Conventional parametric stereo (PS) audio coding employs inter-channel phase difference and overall phase\r\ndifference as phase parameters. In this article, it is shown that those parameters cannot correctly represent the phase\r\nrelationship between the stereo channels when inter-channel correlation (ICC) is less than one, which is common in\r\npractical situations. To solve this problem, we introduce new phase parameters, channel phase differences (CPDs),\r\ndefined as the phase differences between the mono downmix and the stereo channels. Since CPDs have a descriptive\r\nrelationship with ICC as well as inter-channel intensity difference, they are more relevant to represent the phase\r\ndifference between the channels in practical situations. We also propose methods of synthesizing CPDs at the\r\ndecoder. Through computer simulations and subjective listening tests, it is confirmed that the proposed methods\r\nproduce significantly lower phase errors than conventional PS, and it can noticeably improve sound quality for stereo\r\ninputs with low ICCs.
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