Patent ID: 9628934
Date: 2017-04-18
CPC Classifications: H04S

Claim:
1. A process for upmixing N audio input channels, each associated with a spatial direction, to M audio output channels, each associated with a spatial direction, wherein M and N are positive whole integers and M is greater than N, comprising deriving said M audio output channels from said N audio input channels, wherein at least one of said one or more of said M audio output channels being derived from a respective set of at least three of said N input channels, at least one of said one or more of said M audio output channels is derived from a respective set of at least three of said N input channels at least in part by approximating the cross-correlation of said at least three of said N input channels, the value of cross-correlation having a set lower limit; determining if there is low pair-wise correlation among any of the N audio input channels or if there is low signal level at any of the N audio input channels such that at least some of the M audio output channels gets zero or significantly low signal; providing an augmented upmix mode in which the N input channel signals are augmented so that at least some signal output is provided in each of the M audio output channels if the at least some of the M audio output channels gets zero or significantly low signal, wherein the augmented upmix of channels is performed by setting the lower limit on the value of the cross correlation and taking a weighted average of the signal power of the input channels from which the M audio output channels are derived, and which produces some signal in the M audio output channels even in signal conditions where the at least some M audio output channels would be zero due to the low pair-wise correlation or significantly low signal levels of any of said input channels from which the M audio output channels are derived; setting a lower limit than a previous limit indicating correlation on a value of the cross correlation for the each pair, wherein the lower limit comprises the minimum value of the cross-correlation and is based on a random equal-distribution correlation value; and taking the weighted average of the signal power of the input channels relative to the lower limit to assure that the at least some signal is provided in the each M audio channels.