COL Documentation - COLCapture

The COL system is divided into three parts:

Class Content Capture
Administration
and Web Client.

The COL II system is based on Microsoft Windows Media Architecture. Both the production and browsing components are built on top of the Microsoft Windows Media Application Programming API.

Five types of media are captured by the COL II system: audio, video, whiteboard pen-strokes, document camera images, and the instructor's computer screen.

Audio: Three to four microphones are installed around the classroom to provide a multidimensional source of sound. The voices of the instructor and the students are captured via these microphones. The audio information is then input to the sound card of the production PC and converted to ASF format by using Microsoft Stream Technology: Windows Media Services. This ASF stream also serves as the timeline for the synchronization of all the other types of media.
Video: A video camera is mounted on the ceiling of the COL classroom. This camera produces the video stream which is then fed into the video capture card in the production PC. In general application cases, one frame per second is the least acceptable frame-rate. Because users are generally more concerned with the material on the whiteboard and the PC screen shots than the video pictures, and also because COL is based on the assumption that users will be using a 56K modem, COL only samples the video stream and produces snap-shots every five to ten seconds.
Document Camera: To avoid the confusing switch between the document camera and PC output to the LCD overhead projector, COL was designed to output the images of the document camera to the capture card in the instructor’s PC. Using the document camera is one of the PC applications. The instructor starts the document camera application program by double-clicking doccamera.exe icon on the desktop of the PC.
Whiteboard Data: Mimio, which is produced by Virtual Link, consists of a bar mounted on a regular whiteboard, and it uses a special eraser and electronic pen jackets. A regular whiteboard marker is encapsulated in an electronic pen jacket, which is only slightly larger in circumference than the marker. The jacket transmits ultra-sound signals to the bar to report the pen-down events, which enables the system to track the instructor’s pen strokes. The capture range size is around 4 feet by 8 feet. The bar receives the signal and transmits the data to the production PC through the RS-232 communication port. The specially equipped eraser works in a similar way.

COL was programmed by using the DLL file provided by Virtual Link to capture marker and eraser movements and then convert this data into the COL proprietary format. In addition to capturing the pen-strokes as vectors, COL also captures and stores the whiteboard drawings as a picture once per minute. Through that, the functionality of "forward" and "rewind" for use in browsing through the entire class session timeline was implemented.

PC Screen Shot: The instructor may use the computer in the classroom to demonstrate Web sites, a Visual Basic program, etc. In Course OnLine I, the computer screen was captured through the video camera, but the readability of the pictures on the PC screen was very limited. One of the significant improvements of the COL II system is the capture of the computer screen directly from the video memory of the instructor's PC. To do this, a program called COLAGENT, which is a daemon process running under the instructor's PC, was created. COLAGENT listens for commands from the production PC. When a "start capture" command is received, this program starts to produce screenshots. It compares the new screenshot with the last one and sends only the changes to the production PC to compress the data. When the "stop" command is received, the COLAGENT ceases.

COLCapture - System Overview