Method and apparatus for decorrelating audio signals

DETAILED DESCRIPTION A dynamic decorrelator for surround sound signals is disclosed.
In one embodiment, a mono detection circuit is used to detect the extent to which a left rear surround input signal and a right rear surround input signal are similar.
To the extent that the surround input signals are similar, the signals are decorrelated.
Decorrelation is performed by a pair of allpass filters that introduce complementary phase shifts in the left rear surround input signal and the right rear surround input signal.
The complementary phase shifts are sufficient to prevent the surround signals from collapsing to the front of the listener when they are rendered using a pair of front speakers.
It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, a method, or a computer readable medium such as a computer readable storage medium or a computer network wherein program instructions are sent over optical or electronic communication lines.
Several inventive embodiments of the present invention are described below.
In one embodiment, a method of rendering a left rear surround input signal at a left rear virtual speaker location and rendering a right rear surround input signal at a right rear virtual speaker location is described.
The method includes phase shifting the left rear surround input signal by a first phase shift.
The right rear surround input signal is phase shifted by a second phase shift.
The phase shifted left rear surround input signal is phase shifted using an HRTF selected to render the left rear surround input signal at the left rear virtual speaker location.
The phase shifted right rear surround input signal is transformed using an HRTF selected to render the right rear surround input signal at the right rear virtual speaker location.
In another embodiment, a method of decorrelating a first input signal and a second input signal is described.
The method includes phase shifting the first input signal by a first phase shift and phase shifting second input signal by a second phase shift