Time-Varying Filters for Generating Decorrelation Signals

A method, comprising:

• receiving audio data corresponding to a plurality of audio channels;
• determining audio characteristics of the received audio data, the audio characteristics comprising at least one of tonality information or transient information;
• determining decorrelation filter parameters for the audio data based, at least in part, on the audio characteristics of the received audio data;
• forming a decorrelation filter according to the decorrelation filter parameters;
• and
• applying the formed decorrelation filter to at least some of the audio data,
• wherein the decorrelation filter comprises an all-pass filter;
• the decorrelation filter parameters comprise dithering parameters for movement of at least one pole of the all-pass filter, or randomly selected pole locations for at least one pole of the all-pass filter, the dithering parameters or pole locations being bounded by constraint areas within which pole movements are constrained;
• the dithering parameters or pole locations comprise a maximum stride value for pole movement corresponding to a maximum pole displacement from the most recent pole location;
• and
• the maximum stride value is based, at least in part, on the tonality information and/or the transient information.

An apparatus, comprising:

• an interface;
• and
• a logic system configured for:
• receiving, from the interface, audio data corresponding to a plurality of audio channels;
• determining audio characteristics of the received audio data, the audio characteristics comprising at least one of tonality information or transient information;
• determining decorrelation filter parameters for the audio data based, at least in part, on the audio characteristics of the received audio data;
• forming a decorrelation filter according to the decorrelation filter parameters;
• and
• applying the formed decorrelation filter to at least some of the audio data,
• wherein the decorrelation filter comprises an all-pass filter;
• the decorrelation filter parameters comprise dithering parameters for movement of at least one pole of the all-pass filter, or randomly selected pole locations for at least one pole of the all-pass filter, the dithering parameters or pole locations being bounded by constraint areas within which pole movements are constrained;
• the dithering parameters or pole locations are determined with reference to a maximum stride value for pole movement corresponding to a maximum pole displacement from the most recent pole location;
• and
• the maximum stride value is based, at least in part, on the tonality information and/or the transient information.

A method, comprising:

• receiving audio data corresponding to a plurality of audio channels;
• determining decorrelation filter control information corresponding to a maximum pole displacement of a decorrelation filter, wherein the maximum pole displacement is a maximum pole displacement from a most recent pole location;
• determining decorrelation filter parameters for the audio data based, at least in part, on the decorrelation filter control information;
• forming the decorrelation filter according to the decorrelation filter parameters;
• and
• applying the decorrelation filter to at least some of the audio data,
• wherein determining the decorrelation filter control information comprises:
• determining audio characteristic information;
• and
• determining the maximum pole displacement based, at least in part, on the audio characteristic information.