Methods, devices and computer program products for compressing an audio signal

• US 6,741,966 B2
• Filed: 01/22/2001
• Issued: 05/25/2004
• Est. Priority Date: 01/22/2001
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Romesburg, Eric Douglas
• Primary Examiner(s): MCFADDEN, SUSAN IRIS
• Application Number:
  US09/766,783
• Publication Number:
  US 20020133356A1
• Time in Patent Office: 1,219 Days
• Field of Search: 704/500, 704/501, 704/502, 704/503, 704/504
• US Class Current: 704/500
• CPC Class Codes: H03G 7/007 of digital or coded signals

Abstract

A method of compressing an audio signal can include accepting input samples of the audio signal wherein the input samples include non-zero input samples. A logarithm of each of the non-zero input samples of the audio signal can be calculated. Compressed output samples for each non-zero input sample can then be determined based on the logarithm of each respective non-zero input sample. Preferably, a linear relationship may exist between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples. A logarithm of each compressed output sample, corresponding to a non-zero input sample, may be based on a product of a logarithm of each corresponding non-zero input sample and a compression factor. Related devices and computer program products are also discussed.

Claims

1. A method of compressing an audio signal, the method comprising:

accepting input samples of the audio signal wherein the input samples include non-zero input samples and wherein the input samples including the non-zero input samples are included in one radiotelephone communications frame of a plurality of radiotelephone communications frames;

calculating a logarithm of each of the non-zero input samples of the radiotelephone communications frame of the audio signal; and

determining a compressed output sample for each non-zero input sample of the radiotelephone communications frame based on the logarithm of each respective non-zero input sample of the radiotelephone communications frame.

2. A method according to claim 1 wherein determining a compressed output sample for each non-zero input sample comprises applying compression on a frame by frame basis.

3. A method according to claim 1, wherein a linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

4. A method according to claim 3, wherein the logarithm of each compressed output sample corresponding to a non-zero input sample is further based on the product of the logarithm of each corresponding non-zero input sample and the compression factor plus a logarithm of a system gain.

5. A method according to claim 1, wherein a logarithm of each compressed output sample, corresponding to a non-zero input sample, is based on a product of a logarithm of each corresponding non-zero input sample and a compression factor.

6. A method according to claim 5, wherein the compression factor is based on at least one of the logarithm of a clipping level, a logarithm of a system gain, and a logarithm of an absolute value of a peak input sample.

7. A method according to claim 6, wherein the compression factor is based on a difference between the logarithm of the clipping level and the logarithm of the system gain.

8. A method according to claim 7, wherein the compression factor is based on a difference between the logarithm of a clipping level and the logarithm of the system gain, wherein the difference is divided by the logarithm of the absolute value of the peak input sample.

9. A method according to claim 6, wherein the peak input sample is one of the plurality of input samples for which a compressed output sample is calculated.

10. A method according to claim 6, wherein the peak input sample is a peak input sample prior to the input samples for which compressed output samples are determined.

11. A method according to claim 3, wherein the system gain is variable for each of the non-zero input samples.

12. A method according to claim 1, further comprising:

providing a measurement for each of the non-zero samples, wherein determining the compression for each of the non-zero input samples is further based on the measurement for one of the samples.

13. A method according to claim 12, wherein providing a measurement for each of the non-zero input samples further comprises determining one of the non-zero input samples having a peak absolute value, wherein determining the compression for each of the non-zero samples is further based on the peak absolute value.

14. A method of compressing an audio signal, the method comprising:

accepting a radiotelephone communications frame including input samples of the audio signal wherein the radiotelephone communications frame of input samples includes non-zero input samples and wherein the frame is one of a plurality of radiotelephone communications frames of the audio signal;

providing a measurement of one of the non-zero input samples of the radiotelephone communications frame; and

determining compressed output samples for each non-zero input sample of the radiotelephone communications frame based on the measurement of one of the non-zero input samples of the radiotelephone communications frame.

15. A method according to claim 14, wherein the step of providing a measurement of one of the non-zero input samples of the frame, further comprises determining an absolute value of a peak non-zero input sample of the frame, wherein determining compressed output samples for each non-zero input sample of the frame is based on the absolute value of the peak non-zero input sample of the frame.

16. A method according to claim 15, further comprising:

calculating a logarithm of the absolute value of the peak non-zero input sample of the frame.

17. A method according to claim 16, wherein the step of determining compressed output samples for each non-zero input sample of the frame comprises determining compressed output samples for each non-zero input sample of the frame based on the logarithm of the absolute value of the peak non-zero input sample of the frame.

18. A method according to claim 14, wherein a linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

19. A method according to claim 14, wherein a logarithm of each compressed output sample corresponding to a non-zero input sample is based on a product of a logarithm of each corresponding non-zero input sample and a compression factor plus a logarithm of a system gain.

20. A method according to claim 19, wherein the compression factor is equal to the logarithm of the peak absolute value of the non-zero input sample of the frame.

21. A method according to claim 19, wherein the system gain is variable for each non-zero input sample.

22. A method according to claim 21, wherein providing a measurement of one of the non-zero input samples of the frame comprises determining an absolute value of a peak product of each non-zero input sample of the frame and a corresponding variable system gain.

23. A method according to claim 14 wherein determining compressed output samples for each non-zero input sample comprises applying compression on a frame by frame basis.

24. A method of compressing an audio signal, the method comprising:

accepting input samples of the audio signal wherein the input samples include non-zero input samples and wherein the input samples are included in one radiotelephone communications frame of a plurality of radiotelephone communications frames;

providing an absolute value of a peak non-zero input sample of the radiotelephone communications frame; and

determining compressed output samples for at least a plurality of the non-zero input samples of the radiotelephone communications frame based on the absolute value of the peak non-zero input sample of the radiotelephone communications frame.

25. A method according to claim 24, further comprising:

calculating a logarithm of the absolute value of the peak non-zero input sample.

26. A method according to claim 24, wherein a common linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

27. A method according to claim 26, wherein a logarithm of each compressed output sample is based on a product of a logarithm of a corresponding non-zero input sample and a compression factor.

28. A method according to claim 26, wherein a logarithm of each compressed output sample is based on a product of a logarithm of a corresponding non-zero input sample and a compression factor plus a logarithm of a system gain.

29. A method according to claim 28, wherein the system gain is variable for each non-zero input sample.

30. A method according to claim 24, wherein the input samples comprise at least two frames of input samples and wherein the peak non-zero input sample is from a first frame and wherein the compressed output samples correspond to non-zero input samples of a second frame.

31. A method according to claim 24 wherein determining compressed output samples comprises applying compression on a frame by frame basis.

32. A computer program product for compressing an audio signal, the computer program product comprising a computer-readable storage medium having computer-readable program code embodied therein, the computer-readable program code comprising:

computer-readable program code that accepts input samples of the audio signal wherein the input samples include non-zero input samples and wherein the input samples including the non-zero input samples are included in one radiotelephone communications frame of a plurality of radiotelephone communications frames;

computer-readable program code that calculates a logarithm of each of the non-zero input samples of the radiotelephone communications frame of the audio signal; and

computer-readable program code that determines a compressed output sample for each non-zero input sample of the radiotelephone communications frame based on the logarithm of each respective non-zero input sample of the radiotelephone communications frame.

33. A computer program product according to claim 32, wherein a linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

34. A computer program product according to claim 33, wherein the system gain is variable for each of the non-zero input samples.

35. A computer program product according to claim 32, wherein a logarithm of each compressed output sample, corresponding to a non-zero input sample is based on a product of a logarithm of each corresponding non-zero input sample and a compression factor.

36. A computer program product according to claim 33, wherein the logarithm of each compressed output sample corresponding to a non-zero input sample is further based on the product of the logarithm of each corresponding non-zero input sample and the compression factor plus a logarithm of a system gain.

37. A computer program product according to claim 35, wherein the compression factor is based on at least one of the logarithm of a clipping level, a logarithm of a system gain, and a logarithm of an absolute value of a peak input sample.

38. A computer program product according to claim 37, wherein the compression factor is based on a difference between the logarithm of the clipping level and the logarithm of the system gain.

39. A computer program product according to claim 38, wherein the compression factor is based on a difference between the logarithm of a clipping level and the logarithm of the system gain, wherein the difference is divided by the logarithm of the absolute value of the peak input sample.

40. A computer program product according to claim 37, wherein the peak input sample is one of the plurality of input samples for which a compressed output sample is calculated.

41. A computer program product according to claim 37, wherein the peak input sample is a peak input sample prior to the input samples for which compressed output samples are determined.

42. A computer program product according to claim 32, further comprising:

computer-readable program code that provides a measurement for each of the non-zero samples, wherein the determining the compression for each of the non-zero input samples is further based on the measurement for one of the samples.

43. A computer program product according to claim 42, wherein providing a measurement for each of the non-zero input samples further comprises determining one of the non-zero input samples having a peak absolute value, wherein determining the compression for each of the non-zero samples is further based on the peak absolute value.

44. A computer program product according to claim 32 wherein the computer-readable program code that determined a compressed output sample for each non-zero input sample applies compression on a frame by frame basis.

45. A computer program product for compressing an audio signal, the computer program product comprising a computer-readable storage medium having computer-readable program code embodied in the medium, the computer-readable program code comprising:

computer-readable program code that accepts a radiotelephone communications frame of input samples of the audio signal wherein the radiotelephone communications frame of input samples includes non-zero input samples and wherein the frame is one of a plurality of radiotelephone communications frames of the audio signal;

computer-readable program code that provides a measurement of one of the non-zero input samples of the radiotelephone communications frame; and

computer-readable program code that determines compressed output samples for each non-zero input sample of the radiotelephone communications frame based on the measurement of one of the non-zero input samples of the radiotelephone communications frame.

46. A computer program product according to claim 45, wherein providing a measurement of one of the non-zero input samples of the frame further comprises determining an absolute value of a peak non-zero input sample of the frame, wherein determining compressed output samples for each non-zero input sample of the frame is based on the absolute value of the peak non-zero input sample of the frame.

47. A computer program product according to claim 46, further comprising:

computer-readable program code that calculates a logarithm of the absolute value of the peak non-zero input sample of the frame.

48. A computer program product according to claim 47, wherein determining compressed output samples for each non-zero input sample of the frame comprises determining compressed output samples for each non-zero input sample of the frame based on the logarithm of the absolute value of the peak non-zero input sample of the frame.

49. A computer program product according to claim 45, wherein a linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

50. A computer program product according to claim 45, wherein a logarithm of each compressed output sample corresponding to a non-zero input sample is based on a product of a logarithm of each corresponding non-zero input sample and a compression factor plus a logarithm of a system gain.

51. A computer program product according to claim 50, wherein the compression factor is equal to the logarithm of the peak absolute value of the non-zero input sample of the frame.

52. A computer program product according to claim 50, wherein the system gain is variable for each non-zero input sample.

53. A computer program product according to claim 52, wherein providing a measurement of one of the non-zero input samples of the frame comprises determining an absolute value of a peak product of each non-zero input sample of the frame and a corresponding variable system gain.

54. A computer program product according to claim 45 wherein the computer-readable program code that determines compressed output samples for each non-zero input sample applies compression on a frame by frame basis.

55. A computer program product for compressing an audio signal, the computer program product comprising a computer-readable storage medium having computer-readable program code embodied in the medium, the computer-readable program code comprising:

computer-readable program code that accepts input samples of the audio signal wherein the input samples include non-zero input samples and wherein the input samples are included in one radiotelephone communications frame of a plurality of radiotelephone communications frames;

computer-readable program code that provides an absolute value of a peak non-zero input sample of the radiotelephone communications frame; and

computer-readable program code that determines compressed output samples for at least a plurality of the non-zero input samples of the radiotelephone communications frame based on the absolute value of the peak non-zero input sample of the radiotelephone communications frame.

56. A computer program product according to claim 55, wherein a common linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

57. A computer program product according to claim 56, wherein a logarithm of each compressed output sample is based on a product of a logarithm of a corresponding non-zero input sample and a compression factor.

58. A computer program product according to claim 56, wherein a logarithm of each compressed output sample is based on a product of a logarithm of a corresponding non-zero input sample and a compression factor plus a logarithm of a system gain.

59. A computer program product according to claim 58, wherein the system gain is variable for each non-zero input sample.

60. A computer program product according to claim 55, wherein the input samples comprise at least two frames of input samples and wherein the peak non-zero input sample is from a first frame and wherein the compressed output samples correspond to non-zero input samples of a second frame.

61. A computer program product according to claim 55, further comprising:

computer-readable program code that calculates a logarithm of the absolute value of the peak non-zero input sample.

62. A computer program product according to claim 55 wherein the computer-readable program code that determines compressed output samples applies compression on a frame by frame basis.

63. A communications device comprising:

an audio processing unit that provides input samples of the audio signal wherein the input samples include non-zero input samples and wherein the input samples including the non-zero input samples are included in one radiotelephone communications frame of a plurality of radiotelephone communications frames; and

a compressor that calculates a logarithm of each of the non-zero input samples of the radiotelephone communications frame of the audio signal, and that determines a compressed output sample for each non-zero input sample of the radiotelephone communications frame based on the logarithm of each respective non-zero input sample of the radiotelephone communications frame.

64. A communications device according to claim 63, wherein a linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

65. A communications device according to claim 64, wherein the logarithm of each compressed output sample corresponding to a non-zero input sample is further based on the product of the logarithm of each corresponding non-zero input sample and the compression factor plus a logarithm of a system gain.

66. A communications device according to claim 64, wherein the system gain is variable for each of the non-zero input samples.

67. A communications device according to claim 63, wherein a logarithm of each compressed output sample, corresponding to a non-zero input sample, is based on a product of a logarithm of each corresponding non-zero input sample and a compression factor.

68. A communications device according to claim 67, wherein the compression factor is based on at least one of the logarithm of a clipping level, a logarithm of a system gain, and a logarithm of an absolute value of a peak input sample.

69. A communications device according to claim 68, wherein the peak input sample is one of the plurality of input samples for which a compressed output sample is calculated.

70. A communications device according to claim 68, wherein the peak input sample is a peak input sample prior to the input samples for which compressed output samples are determined.

71. A communications device according to claim 68, wherein the compression factor is based on a difference between the logarithm of the clipping level and the logarithm of the system gain.

72. A communications device according to claim 71, wherein the compression factor is based on a difference between the logarithm of a clipping level and the logarithm of the system gain, wherein the difference is divided by the logarithm of the absolute value of the peak input sample.

73. A communications device according to claim 63, wherein the compressor provides a measurement for each of the non-zero samples, and wherein determining the compression for each of the non-zero input samples is further based on the measurement for one of the samples.

74. A communications device according to claim 73, wherein providing a measurement for each of the non-zero input samples further comprises determining one of the non-zero input samples having a peak absolute value, wherein determining the compression for each of the non-zero samples is further based on the peak absolute value.

75. A communications device according to claim 63, wherein the compressor applies compression on a frame by frame basis.

76. A communications device comprising:

an audio processing unit that provides a radiotelephone communications frame of input samples of the audio signal wherein the radiotelephone communications frame of input samples includes non-zero input samples and wherein the frame is one of a plurality of radiotelephone communications frames of the audio signal;

a compressor that provides a measurement of one of the non-zero input samples of the radiotelephone communications frame, and that determines compressed output samples for each non-zero input sample of the radiotelephone communications frame based on the measurement of one of the non-zero input samples of the radiotelephone communications frame.

77. A communications device according to claim 76, wherein providing a measurement of one of the non-zero input samples of the frame further comprises determining an absolute value of a peak non-zero input sample of the frame, wherein determining compressed output samples for each non-zero input sample of the frame is based on the absolute value of the peak non-zero input sample of the frame.

78. A communications device according to claim 77, wherein the compressor calculates a logarithm of the absolute value of the peak non-zero input sample of the frame.

79. A communications device according to claim 78, wherein determining compressed output samples for each non-zero input sample of the frame comprises determining compressed output samples for each non-zero input sample of the frame based on the logarithm of the absolute value of the peak non-zero input sample of the frame.

80. A communications device according to claim 76, wherein a linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

81. A communications device according to claim 76, wherein a logarithm of each compressed output sample corresponding to a non-zero input sample is based on a product of a logarithm of each corresponding non-zero input sample and a compression factor plus a logarithm of a system gain.

82. A communications device according to claim 81, wherein the compression factor is equal to the logarithm of the peak absolute value of the non-zero input sample of the frame.

83. A communications device according to claim 81, wherein the system gain is variable for each non-zero input sample.

84. A communications device according to claim 83, wherein providing a measurement of one of the non-zero input samples of the frame comprises determining an absolute value of a peak product of each non-zero input sample of the frame and a corresponding variable system gain.

85. A communications device according to claim 76 wherein the compressor applies compression on a frame by frame basis.

86. A communications device comprising:

an audio processing unit that provides input samples of the audio signal wherein the input samples include non-zero input samples and wherein the input samples are included in one radiotelephone communications frame of a plurality of radiotelephone communications frames; and

a compressor that provides an absolute value of a peak non-zero input sample of the radiotelephone communications frame, and that determines compressed output samples for at least a plurality of the non-zero input samples of the radiotelephone communications frame based on the absolute value of the peak non-zero input sample of the radiotelephone communications frame.

87. A communications device according to claim 86, wherein the compressor calculates a logarithm of the absolute value of the peak non-zero input sample.

88. A communications device according to claim 86, wherein a common linear relationship exists between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples.

89. A communications device according to claim 88, wherein a logarithm of each compressed output sample is based on a product of a logarithm of a corresponding non-zero input sample and a compression factor.

90. A communications device according to claim 88, wherein a logarithm of each compressed output sample is based on a product of a logarithm of a corresponding non-zero input sample and a compression factor plus a logarithm of a system gain.

91. A communications device according to claim 90, wherein the system gain is variable for each non-zero input sample.

92. A communications device according to claim 86, wherein the input samples comprise at least two frames of input samples and wherein the peak non-zero input sample is from a first frame and wherein the compresses output samples correspond to non-zero input samples of a second frame.

93. A communications device according to claim 86 wherein the compressor applies compression on a frame by frame basis.