JND-based spatial parameter quantization of multichannel audio signals

In multichannel spatial audio coding (SAC), the accurate representations of virtual sounds and the efficient compressions of spatial parameters are the key to perfect reproduction of spatial sound effects in 3D space. Just noticeable difference (JND) characteristics of human auditory system can be used to efficiently remove spatial perceptual redundancy in the quantization of spatial parameters. However, the quantization step sizes of spatial parameters in current SAC methods are not well correlated with the JND characteristics. It results in either spatial perceptual distortion or inefficient compression. A JND-based spatial parameter quantization (JSPQ) method is proposed in this paper. The quantization step sizes of spatial parameters are assigned according to JND values of azimuths in a full circle. The quantization codebook size of JSPQ was 56.7 % lower than one of the quantization codebooks of MPEG surround. Average bit rate reduction on spatial parameters for standard 5.1-channel signals reached up to approximately 13 % compared with MPEG surround, while preserving comparable subjective spatial quality.