Video Framerate, Resolution and Grayscale Tradeoffs for Undersea Telemanipulator Control

Abstract

Summary form only given. The high costs associated with a human diver working at ocean depths greater than 100m makes the use of remotely controlled visual inspection and manipulation attractive. However, long coaxial cables from the surface to the remote teleoperator cause additional difficulties. Therefore, sound communication without a tether is desirable. This form of telemetry, however, poses severe bandwidth restrictions so that its use for image transmission is in question. The product of Frame Rate (F) in frames per second, Resolution (R) in total pixels and grayscale in bits (G) equals the transmission baud rate in bits per second. Thus for a fixed channel capacity there are tradeoffs between F, R and G in the actual sampling of the picture for a particular manual control task in the present case remote undersea manipulation. A manipulator was used in the MASTER/SLAVE mode to study these tradeoffs. Images were systematically degreaded from 28 frames per second, 128 × 128 pizels and 16 levels (4 bits) grayscale, with various FRG combinations constructed from a real-time digitized (charge- injection) video camera. When subjects first saw the video pictures with which they had to perform remote manipulation tasks, they refused to believe that they could succeed. Much to their surprise, however, they discovered that they were able to perform with a considerably degraded picture. It was found that frame rate, resolution and grayscale could be independently reduced without…