4 Quality under error conditions (A-law, IRS), Experiment 1
3GPP46.008Half rate speechPerformance Characterization of the GSM Half Rate speech codecRelease 17TS
A listening-only test was chosen, adopting the Absolute Category Rating (ACR) method.
Subjective tests were carried out by BT (United Kingdom), CSELT (Italy), and Deutsche Telekom (Germany). Table 1 reports the results obtained in Experiment 1: each cell shows the difference in terms of equivalent Q values between the candidate and the full rate, negative values meaning worse performance than the full rate.
Table 1: Results from experiment 1 (A-law, IRS)
|
Input Level |
|||
|
Error Pattern |
-12 |
-22 |
-32 |
|
EP0 |
-0,27 |
-0,02 |
0,34 |
|
EP1 |
-0,26 |
-0,86 |
-0,59 |
|
EP2 |
-0,49 |
-1,61 |
1,14 |
|
EP3 |
-0,39 |
1,79 |
3,80 |
NOTE: The figures in table 1 indicate DQ values in dB, where DQ = QHR – QFR.
In general, the candidate codec performed equally well or slightly worse than the full rate (in any case never exceeded the -3 dB limit).