US 5,890,125 A · Method and apparatus for encoding and decoding multiple audio channels at low bit rates using adaptive selection of encoding method

Abstract

A split-band coding system combines multiple channels of input signals into various forms of composite signals and generates spatial-characteristic signals representing soundfield spatial characteristics in a plurality of frequency subbands. The spatial-characteristics signals may be generated in either or both of two forms. In a first form, the signal represents measures of signal levels for subband signals from the input channels. In a second form, the signal represents one or more apparent directions for the soundfield. The type of the spatial-characteristics signal may be adapted dynamically in response to a variety of criteria including input signal characteristics. Temporal smoothing and spectral smoothing of the spatial-characteristics signals may be applied in an encoder. Temporal smoothing and spectral smoothing may be applied to gain factors derived from the spatial-characteristics signals in a decoder.

Claims69

Dependent claims

A method for generating an encoded signal by encoding a plurality of input signals each representing a respective channel of audio information, said method comprising:

generating a plurality of channel subband signals representing said input signals in a plurality of frequency subbands,
generating a composite signal representing at least a portion of the bandwidth of said input signals,
generating a spatial-characteristic signal representing spatial characteristics of a soundfield associated with said composite signal in response to respective channel subband signals in a frequency subband, wherein said spatial-characteristic signal is generated in either or both of a first form conveying information representing signal levels of said respective channel subband signals and a second form representing one or more intended directions, wherein the forms in which to generate said spatial-characteristics signal are determined adaptively, and
assembling said composite signal, said spatial-characteristics signal and an indication of the form of said spatial-characteristics signal into said encoded signal.

1 more element

A method for decoding an encoded signal to generate one or more output signals for presentation via one or more output transducers, said method comprising:

obtaining from said encoded signal one or more composite signals, a plurality of spatial-characteristics signals and an indication of the form of said spatial-characteristics signals, and deriving a plurality of composite subband signals from said one or more composite signals, wherein each spatial-characteristics signal is associated with a respective composite subband signal and represents spatial characteristics of a respective soundfield corresponding to said respective composite subband signal, wherein said indication indicates whether said spatial-characteristics signals are in a first form representing a plurality of signal levels and/or are in a second form representing one or more directions,
deriving from said spatial-characteristics signals a plurality of gain factors and mapping a respective composite subband signal into one or more interim subband signals according to a respective gain factor wherein, for said associated spatial-characteristic signal having said first form, said mapping is also according to a spatial configuration signal associated with said signal levels and a transducer configuration signal representing a spatial configuration of said output transducers, and wherein, for said associated spatial-characteristic signal having said second form, said mapping is also according to said one or more directions and said transducer configuration signal, and
generating said plurality of output signals by applying one or more inverse filter banks to said interim subband signals.

A medium readable by a machine, embodying a program of instructions executable by said machine to perform a method for generating an encoded signal by encoding a plurality of input signals each representing a respective channel of audio information, said method comprising:

generating a plurality of channel subband signals representing said input signals in a plurality of frequency subbands,
generating a composite signal representing at least a portion of the bandwidth of said input signals,
generating a spatial-characteristic signal representing spatial characteristics of a soundfield associated with said composite signal in response to respective channel subband signals in a frequency subband, wherein said spatial-characteristic signal is generated in either or both of a first form conveying information representing signal levels of said respective channel subband signals and in a second form representing one or more intended directions, wherein the forms in which to generate said spatial-characteristics signal are determined adaptively, and
assembling said composite signal, said spatial-characteristics signal and an indication of the form of said spatial-characteristics signal into said encoded signal.

1 more element

A medium readable by a machine, embodying a program of instructions executable by said machine to perform a method for decoding an encoded signal to generate one or more output signals for presentation via one or more output transducers, said method comprising:

obtaining from said encoded signal one or more composite signals, a plurality of spatial-characteristics signals and an indication of the form of said spatial-characteristics signals, and deriving a plurality of composite subband signals from said one or more composite signals, wherein each spatial-characteristics signal is associated with a respective composite subband signal and represents spatial characteristics of a respective soundfield corresponding to said respective composite subband signal, wherein said indication indicates whether said spatial-characteristics signals are in a first form representing a plurality of signal levels and/or are in a second form representing one or more directions,
deriving from said spatial-characteristics signals a plurality of gain factors and mapping a respective composite subband signal into one or more interim subband signals according to a respective gain factor wherein, for said associated spatial-characteristic signal having said first form, said mapping is also according to a spatial configuration signal associated with said signal levels and a transducer configuration signal representing a spatial configuration of said output transducers, and wherein, for said associated spatial-characteristic signal having said second form, said mapping is also according to said one or more directions and said transducer configuration signal, and
generating said plurality of output signals by applying one or more inverse filter banks to said interim subband signals.

An encoder for generating an encoded signal by encoding a plurality of input signals each representing a respective channel of audio information, said encoder comprising:

means for generating a plurality of channel subband signals representing said input signals in a plurality of frequency subbands,
means for generating a composite signal representing at least a portion of the bandwidth of said input signals,
means for generating a spatial-characteristic signal representing spatial characteristics of a soundfield associated with said composite signal in response to respective channel subband signals in a frequency subband, wherein said spatial-characteristic signal is generated in either or both of a first form conveying information representing signal levels of said respective channel subband signals and in a second form representing one or more intended directions, wherein the forms in which to generate said spatial-characteristics signal are determined adaptively, and
means for assembling said composite signal, said spatial-characteristics signal and an indication of the form of said spatial-characteristics signal into said encoded signal.

1 more element

A decoder for decoding an encoded signal to generate one or more output signals for presentation via one or more output transducers, said decoder comprising:

means for obtaining from said encoded signal one or more composite signals, a plurality of spatial-characteristics signals and an indication of the form of said spatial-characteristics signals, and for deriving a plurality of composite subband signals from said one or more composite signals, wherein each spatial-characteristics signal is associated with a respective composite subband signal and represents spatial characteristics of a respective soundfield corresponding to said respective composite subband signal, wherein said indication indicates whether said spatial-characteristics signals are in a first form representing a plurality of signal levels and/or are in a second form representing one or more directions,
means for deriving from said spatial-characteristics signals a plurality of gain factors and for mapping a respective composite subband signal into one or more interim subband signals according to a respective gain factor wherein, for said associated spatial-characteristic signal having said first form, said mapping is also according to a spatial configuration signal associated with said signal levels and a transducer configuration signal representing a spatial configuration of said output transducers, and wherein, for said associated spatial-characteristic signal having said second form, said mapping is also according to said one or more directions and said transducer configuration signal, and
means for generating said plurality of output signals by applying one or more inverse filter banks to said interim subband signals.

Dependencies are inferred from the claim text.

Method and apparatus for encoding and decoding multiple audio channels at low bit rates using adaptive selection of encoding method

Life of this patent

Method and apparatus for encoding and decoding multiple audio channels at low bit rates using adaptive selection of encoding method

Life of this patent

Abstract

Claims69