Quality assessment of two fullband audio codecs supporting real-time communication

Abstract

Recent audio codecs enable high quality signals up to fullband (20 kHz) which is usually associated with the maximal audible bandwidth. Following previous studies on speech coding assessment, we survey in this novel study the music coding ability of two real-time codecs with fullband capability – the IETF standardized Opus codec as well as the 3GPP specified EVS codec. We tested both codecs with vocal, instrumental and mixed music signals. For evaluation, we predicted human assessments using the instrumental POLQA method which has been primarily designed for speech assessment. Additionally, we performed two listening tests as a reference with a total of 21 young adults. Opus and EVS show a similar music coding performance. The quality assessment mainly depends on the specific music characteristics and on the tested bitrates from 16.4 to 64 kbit/s. The POLQA measure and the listening results are correlating, whereas the absolute ratings of the young listeners achieve much lower MOS values.