On-Demand Distribution of Video for Neurological Physical Exam Instruction: Attempts Using Digital Recordings and Variable Bit Rate Compression

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Conference Proceeding

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Mastery of the physical examination is a universal requirement in medical education. This exam requires performance of maneuvers and techniques that can be taught only through physical demonstration using real or simulated patients. The need for visual presentation is particularly crucial in teaching the neurological exam in which use of precise technique and observation of movement abnormalities are essential for physical diagnosis. Most neuroscience curricula routinely use real patients or videoclips to demonstrate neurologic disorders.

Use of video in day-to-day communication has increased tremendously within the last five years. Digital video capture hardware, increasingly sophisticated compression-decompression (codec) software, and high performance playback computers have made web distribution of large video files possible for many internet users. In view of the importance of visual instruction in medical education, and recent advancements in video delivery, the question before us now is how to use present technology to make this form of instruction available to students. We have investigated the potential of digital recording and advanced variable bit rate (VBR) compression schemes for use in preparing video for distribution through the internet at different bandwidths, as well as on CD-ROM. Our specific purpose has been to identify hardware and software parameters necessary to create digital source video of the neurological exam, and process it for effective on-demand delivery using existing internet transfer modes (ie., T1-LAN).

In the present project, video was recorded using a SONY DSR-200A digital video camcorder. Files were transferred via IEEE 1394 connection (FireWire) and Radius MotoDV (1.1) software from a SONY DSR-30 digital tape deck to a Power Macintosh 8600 with a Seagate Cheetah 18GB hard drive. Sorenson and Qualcomm codecs were used for video and audio, respectively, as within Media Cleaner Pro (v3.1.2). A PowerMac 9500/200 within the WSU Anatomy department was used as a server. The latest Quick Time streaming formats were tested within the WSU School of Medicine local network (T1-LAN) and at several T1-extranet sites. Data rates suitable for transfer over 56K and 28.8K dial-up modems were also tested.

Our results corroborate the general conclusions that the final video quality is directly related to the cinemagraphic quality of the source video and the processor speed of the playback machine. Specifically, at a data transfer rate of 50 KiloBytes/sec (KBS), digitally recorded and VBR compressed movies of up to 640X480 pixels in size could be delivered over T1-extranet lines with excellent movement quality when played by medium-to-high end machines (233-MHz Pentium II PC; 233-MHz Macintosh G3). Delivery at a rate suitable for 56K modems (approx 6KBS) appears promising, under ideal conditions. However, attempts to deliver video at data rates suitable for 28.8K modems (approx 3KBS) resulted in significant, and unacceptable, deterioration of movement in the video playback. The present findings suggest that on-demand distribution of video suitable for basic and clinical medical instruction is possible when appropriate source, compression, and playback parameters are used.


Presented at the 1999 Slice of Life Workshop, Philadelphia, PA.