Degradation Category Rating (DCR)

The second suitable method for our tool is DCR, where test sequences are presented in pairs. The first stimulus presented in each pair is always the source reference without any impairments. The second one is the same source but impaired by the test conditions. This method is also called the Double Stimulus Impairment Scale (DSIS) method. The time pattern for the stimulus presentation is depicted in Figure 4.6. The voting time should be less than or equal to 10 sec. In this case the subjects are asked to rate the impairment of the second stimulus in relation to the reference. The five-level scale for rating the impairment given in Table 4.4 is the most widely used one. However, all the quality scales used of ACR method can be used for DCR method but by replacing the quality adjectives by the corresponding impairment adjectives.