation. Support for SMIL in the QuickTime Player is selective, so test your presentation thoroughly before making it available publicly. Also read about QuickTime's support for SMIL at Apple's Developer Connection site.

Take note that different SMIL players provide varying levels of implementation-- in other words, some players implement the entire specification, and some use only parts of it. Also, not all of SMIL's accessibility features are supported by all SMIL players. In these cases, we offer workaround solutions that will work with existing players.”[v]

Open Captions

“Open caption is text embedded directly in the video screen. Open captions do not require a caption decoder in the media player.

In a computer environment, open captions are simply an additional track that is added at the end of a video production process. They are embedded in the media file itself, and therefore are readable by any player. For example, any MPEG movie that contains open captions can be played in any multimedia player with MPEG decoder support.

For computers, you need a browser (for example, Microsoft Internet Explorer) or player (for example, Windows Media Player) that can decode, or parse the caption text, which is stored in an additional file.

Use open captions when:

• You are not sure that your media file(s) will be read by a browser or player that can read the caption text.

• You are not able to specify which player will be used. Because there are competing standards and implementations, it may be too costly to create caption text for multiple players.”[vi]

Captioning Options for Various Streaming Media Players

Stand-alone Players

Display the video in a separate window outside of the Web browser

Popular options: Windows Media Player, Real Player, and QuickTime

Embedded Players

Display the video inside of a Web page

Popular options: Flash-based (e.g., YouTube and Google Video); Java-based (e.g., Clipstream) players; several other new competing players and formats (e.g., Microsoft’s Silverlight technology, though it is currently limited to the Microsoft Windows and Apple Mac operating systems)[vii]

Challenges of Captioning for Various Players

Each of the various streaming media players requires specially formatted caption files. Windows Media Player, Real Player, and QuickTime, for instance, all have their own special requirements for the makeup of these files, how they are named, and where they go in conjunction with the video file. Video producers will need to research the various players and formats before deciding which ones are right for their needs.[viii]

Adobe Flash

“The Flash-based video format, by Adobe Systems, Inc., is used on thousands of Web sites around the world and has become the de-facto standard for video and multimedia content on the Web. Streaming video sites such as YouTube and Google Video have popularized the format due to the ease of player installation, support for multiple browsers and operating systems, and a video compression technology that offers VHS-or-higher quality using a relatively small amount of bandwidth. The installation process for the Adobe Flash player is accomplished via a small plug-in for your Web browser which takes only a few mouse clicks to install.

Adobe provides a number of accessibility options for Flash video using the Distribution Format Exchange Profile (DFXP) of the timed text authoring format to embed subtitles into the video file. To learn more about creating captions for the Flash format, visit the National Center for Accessible Media’s (NCAM) CC for Flash Web site. You can download the free CC for Flash captioning tool, which will allow you to either create a new caption file or import an existing caption file from any of several different formats for use in a Flash video. Additionally, you can learn more about efforts underway to create an Internet Captioning Forum (ICF) at the NCAM Web site. The ICF is being developed to help coordinate captioning technologies between the various multimedia vendors on the Internet. This exciting new initiative has the potential to bring a wealth of new captions and interest in accessibility to the streaming media format. To learn more about providing captions for Flash media, and to keep up with the latest developments in Flash player accessibility, visit Adobe’s accessibility blog. Be sure to visit the DCMP accessibility search gateway to learn more about the tools and practices involved in adding captions for whichever media format(s) you choose.”[ix]

Caption It Yourself (CIY): subtitling/audio description software tools

Media Access Generator (MAGpie)

“Web-based video and audio clips can now be made accessible to users who are disabled and non-English speakers with a complimentary captioning/subtitling and description software tool--callled MAGpie--developed by the Media Access Group at WGBH. User-friendly for educators, young users and those new to multimedia, MAGpie allows authors to add captions, subtitles and audio descriptions to the three most popular digital multimedia formats:

• Apple's QuickTime Player

• RealNetworks' RealPlayer

• Microsoft's Windows Media Player” [x]

“MAGpie can be used to create captions and audio descriptions for SMIL presentations, and captions only for SAMI and Adobe Flash presentations. Both regular and extended audio descriptions can be digitally recorded and integrated into a SMIL presentation using NCAM's free utility, MAGpie 2.01. You may also use any sound-editing program, such as SoundForge or Audacity, to record the audio files, and then use MAGpie to integrate them into an accessible presentation.

The easiest method for adding captions to multimedia presentations is to use MAGpie. MAGpie allows authors to write captions once and output them in formats for RealNetworks' RealPlayer, Oratrix's GRiNS Player, Apple's QuickTime Player and Microsoft's Windows Media Player. These players each use proprietary text-display formats, so captions that play in one player will not play in another (except for the GRiNS Player, which plays RealNetworks' RealText format). Read complete information on using MAGpie to create and synchronize captions on the MAGpie Web site.

As of this writing, there are serious shortcomings with the display of scientific and mathematical expressions in captions. No standard method exists for displaying complex math or science notation within multimedia players. (Existing mathematical markup languages, such as MathML, are not yet supported in multimedia players.) Therefore, representing anything beyond simple mathematical expressions in captions can only be accomplished via text.

Research and development efforts will eventually simplify the creation and display of scientific and mathematical expressions in captions. The W3C is currently defining a standard timed-text format that could eventually be adopted by multimedia player manufacturers” [xi]

“For additional information about MAGpie's features and capabilities, and to download the free software, visit .”[xii]

“MAGpie 2.5.1 contains the following updates:

• An export selection for the TTXT format, which can be used to add closed captions to movies playable on BlackBerry® smartphones.

• An export selection to automatically combine (or mux) TTXT caption files with MP4 or 3GP source files. These closed-captioned videos can be played, and the captions decoded, on BlackBerry smartphones.

As before, you can use MAGpie to create caption files for YouTube videos.

MAGpie is a Java2 application which runs on Windows 9x/NT/2000/XP/Vista/Windows 7. Please note that MAGpie 2.5.1 removes support for the GRiNS player. If you are currently using GRiNS to caption RealMedia source files, do not replace your current version of MAGpie with version 2.5.1. (MAGpie 2.5.1 will still export SMIL files for the RealPlayer, however.) Windows Media clips cannot be used as source files except with MAGpie 1.0.”[xiii]

The JW Player for Flash. “It's one of the few players that can display both closed captions and a closed audio description. Since it is built in Adobe's Flash, 95-99% of your visitors will be able to watch it.

Other accessibility features of this player are its keyboard controls (using the TAB and SPACE controls), its screen reader-labeled buttons and the full-screen button. Also, immediately above the player, hidden controls allow screen reader users to control the basic functionality of the player (Play / Mute / Stop).

This example uses the SWFObject JavaScript to detect if your visitors have the right Flash plugin (and JavaScript) installed. If so, the player is shown. If not, the player falls back to show an image linking to a downloadable video file. You can see a demonstration of how this works by turning off your browser’s JavaScript and reloading this page. Again, both the image and link have a text label for screen readers.

Note that the downloadable video file is an MP4. This is a high-quality format, which is very popular among mobile devices such as iPods / iPhones, the PSP and many smart phones. The MP4 format, though, isn't very useful if your target audience has older browsers or devices. It's fairly new and isn't supported by the default Windows installations. If your goal is to maximize reach, it’s best to encode any download as an MPG; its quality relative to file size is poor, but it’s able to play on just about everything. If you want to maximize accessibility even further, you can always hard code the captions and audio description into the video.

There's a whole range of applications that can transcode your original video files into any format you’d like (e.g. FLV, MP4, WMV, MPG).

1. NCAM's magPIE (free, also for MAC)

2. URUSoft's Subtitle Workshop (free)

3. Manitu Group's Captionate ($60)

4. VideoToolShed's SubBits subtitler ($199)

Both magPIE and Subtitle Workshop support the export of captions to W3C's TimedText (Flash), SMIL/QTtext (Quicktime) and ASX/SAMI (Windows Media). For Subtitle Workshop you need the TimedText output script (available from Naomi Spirit). Captionate, (intended for FLV video) can only export to W3C's TimedText, though it can also save captions as metadata.

Only magPIE has support for recording audio descriptions, but it’s somewhat limited. You cannot record to MP3 and cannot merge recorded samples or integrate them with a video. For now, a full-fledged audio/video suite, like Adobe's Premiere / Audition or Apple's iMovie/GarageBand, is needed for creating closed audio descriptions.”[xiv]

“CCforFlash, a free Flash component that can be used to display captions of Flash video and audio content”[xv]

“CCforFlash is a component that is added to your Flash project to display captions. If you are not a Flash programmer and need a pre-existing media player that already has CCforFlash inside it, check out NCAM's Flash-based media player, ccPlayer.

CCforFlash is used to display captions with Flash video and audio content. These captions are stored in external files formatted in the W3C's DFXP format which can be created with MAGpie, NCAM's free captioning application. CC for Flash can also display captions saved in Apple's QTtext format. QTtext files can be created by professional caption authoring tools, with MAGpie or with CaptionKeeper, NCAM's line-21 caption-conversion tool.

The CC for Flash component is customizable and allows authors to set defaults, such as the width and height of the caption area, the caption area's background and text colors, the opacity of the background (for placing captions over the video), and the font family and font size of the captions themselves.

Other features include:

• access to captions stored internally in the Flash movie or embedded in the FLV video file;

• caption search, returning the timecodes where text strings occur;

• roll-up caption display;

• switching between multiple languages of captions that have been stored in the same DFXP file;

• ability to provide parsed caption data to other objects in the Flash movie;

• manual operation where a timecode is presented and the corresponding caption is displayed (AS3 version only).

For those who are not handy with Flash programming, NCAM has created two flexible players which ease the process of providing captioned Flash video and MP3 audio files: ccPlayer, incorporating the CC for Flash component, allows you to embed a FLV player on your Web page; ccMP3Player, which also incorporates the CC for Flash component, plays back MP3 files in a Web page with corresponding caption files. Both players are accessible to screen readers and can be operated solely from the keyboard.”[xvi]

“ccPlayer and ccMP3Player, free players that incorporate CCforFlash components; useful for non-Flash authors who want to add captions to Flash video or audio, respectively”[xvii]

“CaptionKeeper, software that converts television closed-caption data into Web streaming formats”[xviii]

Web-based Captioning/Subtitling Tools

CaptionTube The latest CIY tool, CaptionTube has a clean (and simple) user interface and multi-language capability similar to many of the other resources identified below. It is slightly more integrated with YouTube than the others, and features a convenient export tool which allows you to e-mail the captions to a video’s owner (if you’re captioning for someone else) or download a .SUB or .SRT file. A CNET review of CaptionTube (which includes a couple video tutorials) provides a handy introduction to the service.

TubeCaption An innovative YouTube “mashup” that actually pays you to caption. Sign up and begin captioning your favorite YouTube videos using the full-featured Captionizer captioning tool, which provides many useful features including: handy keyboard shortcuts, multi-language support, and the ability to import and export SRT files. As an added bonus for your effort, you get 50% of the ad Google AdSense revenues generated from your captions.

dotSUB Allows people from around the world to create caption files in multiple languages for streaming videos. The dotSUB caption file can be exported to a SRT format for use with Subtitle Workshop or Google Video (see below). dotSUB Repair is an online script that replaces missing zeroes in SRT files exported from dotSUB and Overstream. Use this tool to repair your SRT file before uploading it to Google Video or importing it to Subtitle Workshop.

Overstream Provides a graphical interface for creating captions. The Overstream Editor allows the user to export a SRT file which can be uploaded to Google Video to provide closed captions, or converted to Timed Text XML using Subtitle Workshop, Subtitle Horse, or MAGpie.

Subtitle Horse A tool for transcribing Flash videos online and exporting/converting a caption file in several different formats including the Timed Text XML format used by multiple video players including both the Adobe Flash and Microsoft Silverlight players. (Subtitle Horse was used to convert timing information for Equal Access in the Classroom's Timed Text captions)

Easy YouTube Caption Creator A simple tool (designed for easy of use in mind) used to create captions for YouTube videos. Read about Easy YouTube Caption Creator on the Accessify blog or watch the Easy YouTube Caption Createor Screencast, also from Accessify.

“Bear in mind that none of these free captioning sites and tools will make it possible to create captions which conform to the DCMP Captioning Key. Creating captions with the proper font style, color, and placement characteristics required to meet the Captioning Key’s rigorous guidelines involves more extensive tools and techniques than those covered here. As streaming video player caption technologies continue to evolve, the DCMP will provide more information and tutorials on our site to assist parents, educators, and others in creating “DCMP Approved” captions to benefit learners of all ages and abilities.”[xix]

Universal Subtitles: Works with Vimeo, YouTube, , h.264, HTML5

“It's powered by viewers and other volunteers: it's collaborative editing and translation, like a wiki. It's the world's easiest subtitle creator - type and tap. The fastest way to add subtitle functionality to a single video or a whole site. Super easy to integrate with no software to install. Free, open-source, and non-profit!”[xx]

Desktop Captioning/Subtitling Software

CapScribe (free) A new, open source application for adding captioning and video description to web and desktop video and audio files. While the editor requires a Mac (OS 10.3 and greater), your edited content will play back on both Mac and Windows. Quicktime 6.5 or greater is required for playback on Macs and Windows. (A Web-based version of CapScribe is currently under development.) A series of CapScribe tutorials (video/PDF/etc.) are available from the University of Toronto’s Adaptive Technology Resource Centre.

Captionate A desktop application for captioning Flash videos. The caption output can be displayed using either the JW FLV Media Player or the Adobe FLVPlayback skin.

CC For Flash (free) A Flash component that can be used to display captions for Flash video and audio content, as well as caption files saved in Apple’s Quicktime QText format.

Jubler (free and open source) (Linux, Windows, and Mac) A Java-based tool for creating captions and subtitles in a variety of formats (installation can be tricky on Windows machines—Luckily, there is a step-by-step Jubler installation guide available.)

MacCaption Works with Final Cut Pro or any Non-Linear Editing (NLE) system to produce captions for multiple formats and players. No closed captioning hardware required.

MovCaptioner (Mac only [Windows version in development]) Utilizes a GUI to create and synchronize captions in a number of popular formats. Single- and multi-user licenses available.

Subtitle Workshop (free) (Windows only) The most complete, efficient and convenient freeware subtitle editing tool. It supports all the subtitle formats you need and has all the features you would want from a subtitle editing program.[xxi]

Caption-Ready Video Hosting Providers

YouTube Google has launched its “auto caption” feature for new YouTube uploads by which text-to-speech software (of the type used by Google Voice) will attempt to automatically generate captions from a video’s soundtrack. If you’d like slightly more control over the content of your captions, Google has also implemented “automatic caption timing.” To use this feature, simply transcribe all of the words found in your video, and upload it as you would your SRT (timed) caption file (see below). The same text-to-speech algorithms used for “auto caption” will synchronize your transcribed text for you, eliminating the need to worry about timecodes. (Check YouTube help for more about these automatic features.)

However, the safest (and most accurate) bet would be to upload an SRT file with your video; once completed, this will enable a “CC” button on the video player interface and captioning will be turned on by default. YouTube has provided instructions for users interested in adding captions to their YouTube videos.

Overstream Users can create, import, and export a SRT file with their video. The SRT “overstreams” are displayed along the bottom of the video during playback.

dotSUB Users can create, import, and export a SRT file with their video. Captions are displayed on the video during playback. Captions can be turned on or off using up and down arrow buttons.[xxii]

Notes

-----------------------

[i] "Captions and Audio Descriptions for PC Multimedia." MSDN . Microsoft Corporation, 22 Mar. 2010. Web. 27 Jan. 2011. .

[ii] "Invent + Build/ Web + Multimedia/Accessible Digital Media Guidelines/Guideline H: Multimedia/NCAM." The WGBH Carl and Ruth Shapiro Family National Center for Accessible Media. Media Access Group at WGBH, 2009. Web. 27 Jan. 2011. .

[iii] "Captions and Audio Descriptions for PC Multimedia."

[iv] Ibid.

[v] "Invent + Build/ Web + Multimedia/Accessible Digital Media Guidelines/Guideline H: Multimedia/NCAM."

[vi] "Captions and Audio Descriptions for PC Multimedia."

[vii] Kevin Jones, "An Introduction to DVD and Web Captioning." Described and Captioned Media Program. U.S. Department of Education, Nov. 2008. Web. 27 Jan. 2011. .

[viii] Ibid.

[ix] Ibid.

[x] "MAG Guide, Vol. 13." WGBH Media Access Group. WGBH Educational Foundation, 2011. Web. 27 Jan. 2011.

[xi] "Invent + Build/ Web + Multimedia/Accessible Digital Media Guidelines/Guideline H: Multimedia/NCAM."

[xii] "MAG Guide, Vol. 13."

[xiii] "Invent + Build/ Web + Multimedia/Tools & Guidelines/MAGpie home/NCAM." Carl and Ruth Shapiro Family National Center for Accessible Media. Media Access Group at WGBH, 2009. Web. 11 Feb. 2011. .

[xiv] "Making Video Accessible: LongTail Video: Home of the JW Player." Advertisement. LongTail Community. LongTail Ad Solutions, 2010. Web. 27 Jan. 2011. .

[xv] "Invent + Build/ Web + Multimedia/ Tools & Guidelines/ NCAM." The WGBH Carl and Ruth Shapiro Family National Center for Accessible Media. Media Access Group at WGBH, 2009. Web. 27 Jan. 2011. .

[xvi] "Invent + Build/Web + Multimedia/ Tools & Guidelines/ CCforFlash/NCAM." The WGBH Carl and Ruth Shapiro Family National Center for Accessible Media. Media Access Group at WGBH, 2009. Web. 12 Feb. 2011. .

[xvii] "Invent + Build/ Web + Multimedia/ Tools & Guidelines/ NCAM."

[xviii] Ibid.

[xix] Bill Stark, dir. "Caption It Yourself: Basic Guidelines for Busy Teachers, Families, and Others Who Shoot Their Own Video." Described and Captioned Media Program. U.S. Department of Education; National Association of the Deaf, 21 Apr. 2010. Web. 11 Feb. 2011. .

[xx] "Universal Subtitles--Make Subtitles, Translations, and Captions for Almost Any Video." Universal Subtitles. Participatory Culture Foundation, n.d. Web. 12 Feb. 2011. .

[xxi] See Bill Stark’s guidelines.

[xxii] Ibid.

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