ENCODER

• US 20100305727A1
• Filed: 11/27/2007
• Published: 12/02/2010
• Est. Priority Date: 11/27/2007
• Status: Active Grant

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Ojanpera, Juha Petteri
• Granted Patent: US 8,548,615 B2
• Time in Patent Office: Days
• US Class Current: 700/94
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing

Abstract

An encoder for encoding an audio signal comprising at least two channels, the encoder configured to generate an encoded signal comprising at least a first part, a second part and a third part, wherein the encoder is further configured to: generate the first part of the encoded signal dependent on at least one combination of first and second channels of the at least two channels; generate the second part of the encoded signal dependent on at least one difference between the first and second channels of the at least two channels; and generate the third part of the encoded signal dependent on at least one energy ratio of the first and second channels of the at least two channels.

Claims

1-50. -50. (canceled)

51. An apparatus comprising at least one processor and at least one memory including computer program code the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

generate an encoded signal comprising at least a first part, a second part and a third part, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to;

generate the first part of the encoded signal dependent on a received time domain representation of the audio signal and on at least one combination of first and second channels of the at least two channels, wherein each of the at least one combination of the first and second channels comprises an average of at least one time domain sample from the first channel and an associated at least one time domain sample from the second channel;

generate the second part of the encoded signal dependent on at least one difference between the first and second channels of the at least two channels; and

generate the third part of the encoded signal dependent on at least one energy ratio of the first and second channels of the at least two channels.

52. The apparatus as claimed in claim 51, wherein the first part of the encoded signal is a time domain encoded signal.

53. The apparatus as claimed in claim 51 wherein the first part of the encoded signal is generated by at least one of:

advanced audio coding (AAC);

MPEG-1 layer 3 (MP3),

ITU-T embedded variable rate (EV-VBR) speech coding base line coding;

adaptive multi rate-wide band (AMR-WB) coding; and

adaptive multi rate wide band plus (AMR-WB+) coding.

54. The apparatus as claimed in claim 51 to wherein the first and second channels of the at least two channels are time domain representations, and wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to:

generate a first and second frequency domain representation of the first and second channels, wherein each of the first and second frequency domain representations of the first and second channels comprise at least two spectral coefficient values, and wherein the second part of the encoded signal comprises at least two difference values wherein each difference value is dependent on the difference between a first channel spectral coefficient value and an associated second channel spectral coefficient value.

55. The apparatus as claimed in claim 54, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to:

generate the first and second frequency domain representations of the first and second channels by transforming the time domain representations of the first and second channels, wherein transforming comprises one of;

a shifted discrete fourier transform;

a modified discrete cosine transform; and

a discrete unitary transform.

56. The apparatus as claimed in claim 54, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to group the at least two spectral coefficient values from each of the first and second frequency domain representations of the first and second channels into at least two sub-bands, each channel sub-band comprising at least one spectral coefficient value.

57. The apparatus as claimed in claim 56, wherein the third part of the encoded signal comprises at least two energy ratios, wherein each energy ratio is associated with a sub-band, wherein the encoder is configured to generate each energy ratio by determining the ratio, for each associated sub-band, of the maximum of the first and the second channels energies and the minimum of the first and the second channels energies.

58. An apparatus comprising at least one processor and at least one memory including computer program code the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to:

for decoding an encoded signal configured to;

divide the encoded signal received for a first time period into at least a first part, a second part and a third part, wherein the first, second and third parts represent an encoded first and second channels of a multichannel audio signal;

generate a first decoded signal dependent on the first part; and

generate at least one further decoded signal dependent on the first decoded signal, and at least one of the second and third parts of the encoded signal.

59. The apparatus for decoding an encoded signal as claimed in claim 58, wherein each of the at least one further decoded signals comprise at least two portions, and wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to:

determine at least one characteristic of the encoded signal associated with at least one portion of the at least one further decoded signal;

select one of the second or third parts of the encoded signal dependent on the characteristic associated with the at least one portion of the at least one further decoded signal; and

generate the at least one part of the at least one further decoded signal dependent on the first decoded signal and the selected one of the second or third parts.

60. The apparatus as claimed in claim 59, wherein the characteristic comprises at least one of:

an auditory gain greater than a threshold value;

an auditory scene being wholly located in at least one of the encoded first and second channels; and

the second part not being null.

61. The apparatus as claimed in claim 58, wherein the first decoded signal comprises at least one combined channel frequency domain representation, and wherein each combined channel frequency domain representation comprises at least two combined channel spectral coefficient portions, each combined channel spectral portion comprising at least one spectral coefficient value.

62. The apparatus as claimed in claim 58, wherein the second part of the encoded signal comprises at least one side channel value, and wherein each side channel value is dependent on a difference between a first channel spectral coefficient value and the second encoded channel spectral coefficient value.

63. The apparatus as claimed in claim 58 wherein the third part of the encoded signal comprises at least one intensity side channel encoded value, and wherein each intensity side channel encoded value comprises an encoded energy ratio between the maximum of a portion of the first encoded channel spectral coefficients and a portion of the second encoded channel spectral coefficients, and the minimum of the portion of the first encoded channel spectral coefficients and the portion of the second encoded channel spectral coefficients.

64. The apparatus as claimed in claim 58 wherein the first part is an encoded combined channel time domain audio signal.

65. A method, comprising:

generating an encoded signal comprising at least a first part, a second part and a third part, wherein generating the encoded signal further comprises;

generating the first part of the encoded signal dependent on a received time domain representation of an audio signal comprising at least two channels, and on at least one combination of first and second channels of the at least two channels, wherein each of the at least one combination of the first and second channels comprises an average of at least one time domain sample from the first channel and an associated at least one time domain sample from the second channel;

generating the second part of the encoded signal dependent on at least one difference between the first and second channels of the at least two channels; and

generating the third part of the encoded signal dependent on at least one energy ratio of the first and second channels of the at least two channels.

66. The method as claimed in claim 65, wherein the first part of the encoded signal is a time domain encoded signal.

67. The method as claimed in claim 65, wherein generating the first part comprises applying at least one of:

advanced audio coding (AAC);

MPEG-1 layer 3 (MP3),

ITU-T embedded variable rate (EV-VBR) speech coding base line coding;

adaptive multi rate-wide band (AMR-WB) coding; and

adaptive multi rate wide band plus (AMR-WB+) coding.

68. The method as claimed in claim 65, wherein the first and second channels of the at least two channels are time domain representations, the method further comprising generating a first and second frequency domain representation of the first and second channels, wherein each of the first and second frequency domain representations of the first and second channels comprise at least two spectral coefficient values, and wherein the second part of the encoded signal comprises at least two difference values wherein each difference value is dependent on the difference between a first channel spectral coefficient value and an associated second channel spectral coefficient value.

69. The method as claimed in claim 68, wherein generating the first and second frequency domain representations of the first and second channels comprises transforming the time domain representations of the first and second channels, wherein transforming comprises one of:

a shifted discrete fourier transform;

a modified discrete cosine transform; and

a discrete unitary transform.

70. The method as claimed in claim 68 further comprising grouping the at least two spectral coefficient values from each of the first and second frequency domain representations of the first and second channels into at least two sub-bands, each channel sub-band comprising at least one spectral coefficient value.

71. The method as claimed in claim 70, wherein the third part of the encoded signal comprises at least two energy ratios, wherein each energy ratio is associated with a sub-band, wherein the method comprises generating each energy ratio by determining the ratio, for each associated sub-band, of the maximum of the first and the second channels energies and the minimum of the first and the second channels energies.

72. A method comprising:

dividing the encoded signal received for a first time period into at least a first part, a second part and a third part, wherein the first, second and third parts represent an encoded first and second channels of a multichannel audio signal;

generating a first decoded signal dependent on the first part; and

generating at least one further decoded signal dependent on the first decoded signal, and at least one of the second and third parts of the encoded signal.

73. The method as claimed in claim 72, wherein each of the at least one further decoded signals comprise at least two portions;

the method further comprising;

determining at least one characteristic of the encoded signal associated with at least one portion of the at least one further decoded signal;

selecting one of the second or third parts of the encoded signal dependent on the characteristic associated with the at least one portion of the at least one further decoded signal; and

generating the at least one part of the at least one further decoded signal dependent on the first decoded signal and the selected one of the second or third parts.

74. The method as claimed in claim 73, wherein the characteristic comprises at least one of:

an auditory gain greater than a threshold value;

an auditory scene being wholly located in at least one of the encoded first and second channels; and

the second part not being null.

75. The method as claimed in claim 72, wherein the first decoded signal comprises at least one combined channel frequency domain representation, and wherein each combined channel frequency domain representation comprises at least two combined channel spectral coefficient portions, each combined channel spectral portion comprising at least one spectral coefficient value.

76. The method as claimed in claim 72, wherein the second part of the encoded signal comprises at least one side channel value, and wherein each side channel value is dependent on a difference between a first channel spectral coefficient value and the second encoded channel spectral coefficient value.

77. The method as claimed in claim 72, wherein the third part of the encoded signal comprises at least one intensity side channel encoded value, and wherein each intensity side channel encoded value comprises an encoded energy ratio between the maximum of a portion of the first encoded channel spectral coefficients and a portion of the second encoded channel spectral coefficients, and the minimum of the portion of the first encoded channel spectral coefficients and the portion of the second encoded channel spectral coefficients.

78. The method as claimed in claim 72, wherein the first part is an encoded combined channel time domain audio signal.