Reconstructing Audio Signals With Multiple Decorrelation Techniques and Differentially Coded Parameters

An audio decoder for decoding M encoded audio channels representing N audio channels, the audio decoder comprising:

• an input interface for receiving a bitstream containing the M encoded audio channels and a set of spatial parameters, wherein the set of spatial parameters includes an amplitude parameter, a correlation parameter, and a phase parameter, wherein the amplitude parameter is differentially encoded across frequency;
• an audio decoder for decoding the M encoded audio channels, wherein each audio channel is divided into a plurality of frequency bands, and each frequency band includes one or more spectral components;
• a demultiplexer for extracting the set of spatial parameters from the bitstream;
• a processor for applying a differential decoding process across frequency to the differentially encoded amplitude parameter to obtain a differentially decoded amplitude parameter, and analyzing the M audio channels to detect a location of a transient and analyzing the M audio channels to detect a location of a transient;
• a decorrelator for decorrelating the M audio channels, wherein a first decorrelation technique is applied to a first subset of the plurality of frequency bands of each audio channel and a second decorrelation technique is applied to a second subset of the plurality of frequency bands of each audio channel;
• a reconstructor for deriving N audio channels from the M audio channels and the set of spatial parameters, wherein N is two or more, M is one or more, and M is less than N;
• and
• an audio reproduction device that synthesizes the N audio channels as an output audio signal,
• wherein both the analyzing and the decorrelating are performed in a frequency domain, the first decorrelation technique represents a first mode of operation of a decorrelator, and the second decorrelation technique represents a second mode of operation of the decorrelator.

A method performed in an audio decoder for reconstructing N audio channels from an audio signal having M audio channels, the method comprising:

• receiving a bitstream containing the M audio channels and a set of spatial parameters, wherein the set of spatial parameters includes an amplitude parameter and a correlation parameter;
• decoding the M encoded audio channels, wherein each audio channel is divided into a plurality of frequency bands, and each frequency band includes one or more spectral components;
• extracting the set of spatial parameters from the bitstream;
• analyzing the M audio channels to detect a location of a transient, wherein the location of the transient is detected based on a filtering operation;
• decorrelating the M audio channels to obtain a decorrelated version of the M audio channels, wherein a first decorrelation technique is applied to a first subset of the plurality of frequency bands of each audio channel and a second decorrelation technique is applied to a second subset of the plurality of frequency bands of each audio channel;
• deriving N audio channels from the M audio channels, the decorrelated version of the M audio channels, and the set of spatial parameters, wherein N is two or more, M is one or more, and M is less than N;
• and
• synthesizing, by an audio reproduction device, the N audio channels as an output audio signal,
• wherein both the analyzing and the decorrelating are performed in a frequency domain, the first decorrelation technique represents a first mode of operation of a decorrelator, the second decorrelation technique represents a second mode of operation of the decorrelator, and the audio decoder is implemented at least in part in hardware.

An audio decoder for decoding M encoded audio channels representing N audio channels, the audio decoder comprising:

• an input interface for receiving a bitstream containing the M encoded audio channels and a set of spatial parameters, wherein the set of spatial parameters includes an amplitude parameter and a correlation parameter;
• an audio decoder for decoding the M encoded audio channels, wherein each audio channel is divided into a plurality of frequency bands, and each frequency band includes one or more spectral components;
• a demultiplexer for extracting the set of spatial parameters from the bitstream;
• a processor for analyzing the M audio channels to detect a location of a transient, wherein the location of the transient is detected based on a filtering operation;
• a decorrelator for decorrelating the M audio channels, wherein a first decorrelation technique is applied to a first subset of the plurality of frequency bands of each audio channel and a second decorrelation technique is applied to a second subset of the plurality of frequency bands of each audio channel;
• a reconstructor for deriving N audio channels from the M audio channels and the set of spatial parameters, wherein N is two or more, M is one or more, and M is less than N;
• and
• an audio reproduction device that synthesizes the N audio channels as an output audio signal,
• wherein both the analyzing and the decorrelating are performed in a frequency domain, the first decorrelation technique represents a first mode of operation of a decorrelator, and the second decorrelation technique represents a second mode of operation of the decorrelator.