Comparison of the Methods

An important issue in choosing a test method is the fundamental difference between methods that use explicit references (e.g. DCR or DSCQS) and methods that do not use any explicit reference (e.g. ACR). The latter does not test fidelity. The former, on the other hand, should be used when testing the fidelity of transmission with respect to the source signal. Thus, when it is important to check the fidelity with respect to the source signal, the DCR method should be used. Discrimination of imperceptible/perceptible impairment in the DCR scale supports this, as well as comparison with the reference quality. DSCQS, in addition, is used in the cases when the quality range is not completely covered. On the other hand, ACR is easy and fast to implement and the presentation of the stimuli is similar to that of the common use of the systems. Thus, ACR is well suited for qualification tests.

Figure 4.7: A portion of quality rating form using continuous scales.

  

Figure 4.8: A portion of quality rating form using continuous scales for DSCQS method.