ITU definitions: subjective assessment: the determination of the quality or impairment of programme-like pictures presented to a panel of human assessors in viewing sessions(人类观测小组对节目类图片的质量或者损害进行的判断。) objective perceptual measurement: the measurement of the performance of a programme chain by the use of programme-like pictures and objective(instrumetal) measurement methods to obtain an indication that approximates the rating that would be obtained from a subjective assessment test.(通过对节目的图片使用客观测量的方法,对整个节目链进行测量,以获得一个近似于从主观评估测试中获取的评分的指标。)