Quality assessment for extending ITU-T G.729 annexes

Since ITU-T Recommendation G.729 for an 8 kbit/s speech coding scheme and its Annexes A, B, C, D, and E were adopted, they have become widely used for wireless and other applications. Also, in response to market demands for more flexible variable-rate operation, improved adaptability to packetization, and implementation of a software encoder, ITU-T recommended new Annexes that added a silence compression function and bit rate switching to existing Annexes and floating-point implementations of existing Annexes. The authors clarified the quality requirements required for verifying both the quality of a new Annex that was created by adding a new function to an existing Annex and its compatibility with the existing Annex, selected the quality assessment technique (assessment items and assessment method) required for deciding whether to accept or reject the proposal for the new Annex, and reflected that technique in the recommendation procedure in the ITU-T. They followed that procedure to assess the quality of the new Annex proposals and verified that the quality was sufficient for a Recommendation. In this paper, the authors describe the circumstances in which Annexes F, G, H, I, and C+ were recommended as new Annexes of G.729, the quality assessment technique for requirements that were determined by taking into consideration the application areas, an examination of the subjective quality assessment tests that were conducted when the Annexes were recommended, and the assessment results.