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June 29, 2011

Stanford's video processing in the cloud allows interactive streaming of online lectures

Stanford researchers designed software that allows a viewer to zoom and pan while streaming online courses. They recently released the code to the public.

By Melissae Fellet

Postdoctoral student Ngai-Man Cheung and graduate students Sherif Halawa and Derek Pang are writing algorithms for Stanford's ClassX project. (Photo by Linda A. Cicero)

Stanford researchers have publicly released the program code for software they first created to convert static videos of class lectures into interactive online video streams.

Typically, recording college courses requires a specially designed lecture hall outfitted with remotely controlled cameras. A person operates the cameras from a control room, zooming closer as the speaker writes on the board or panning as she walks across the room.

The Stanford Center for Professional Development operates nine of these specially designed classrooms to record engineering courses for technology industry professionals. They've posted these videos online since 1996.

But the technology is expensive. Electrical engineering professor Bernd Girod estimates one of these classrooms costs more than $100,000.

"Our students thought about technological advances, took initiative and said, 'We can do the same thing for $500,'" he said.

Girod and his students simplified the recording equipment to three items: a tripod, a wireless microphone and a high-definition camcorder. Then they designed software that processes the video so the viewer can zoom and pan around the room during playback. Alternatively, the program can control the view automatically.

From lecture to streaming video, humans only intervene to set up the camcorder and upload the video file to a remote server accessed online. Since the program works in the cloud, users only need a web browser to access the interactive video.

Girod and his students launched their ClassX platform in September 2009. The team released the program code as open-source software in early April.

The website currently houses 25 courses, as well as numerous seminars and workshops. The system has been used to record courses large and small, from an advanced electrical engineering class with 15 students to a large introductory biochemistry lecture with more than 200 students. Chalkboard lectures, projected slides and chemistry demonstrations all display clearly.

The software divides the original video into rectangular "tiles" and considers each tile its own video stream. The server stores the tiles in a variety of resolutions, from a wide view at the back of the room to close-up shots. To reduce the amount of information sent while streaming, the program transmits only those tiles that a viewer requests. When a user zooms in, the server delivers the close-up stream.

The ClassX interface pairs the lecture video with slides from a computer presentation. The program automatically analyzes the video using advanced computer vision algorithms and synchronizes the slides with the video, advancing the displayed slide when it changes in the video. Slide synchronization also makes it extremely easy to jump to a specific topic within the lecture, which can be tedious when searching through a single 75-minute video.

The courses remain archived on the web. Lecturers can choose to make them accessible to members of the Stanford community or the public.

Graduate student Derek Pang is one of the students developing ClassX Mobile, an extension of the platform for tablet computers and smartphones. For now, the system is still experimental. The software must handle the unpredictable connectivity of wireless networks, perform without reducing battery life and work with the limited computing power of mobile devices.

"In the future, I fully expect to see students riding their bikes across campus watching lectures and making pinching gestures with their fingers to zoom in," Girod said with a laugh.

Until recently, ClassX was a side project for students – a "labor of love," Girod said. ClassX Mobile was developed as part of the Stanford-based Programmable Open Mobile Internet 2020 research center funded by the National Science Foundation. Now the Stanford President's Office has allocated funds that will allow the team to hire a web developer for a project that unifies three complementary online education platforms on campus: ClassX, CourseWare and Open Classroom.

Graduate student Sherif Halawa said there's good demand for ClassX.

"Many professors use it once and then come back wanting to use it in future courses. They recommend it to others, too," he said.

When ClassX first launched, two classes used it each quarter, Halawa said. This spring, the team hosted nine courses.

The Stanford Center for Professional Development currently offers 50 to 60 recorded courses each quarter. That puts the high-tech videotaping rooms in great demand. "Scheduling is a big challenge," said Joyce Rice, the center's director of marketing.

ClassX provides an alternative recording method when the center can't cover a course, Pang said. With basic video equipment and storage space on a computer server, any classroom can become a place for online instruction.

Melissae Fellet is a science-writing intern at the Stanford News Office. 




ClassXTeam, Department of Electrical Engineering:

Dan Stober, Stanford News Service: (650) 721-6965,

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