Spatial audio coding (SAC) is a process to represent multichannel audio signals as down-mixed mono or stereo signals with spatial cues. The main strength of SAC is the significant bit-rate reduction while maintaining the perceptual sound quality. Binaural cue coding (BCC) has been introduced and now becomes an important scheme for multichannel SAC both in the sense of audio coding and the standardization issue in the MPEG. However, interchannel level difference (ICLD), one of the essential spatial cues for SAC, has a limitation that the quantized ICLD for transmission may lead to the sound quality degradation of decoded signal. In this paper, we propose virtual source location information (VSLI), which is an angle representing geometric spatial information between channels on playback layout, instead of the ICLD, and also a VSLI-based SAC system. Since a human being can not easily distinguish the variation of the spatial angle within the three degree distortion, the spatial angle, hence the VSLI, can be approximated discretely with the three degree resolution while maintaining the perceptual quality of output signals. The objective and subjective assessment results of our proposed system confirm superior performance to the ICLD-based SAC system.
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