Dual-Mode AVQ Coding Based on Spectral Masking and Sparseness Detection for ITU-T G.711.1/G.722 Super-Wideband Extensions

ITU-T Recommendations G.711.1 Annex D and G.722 Annex B, which are super-wideband (50–14,000 Hz) extensions to G.711.1 and G.722, have been recently standardized. This paper introduces a new coding method proposed and employed in the above ITU-T standards. The proposed coding method employs an adaptive spectral masking of the algebraic vector quantization (AVQ) for MDCT-domain non-sparse signals. The adaptive spectral masking is switched on and off based on MDCT-domain sparseness analysis. When the target MDCT coefficients are categorized as non-sparse, masking level of the target MDCT coefficients is adaptively controlled using spectral envelope information. The performance of the proposed method as a part of the ITU-T G.711.1 Annex D is evaluated in comparison with the ordinary AVQ. Subjective listening test results show that the proposed method improves the sound quality more than 0.1 points with a five grade scale in average of speech, music and mixed content, and the significance of the improvement is validated.