Rohde & Schwarz: EVS AMR-WB IO improves telephone service speech quality
Rohde & Schwarz has investigated improvements in telephone service speech quality using the Enhanced Voice Services (EVS) AMR-WB interoperable (IO) mode. The study focuses on the compatibility of the newer EVS codec with the legacy AMR-WB codec.
German electronics company Rohde & Schwarz has released findings from a study on speech quality improvements in telephone services utilizing the Enhanced Voice Services (EVS) AMR-WB interoperable (IO) mode. This mode ensures compatibility with older AMR-WB codecs in mobile networks.
The EVS codec, introduced in 2014 by 3GPP, was designed to replace AMR-WB for VoLTE and VoNR services. It enhances speech quality through improved coding, a wider audio bandwidth up to 20kHz, and better compensation for delay jitter and packet loss. The EVS AMR-WB IO mode allows for encoding and decoding of AMR-WB streams, maintaining compatibility with systems that do not support EVS.
An internal study by Rohde & Schwarz compared the performance of the EVS AMR-WB IO encoder against the traditional AMR-WB encoder. Listening tests indicated that the EVS AMR-WB IO decoder could produce superior speech quality from an AMR-WB encoded bitstream compared to a standard AMR-WB decoder.
The tests were conducted at Rohde & Schwarz's SwissQual speech quality lab in Switzerland. Participants evaluated speech quality on a five-point scale. The results suggest that using the EVS AMR-WB IO mode enhances perceived speech quality over the legacy AMR-WB codec, particularly under less optimal network conditions.