Techniques for Assessing the Visual Quality of Digitized Imagery

A methodology for assessing the visual quality of digitized imagery and video will be developed. Loss of image quality is noticed after an image has been compressed and reconstructed using JPEG, wavelet or fractal compression techniques. Test by IAs and formal subjective tests (e.g., CCIR 500) can provide reliable, relative measures of video quality. However, such testing is time-consuming and expensive. Objective testing methods are needed to provide efficient, repeatable measures of video quality, and greater insights into the nature of impairments. Presently, no standardized objective measures exist for digital video. However, pioneering work has been done by NTIA, NASA, ACATS and others to quantify the quality of digital imagery and video. Codec manufacturers have implemented some of the published measurements and others of their own design. These measures utilize complex digital image processing techniques to analyze differences between source and processed video sequences. The methodologies found in Phase I will be implemented for automation in Phase II using an inexpensive PC-based system. The initial product will be a PC-based turnkey system for measuring the objective picture quality of digital imagery compression systems. The computer will control a video tape player such as a Betacam SP machine, play test material from a tape recorder through the codec and capture it. It will then make comparisons of the source material and the codec processed material. The system will be bundled with a codec test tape containing standard video test materials appropriate for a variety of customers. Alternatively, the system can measure quality for user-supplied test materials. Measurements include ANSI draft standard measurements, PSNR and Impairment Quality Rating (CCIR-500 scale) for any imagery or video sequences. Techniques for ascertaining the quality of digitized imagery and video will improve the capability of digitization and compression systems. Commercial applications include products that test digital video and image compression systems. The products will be developed by software integration of COTS hardware. It is intended for use by most of the major telecommunications compan