IN{SERVICE IMAGE MONITORING USING PERCEPTUAL OBJECTIVE QUALITY METRICS
Tubagus Maulana Kusuma · 2003
User-oriented image quality assessment has become a key factor in multimedia communications as a means of monitoring perceptual service quality. However, existing image quality metrics such as Peak Signal-to-Noise Ratio (PSNR) are inappro- priate for in-service quality monitoring since they require the original image to be available at the receiver. Although PSNR and others are objective metrics, they are not based on human visual perception and are typically designed to measure the delit y. On the other hand, the human visual system (HVS) is more sensitive to perceptual quality than delit y. In order to overcome these problems, we propose a novel objective reduced-reference hybrid image quality metric (RR-HIQM) that accounts for the human visual perception and does not require a reference image at the receiver. This metric is based on a combined approach of various but specic image artifact measures. The result is a single number, which represents an overall image quality. Transmission of multimedia services such as image and video over a wireless communication link can be expected to grow rapidly with the deployment of third and future generation mobile radio systems (1). These mobile radio systems also aim at oering higher data rates, improved reliability and spectrum eciency . This will allow for a va- riety of wireless multimedia services to be delivered over a hostile radio channel while maintaining satisfactory ser- vice quality. However, experiments have shown that the conventional quality measures, such as Bit Error Rate (BER) or Frame Error Rate (FER) are not adequate for quality assessment related to image and video transmis- sion. For example, the eects of only a few bit errors or even a single bit error in the source-compressed im- age or video stream can propagate through a substantial portion of the decompressed data and may cause a se- vere degradation in the user-perceived quality. Therefore, user oriented quality metrics that incorporate human vi- sual perception have become of great interest in image and video delivery services (2,3). Although the best and truest judge of quality is human through subjective tests, continuous monitoring of communication systems qual- ity by subjective methods is tedious, expensive and not practical in a real-time environment. Therefore, objective quality measurement methods which closely approximate the subjective test results are sought after. Another incentive for the search after user oriented quality metrics is the fact that the commonly used im- age delit y and quality metrics like Mean-Squared Error (MSE) and Peak Signal-to-Noise Ratio (PSNR) are in- appropriate for in-service quality monitoring because the reference image is unavailable at the receiver. These ex- isting metrics fall into the category of full-reference (FR) metrics (3). In order to overcome this problem, the pro- posed novel reduced-reference (RR) objective perceptual image quality metric does not require a reference image and is based on the human visual system (HVS).