Quantifying Quality Degradation of the EVS Super-Wideband Speech Codec

Voice transmission networks are commonly planned with the help of computational quality models, which give an estimate of the expected quality that a user will experience. The most popular of these tools is the E-model. When certain parameters are known, such as the applied codec and its bitrate, the model is able to predict the perceived quality of a communication system. Up to now, the E-model is only available for narrowband telephony (300-3400 Hz) and limited also for wideband telephony (100-7000 Hz). With the extension of voice networks to super-wideband telephony (50-14000 Hz), and the introduction of the super-wideband codec EVS to mobile networks and state of the art smartphones, an update of the E-model has become necessary. To this end, we firstly examined the quality improvement of super-wideband over wideband with results from mixed-band listening-only tests, where we found that the quality is improved by 15%. Then, we calculated impairment factors for the EVS codec and analyzed its robustness towards packet loss, by using auditory and instrumental methods.