engleski

Objective and Subjective Evaluations of Picture Quality in Digital Video Systems

A general discussion of video quality must take into consideration a variety of factors including spatial and temporal resolution and color reproducibility. In this paper the extent to which the quality of video signal is degraded by process of compression and decompression is considered. Significant compression is achievable only by lossy compression algorithms which do not permit the exact recovery of the original image. The difference between the original and decompressed image is given as reconstruction error which is the standard objective measure of picture quality. Objective measurements quantify the influence of spatial resolution and there is not possible to infer the effect of variations in temporal domain (temporal resolution). Therefore, objective measurements have limited effectiveness in predicting the quality of compressed images as seen by the observes. There is no general method known for this type of evaluation except subjective evaluation. In this paper we describe the measurement of picture quality using subjective evaluation procedure. MPEG-1 coding algorithms for video compression was applied to four difference type of video sequences with different level of movement at several bit rates to produce the test material for subjective assessment of picture quality. The results are evaluated using the mean opinion score as the measure of picture quality.

video compression algorithms; MPEG-1; reconstruction error; subjective evaluations; test sequence

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