Captioned Lecture Video: Searchable, Accessible, and Archive-Friendly
by Shelley Haven
"Closed Captioned for the Hearing Impaired" - it's no wonder most people associate captioning with disabilities. But like many assistive technologies, captioning has benefits for everyone, and nowhere is this more apparent than in the academic community.
Case in point: captioned video of course lectures not only aids in comprehension of the material, but can enable students and researchers to search the lectures as they would any text-based materials. The Office of Accessible Education (OAE) has partnered with Stanford's Center for Probing the Nanoscale (CPN) on a technology demonstration project to explore the logistics and benefits of this approach.
AP275: Probing the Nanoscale (Now with Captions)
The Center for Probing the Nanoscale (CPN) is a joint venture founded by Stanford and IBM, and funded by the National Science Foundation. One of the Center's overarching goals is to educate the next generation of scientists and to inspire middle school students and their teachers through a professional development program. A cornerstone of this education component is the course Probing the Nanoscale, matriculating over 25 graduate and advanced undergraduate students. The course consists of a set of pedagogical lectures on the principles and practice of various scanning probes, followed by seminar-type lectures on research applications being pursued in the CPN. Probing the Nanoscale helps achieve tight integration between Center research and education, and the course materials will ultimately become an advanced online reference.
To ensure that course lectures impact a broad range of students, including those with disabilities, the CPN and the Office of Accessible Education are collaborating to make course materials available in a wide range of alternative formats, including captioned streaming video where transcripts of the spoken lecture appear as subtitles.
This text is synchronized with the video via a SMIL file (Synchronized Multimedia Integration Language), making it possible to search the video by means of the associated text. On the CPN video search page, users can type a word or phrase (e.g., "tunneling microscopy") to generate a table showing where the search term appeared in which lectures and the context in which it was used. Clicking the accompanying link opens the video 10 seconds prior to use of the term. (Note: these particular videos require QuickTime and the Ensharpen codec. See the search page for details.)
Captioning: It's Not Just About Disabilities!
Captioned video is an excellent example of Universal Design for Learning, or UDL. The concept of Universal Design comes from the fields of architecture and product design and is defined (by architect Ron Mace, Founder of the Center for Universal Design at North Carolina State University) as "the design of products and environments to be usable by all people, to the greatest extent possible, without the need for adaptation or specialized design." A ubiquitous example is the sidewalk curb cut, designed to meet the needs of a wide variety of users and situations (those with wheelchairs, bicycles, inline skates, baby strollers, cargo dollies, etc.). UDL, then, can be defined as an instructional environment that is accessible to, and usable by, the widest range of learners and instructional scenarios.
Captioning video makes it accessible to students with hearing impairments or deafness and facilitates compliance with various laws and guidelines (e.g., Sections 504 and 508 of the Rehabilitation Act, W3C's Web Content Accessibility Guidelines. But it also provides these benefits:
- Multimodal learning enhances comprehension. (This is especially helpful with complex topics or technical terms.)
- It is easier to understand for listeners with language barriers (i.e., instructor and learner have different native languages).
- It facilitates more flexible use. It is accessible on alternative devices (e.g., a PDA) or in less-than-ideal environments (e.g., noisy, computer with no sound card or speakers).
- It can be made searchable and index-able. This feature offers added value for all students, facilitates more effective research, and increases the "shelf life" of media (i.e., it retains value over time).
Archive-Friendly Video and Audio
Thanks to inexpensive videocams and easy-to-use software, it's fairly simple to capture video of lectures and discussions, create video-only course materials, and fulfill student assignments with podcasts. It's so simple, in fact, that more and more video-based academic material is being created, often in lieu of textual representations of the material. This creates two problems:
- The video is difficult to search. Except for keywords and metadata stored with the media, users may have to watch the entire video to discover what's there, which is very inefficient and time-consuming
- It has a reduced shelf life. Because of the difficulty in searching, the shelf life of that material can be significantly shorter, often of little value beyond the initial use for a class or project.
Searchable captioned media addresses both of these issues by making video and audio as easy to search as text documents.
Behind the Scenes
For the CPN lectures, PowerPoint slides and the lecturer's voice are captured using Camtasia. The resulting video file is sent to a streaming media server; audio is uploaded to a vendor for transcription. Until it's practical to automatically transcribe lectures with speech recognition software, this process currently involves a person in the loop. Someone types while listening to playback, a trained transcriptionist enters the data using a stenography machine, or the lecture is "revoiced" by someone trained in speech recognition who listens and dictates. (While speech recognition works excellently in a controlled dictation environment, current state-of-the-art cannot reliably handle the variables of an animated, more conversational lecture.)
The transcript is edited for accuracy, then transcript and video are synchronized with the help of specialized software (e.g., HiCaption) or through services such as Automatic Sync Technologies. The search Web page queries a search server that holds a mySQL database of every word used in the lectures and its time location. When a user submits a search term, the search Web page queries the database and returns a table showing lecture, context, and specific times when the term was used. Clicking a link tells QuickTime to access the appropriate streaming video and start playing at the desired point. See also Academic Technology Specialists Present Collaborative Projects with Faculty in this issue.
For More Information
If you have questions about this project and Universal Design, about computer accessibility and technology accommodations, or just wish to learn more about the intriguing assistive technology available, contact Shelley Haven in the Assistive Learning Technology Center (ALTeC) at 725-6173 or rmhaven@stanford.edu.
