Multimedia Glossary

Alternate Closed Caption logo without letters

Contents



Camtasia Studio
A software tool used for screen capture and video captioning. See Adding Captions in Camtasia Studio and screen capture entry below.

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Caption Style Guide
The guidelines described in these tutorials are adapted from the Described and Captioned Media Program’s (DCMP) Captioning Key. The DCMP is funded by the U.S. Department of Education and administered by the National Association of the Deaf. We have found these guidelines to be comprehensive. For additional information, follow the link to the Captioning Key website: http://www.dcmp.org/captioningkey/.

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Captions
Captions are textual versions of the spoken word. Common accessibility guidelines indicate that captions should be:
  • Synchronized — the text content should appear at the same time as the audio.
  • Equivalent — content provided in captions should be equivalent to the audio, including music lyrics and sound effects if they contribute to the meaning of the video.
  • Accessible — captions should be readily accessible and available.
Compared to subtitles, captions are designed primarily for viewers with hearing impairments. Thus they include more information than subtitles, which typically capture only the dialog. Captions, by contrast, include contextual information, such as sound effects, speaker identification and location (both inside and outside the field of view), and music lyrics.
  1. Closed Captions

    Standard Closed Caption logo with two C'sMost people are familiar with closed captions, which are displayed when desired, but are otherwise hidden or "closed" from view. Closed captions, denoted by the logos shown above, are a legal requirement for much of broadcast television. Closed captions are encoded in the TV signal and are displayed using a decoder that is built into the television. Closed captions are also increasingly available on the Web, where they are generated from a text file that includes time stamps for each caption, allowing synchronization with the video during playback.

    Computer videos such as MP4s may contain closed captions, but your ability to display them depends on the capabilities of your media player. Windows Media Player can display captions and subtitles when playing a DVD, but not when playing an MP4 video created from that DVD. The VLC Player, on the other hand, is able to display captions and subtitles in both DVD and MP4 video, when available. See the tutorial Converting DVD Videos to MP4 for instructions on how to preserve DVD captions and subtitles.

  2. Open Captions

    Captions that are "open" are a permanent part of the video image and cannot be turned off. The open caption approach promotes universal access and ease of use. It also assumes that many people will enjoy the benefits of having an alternative method of grasping the video's content. On the other hand, some people feel distracted or even annoyed by captions that are always on. The authors can attest to feeling frustrated when moments of dramatic tension are spoiled by captions that appear before the corresponding dialog is spoken. However, the same authors appreciate captions when dialog is difficult to follow, or when technical vocabulary is used in instructional videos.

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CODEC
As defined by Wikipedia, a codec is “a device or computer program capable of encoding and/or decoding a digital data stream or signal.” Just as the JPEG algorithm is a common compression/decompression method used for still images (photographs), a codec like H.264 is an algorithm used to compress moving images (video)—a similar but vastly more complex operation. Codecs reduce file size and allow content to play smoothly by throwing out much of the original video information. The H.264 codec is used to compress video in various container files, including MP4 files and Blue-ray discs.

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Copyright law protects the rights of anyone who creates an original creative work. Those rights include the ability to copy, distribute and adapt that work. Strictly interpreted, copyright law prohibits any conversion, copying, editing (including adding captions), or archiving of digital media by anyone other than the copyright owner. A "fair use" exception exists for educators, journalists, comedians and others, who are allowed to use portions of an original work for teaching and scholarship, news reporting, research, commentary, and parody.

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Descriptive Audio
Audio description is a term used to describe the narration of key visual elements in a video or multimedia product. The description summarizes any visual information, including action, settings, and characters that are necessary to understand the video. It can be both subjective and artistic, depending on the intentions of the author. Initially developed to assist Blind viewers in understanding key visual information in video broadcasts, descriptive audio may identify important aspects of a video that may be overlooked by sighted viewers. Students benefit the most when the description of the video is made available in both text and audio form. An example of descriptive audio can be seen in the ACCESS video.

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DVD Titles and Chapters
DVDs are typically divided into titles and chapters. A DVD title is usually an entire feature, like a movie or episode, while chapters divide the title into scenes. When you use your remote to jump from scene to scene, you are navigating a DVD by chapter.

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Fair Use
See Copyright Law.

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License
License is closely tied to copyright (see above). On YouTube, videos are set by default to the “Standard YouTube License," which does not grant permission to others to take or modify the original work. Recently YouTube added another licensing option, the “Creative Commons Attribution License,” which does allow others to modify the video (including adding captions) and save a copy of it to their own YouTube video library. Asking the owner of a YouTube video to change the license to "Creative Commons" is one method of gaining access to a video so that it can be captioned.

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Media Player
There are many media players available, each with its own strengths and weaknesses. Windows Media Player is ubiquitous on computers running a Microsoft operating system, just as the QuickTime Player is universal on Apple computers. Microsoft took a big step toward interoperability when it released Windows Media Player 12 (WMP 12), which was bundled with the Windows 7 operating system. After nearly two decades of inability to play Apple's media formats, WMP 12 can now play QuickTime (MOV) and MP4 videos. This change is especially significant because Microsoft PowerPoint, which uses the same Windows Media Player engine, now supports these formats as well.
One of the most important features of a media player, at least for the purpose of these tutorials, is its ability to display subtitles and captions. WMP 12 can display subtitles and captions when playing a DVD, but not when playing an MP4 video created from a DVD. The QuickTime Player also has trouble with MP4 video subtitles and captions. However, the VLC Player allows easy access to these features in DVD and MP4 videos.

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Multimedia
The term multimedia, as used in these tutorials, includes digital video, audio podcasts, animations created in Adobe Flash, and narrated slide shows. Multimedia also includes DVD videos. Increasingly, multimedia is moving off the desktop and into the “cloud,” so that users no longer interact with media files of any kind. For example, Prezi presentations (an alternative to PowerPoint) can be created, stored and played entirely from the Prezi website. Videos, presentation and even business computing are all moving into the cloud—a change that will result in big changes to the field of accessible multimedia.

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Screen Capture
Screen capture is the process of capturing, in video, everything that happens on a computer screen. Screen captures are commonly used for computer tutorials, where they provide viewers with a demonstration of menu selections, cursor movements, and a verbal narrative of complex computer operations. An excellent example of screen capture software is Camtasia Studio, which allows authors to record an on-screen sequence, then enhance the video in "post-production" by adding arrows, labels, pan and zoom, and more.

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Subtitles
Subtitles were developed to provide translation of foreign language dialog in film and television. They assume that the audience can hear the audio content, including music, sound effects and speaker location. In this respect, subtitles differ from captions, which were designed primarily for a non-hearing audience.
In recent years a hybrid form of alternative text has appeared: Subtitles for the Deaf and Hard of Hearing (SDH). SDH is a term introduced by the American film industry. According to Wikipedia, "SDH refers to regular subtitles in the original language where important non-dialog audio has been added, as well as speaker identification, useful when the viewer cannot otherwise visually tell who is saying what." From a user perspective, SDH subtitles are practically synonymous with captions. In fact, the captions that can be created using the techniques described in these tutorials are best described as SDH subtitles.

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Transcode
The process of converting a video from one format to another is called transcoding. In addition to changing the video container (file type), a transcoded video is frequently recompressed using a different codec. Transcoding takes place when a video from a mobile phone is saved to a DVD, and again when that DVD video is uploaded to YouTube. Transcoding involves some loss of quality—sometimes a great deal of quality—so it should be done with care and as infrequently as possible.

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Transcript
A transcript is the text equivalent of an audio recording. This "alternative text" is usable by everyone, including those with hearing and visual impairments. In addition to its use in the captioning process, a transcript may be useful in its own right as a learning tool for students, who can search for key words. Transcripts are a great addition to any instructional video or podcast because they give students another way to comprehend and interact with the material. Web video should, ideally, be accompanied by both captions and a transcript. For audio-only content, a transcript will usually suffice.
A transcript can be converted to subtitles when synchronized with a video. When contextual information (sound effects, speaker identification and location, music lyrics) is added, those subtitles become captions. Although numerous automatic transcription tools are available to convert speech to text, none provide satisfactory results at this time. The transcripts produced by automatic transcription require extensive edits and corrections. The authors therefore recommend creating transcripts manually using a word processor.

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Video Formats
Digital videos come in a variety of formats, some more common than others. No doubt you are familiar with many of the following: AVI, FLV, M4V, MOV, MP4, MPG, WMV, DV, and MPEG-2. Often a video's file extension indicates how it can be played. For example, files ending in .WMV are Windows Media Videos and play by default in the Windows Media Player. Equally common, though less obvious, are .MOV files. These are QuickTime "movies," which play in Apple's QuickTime Player and in iTunes.
While recognizing the file extension of a video may help you to play it, a deeper understanding of digital video is required if you wish to edit or create videos of your own. For example, it is important to understand that file type, such as AVI or MOV, describes only the video container; the actual contents are governed by features such as frame rate, aspect ratio and the compression/decompression algorithm (codec). Digital video is a rich and highly technical topic, and for those who are interested, much more information can be found online.

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