LS on Subjective quality evaluation of AI-based ultra-low bitrate voice codecs
Source: ITU-T Study Group 12
Reference: SG12-LS18 (SG12-TD298R1)
Date: Geneva, 9-18 September 2025
For Information to: 3GPP SA4
Deadline: June 2026
ITU-T SG12 reviewed multiple contributions during its September 2025 meeting addressing ML- and AI-based speech processing features and their evaluation using subjective tests and objective models. A key contribution (SG12-C40) from Rohde & Schwarz SwissQual AG presented P.800 listening test results that included several AI-based ultra-low bitrate codecs.
The P.800 listening tests demonstrated that several AI-based ultra-low bitrate codecs scored better than traditional low-bitrate codecs, proving their usefulness in the telecommunication context.
While the P.800 overall MOS rating procedure appears generally appropriate for evaluating these codecs, SG12 identified potential limitations:
SG12 concluded that it would be premature to incorporate these AI-based codecs into the E-model (by deriving equipment impairment factors) due to:
ITU-T SG12 is seeking feedback from 3GPP SA4 based on their experience before deciding to:
The liaison includes attachment SG12-C40 describing a subjective ACR LOT testing of AI-based and ultra-low bitrate codecs in a full-scale real field context.