Digital audio data transmission system based on the information content of an audio signal

• US 5,809,472 A
• Filed: 04/03/1996
• Issued: 09/15/1998
• Est. Priority Date: 04/03/1996
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Original Assignee: Command Audio Corporation
• Inventors: Morrison, Eric Fraser
• Primary Examiner(s): Hudspeth, David R.
• Assistant Examiner(s): Storm, Donald L.
• Application Number:
  US08/627,947
• Time in Patent Office: 895 Days
• Field of Search: 395/2.91, 395/2.1, 395/2.92, 395/2.15, 395/2.75, 395/2.94, 370/435, 370/521, 370/341, 380/9, 704/229, 704/230, 704/222, 704/233, 704/200
• US Class Current: 704/500
• CPC Class Codes: H04H 20/88 Stereophonic broadcast systems multiplex system in general H04J

Abstract

The data rate of speech and non-speech audio is selectively reduced by respective compression techniques based upon the information content of the type of signal. A composite audio information signal formed of speech and non-speech audio is applied to both a voice encoder and a wide-band audio compression encoder. An audio-type detection circuit examines the speech spectrum as well as the entire frequency spectrum and dynamic range of the audio information and generates a selection signal indicating whether the signal is speech or non-speech audio. A composite encoded audio signal is produced by intermingling the outputs of the encoders in response to the selection signal. The composite encoded audio signal and an identification signal indicative of the audio signal type are transmitted to respective receivers at the reduced data rates for storage, and subsequent decoding and retrieval by a listener as an audible signal in response to the transmitted identification signal.

Claims

1. Apparatus for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising:

means for generating a selection signal indicative of the speech signal and the non-speech signal;

means for separately encoding the speech and non-speech signals present in the audio information with optimum compression based on the energy contents of the signals;

means responsive to the selection signal for providing an identification signal indicative of the audio signals for inclusion with selected audio signals; and

means for intermingling the encoded speech signal, and the encoded non-speech signal and the identification signal in response to the selection signal.

2. The apparatus of claim 1 wherein the generating means includes:

means for detecting whether the information is a speech signal or a non-speech signal; and

the generating means being responsive to the detecting means.

3. The apparatus of claim 2 wherein the detecting means includes:

first means for generating a first signal indicative of a speech signal;

second means for generating a second signal indicative of a non-speech signal; and

logic for generating the selection signal in response to the first and second signals.

4. The apparatus of claim 3 wherein the first signal is representative of a preselected ratio of pauses in the audio information to indicate the speech signal.

5. The apparatus of claim 3 wherein the first means includes:

a filter for passing a passband signal in a frequency range which contains maximum speech energy; and

a pause detector responsive to the filter for generating the first signal indicative of an occurrence of successive pauses in the audio information.

6. Apparatus for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising:

means responsive to a selection signal for providing an identification signal indicative of the audio signals for inclusion with selected audio signals;

means for intermingling the speech signal, the non-speech signal, and the identification signal in response to the selection signal;

first means for generating a first signal indicative of a speech signal;

logic for generating the selection signal in response to the first signal and a second signal;

a filter for passing a passband signal in a frequency range which contains maximum speech energy;

means responsive to the passband signal and the audio information for providing a third signal representing a level of frequency components outside a range of the speech signal; and

means responsive to the third signal and to a predetermined threshold level for producing the second signal indicative of a level of energy in the third signal.

7. The apparatus of claim 6 wherein the producing means includes an audio level threshold circuit for comparing the third signal with the predetermined threshold level.

8. The apparatus of claim 6 wherein the logic includes AND logic responsive to logic states of the first signal and the second signal, for generating said selection signal.

9. The apparatus of claim 6 further including a voice encoder for encoding the speech signal:

wherein the voice encoder is selected by the means for intermingling when the selection signal indicates speech.

10. The apparatus of claim 6 further including a wide-band audio compression encoder for encoding the non-speech signal:

wherein the wide-band encoder is selected by the means for intermingling when the selection signal indicates non-speech.

11. Apparatus for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising:

means for generating a selection signal indicative of the speech signal and the non-speech signal;

means responsive to the selection signal for providing an identification signal indicative of the audio signals for inclusion with selected audio signals;

means for intermingling encoded speech signal, the encoded non-speech signal, and the identification signal in response to the selection signal;

a voice encoder for encoding the speech signal; and

a wide-band audio compression encoder for encoding the non-speech signal.

12. Apparatus for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising:

means for generating a selection signal indicative of the speech signal and the non-speech signal;

means responsive to the selection signal for providing an identification signal indicative of the audio signals for inclusion with selected audio signals;

means for intermingling the speech signal, the non-speech signal, and the identification signal in response to the selection signal;

a timing generator means responsive to the selection signal for synchronizing the identification signal with the occurrence of the audio signals; and

a latch responsive to the timing generator means for providing the identification signal.

13. The apparatus of claim 12, wherein the audio signals include an ASCII text signal, and further including:

a buffer for selectively supplying the ASCII text signal; and

the timing generator means being responsive to the buffer for storing the speech and non-speech signals in response to the buffer supplying the ASCII text signal.

14. Apparatus for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising:

means responsive to a selection signal for providing an identification signal indicative of the audio signals for inclusion with selected audio signals; and

means for intermingling the speech signal, the non-speech signal, and the identification signal in response to the selection signal;

a voice encoder for receiving and compressing the audio signals;

means for generating reconstructed voice coded signals from the compressed audio signals;

means for comparing the accuracy of the reconstructed voice coded signals with the audio signals; and

means for generating the selection signal indicative of a speech signal in response to an accurate comparison between the reconstructed audio signals and the audio signals and for generating a selection signal indicative of a non-speech signal in response to a significant inaccuracy in the comparison.

15. The apparatus of claim 14 wherein the means for comparing further includes a threshold circuit.

16. Apparatus for reducing the transmission data rate of digital audio information formed of speech signals and non-speech signals, comprising:

means for detecting whether the information is a speech or a non-speech signal and for generating a selection signal indicative thereof;

means for separately encoding the speech and non-speech signals with respective optimum compression based on the information energy content of the signals;

means responsive to the detecting and generating means for producing a signal identifying the speech signal and the non-speech signal; and

means for intermingling the encoded speech signal and the encoded non-speech signal in response to the selection signal, for transmission at said reduced data rate.

17. The apparatus of claim 16 wherein the detecting means includes:

means for generating a first signal indicative of the occurrence of a large number of pauses in a unit of time in a selected frequency range of the audio information corresponding to a speech signal; and

means for generating a second signal indicative of audio frequency components outside the selected frequency range corresponding to a non-speech signal.

18. The apparatus of claim 17 wherein the means for generating a selection signal includes:

logic for producing in response to the first and second signals a logic state identifying the presence of a speech signal or a non-speech signal.

19. The apparatus of claim 17 wherein the first signal generating means includes:

a filter for providing a passband signal of said selected frequency range; and

a pause detector responsive to the passband signal for generating a logic state corresponding to said first signal.

20. The apparatus of claim 19 wherein:

the filter provides a passband in a frequency range of maximum speech energy; and

the logic is an AND gate.

21. The apparatus of claim 17 wherein the second signal generating means includes:

means responsive to a passband signal of said selected frequency range and the audio information for providing a third signal representing a level of audio frequency components outside the selected frequency range; and

means responsive to the third signal for providing a logic state corresponding to said second signal.

22. The apparatus of claim 21 wherein:

the means for providing a third signal is a subtractor for subtracting the passband signal from the audio information; and

the means for providing a logic state includes a threshold input of a selected audio level for comparison to the third signal.

23. The apparatus of claim 16 wherein:

the encoding means includes a voice coder for encoding the speech signal and a wide-band audio compression encoder for encoding the non-speech signal; and

the intermingling means includes a selector/multiplexer circuit for selecting the encoded speech signal, the encoded non-speech signal or the identifying signal in response to the selection signal.

24. The apparatus of claim 16 including:

means for transmitting the intermingled encoded speech and non-speech signals selected by the means for intermingling along with the identifying signal; and

a receiver receiving the transmitted encoded speech and non-speech signals for selectively decoding in response to the identifying signal the transmitted encoded speech and non-speech signals into a reassembled audio signal corresponding to the digital audio information, for audible presentation.

25. The apparatus of claim 24 wherein the receiver includes:

a memory for storing the transmitted signals;

means coupled to the memory for separating the identifying signal from the encoded speech and non-speech signals;

a decoder for separately decoding each of the encoded speech and non-speech signals; and

a switch for selecting the decoded speech or non-speech signal in response to the separated identifying signal to form the reassembled audio signal for audible presentation.

26. Apparatus for decoding digital audio information formed of signals such as speech signals and non-speech signals, the audio information including a signal identifying the speech and non-speech signals, comprising:

means for receiving combined speech, non-speech and identifying signals;

means for separating the identifying signal from the speech and non-speech signals; and

a decoder for separately decoding the speech and non-speech signals into a reassembled audio signal in response to the identifying signal, for audible presentation of the reassembled audio.

27. The apparatus of claim 26 wherein the means for separating includes:

a decoder circuit for detecting the identifying signal and extracting it from the combined signals.

28. The apparatus of claim 26 wherein the means for receiving includes:

means for storing the combined speech, non-speech and identifying signals; and

means for retrieving the stored signals.

29. Apparatus for encoding digital audio information formed of audio signals such as speech signals and non-speech signals, comprising:

a generator which provides a selection signal indicative of the speech signal and the non-speech signal;

an encoder that separately encodes the speech and non-speech signals present in the audio information with optimum compression based on the information energy content of the signals;

a circuit responsive to the selection signal that provides an identification signal indicative of the audio signals for inclusion with selected audio signals; and

a multiplexer coupled to receive the encoded speech signal, the encoded non-speech signal, and the identification signal that intermingles the encoded speech signal, the encoded non-speech signal and the identification signal in response to the selection signal.

30. The apparatus of claim 29 wherein the generator includes:

a detector that detects whether the information is a speech signal or a non-speech signal; and

the generator being responsive to the detector.

31. The apparatus of claim 30 wherein the detector includes:

a first circuit that generates a first signal indicative of a speech signal;

a second circuit that generates a second signal indicative of a non-speech signal; and

a logic coupled to receive the first and second signals that generates the selection signal in response to the first and second signals.

32. The apparatus of claim 31 wherein the first signal is representative of a preselected ratio of pauses in the audio information to indicate the speech signal.

33. The apparatus of claim 31 where the first circuit includes:

a filter that passes a passband signal in a frequency range which contains the maximum speech energy; and

a pause detector responsive to the filter that generates the first signal indicative of an occurrence of successive pauses in the audio information.

34. Apparatus for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising:

a generator coupled to receive first and second signals that generates a selection signal indicative of speech and non-speech signals;

a circuit responsive to the selection signal that provides an identification signal indicative of the audio signals for inclusion with selected audio signals;

a multiplexer coupled to receive the speech signal, the non-speech signal, and the identification signal that intermingles the speech signal, the non-speech signal, and the identification signal in response to the selection signal;

a first circuit that generates the first signal indicative of a speech signal;

a filter that passes a passband signal in a frequency range which contains maximum speech energy;

a third circuit responsive to the passband signal and the audio information that provides a third signal representing a level of frequency components outside the range of the speech signal; and

a logic responsive to the third signal and to a predetermined threshold level for producing the second signal indicative of the level of energy in the third signal.

35. The apparatus of claim 34 wherein the logic further includes an audio level threshold circuit that compares the third signal with the predetermined threshold level.

36. The apparatus of claim 34 wherein the generator further includes AND logic responsive to logic states of the first signal and the second signal for generating the selection signal.

37. The apparatus of claim 34 further including a voice encoder that encodes the speech signal;

wherein the voice encoder is selected by the multiplexer where the selection signal indicates a speech signal.

38. The apparatus of claim 34 further including a wide-band audio compression encoder that encodes the non-speech signal;

wherein the wide-band encoder is selected by the multiplexer where the selection signal indicates a non-speech signal.

39. Apparatus for encoding digital audio information formed of audio signals such as speech signals and non-speech signals, comprising:

a generator which provides a selection signal indicative of the speech signal and the non-speech signal;

a circuit responsive to the selection signal that provides an identification signal indicative of the audio signals for inclusion with selected audio signals;

a multiplexer coupled to receive an encoded speech signal, an encoded non-speech signal, and the identification signal that intermingles the encoded speech signal, the encoded non-speech signal, and the identification signal in response to the selection signal;

a voice encoder that encodes the speech signal;

a wide-band audio compression encoder that encodes the non-speech signal.

40. Apparatus for encoding digital audio information formed of audio signals such as speech signals and non-speech signals, comprising:

a generator which provides a selection signal indicative of the speech signal and the non-speech signal;

a circuit responsive to the selection signal that provides an identification signal indicative of the audio signals for inclusion with selected audio signals;

a multiplexer coupled to receive the speech signal, the non-speech signal, and the identification signal that intermingles the speech signal, the non-speech signal, and the identification signal in response to the selection signal;

a timing generator that synchronizes the identification signal with the occurrence of the speech and non-speech signals; and

a latch responsive to the timing generator that provides the identification signal.

41. The apparatus of claim 40 wherein the audio signals include an ASCII text signal, including:

a buffer that selectively supplies the ASCII text signal to the multiplexer; and

the timing generator is responsive to a buffer for storing the speech and non-speech signals in response to the buffer supplying the ASCII text signal.

42. Apparatus for encoding digital audio information formed of audio signals such as speech signals and non-speech signals, comprising:

a circuit responsive to a selection signal that provides an identification signal indicative of the audio signals for inclusion with selected audio signals;

a multiplexer coupled to receive the speech signal, the non-speech signal, and the identification signal that intermingles the speech signal, the non-speech signal, and the identification signal in response to a selection signal;

a voice encoder that receives and compresses the audio signals;

a comparator that compares the accuracy of reconstructed voice coded signals generated from the compressed audio signals with the audio signals; and

a generator that generates the selection signal indicative of a speech signal in response to an accurate comparison between the reconstructed audio signals and the audio signals and that generates the selection signal indicative of a non-speech signal in response to a significant inaccuracy in the comparison.

43. The apparatus of claim 42 wherein the comparator includes a threshold circuit.

44. Method for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising the steps:

generating a selection signal indicative of the speech signal and the non-speech signal;

separately encoding the speech and non-speech signals present in the audio information with optimum compression based on the energy contents of the signals;

providing an identification signal indicative of the audio signals for inclusion with selected audio signals in response to the selection signal; and

intermingling the encoded speech signal, the encoded non-speech signal, and the identification signal in response to the selection signal.

45. The method of claim 44 wherein the generating step further includes the step of:

detecting whether the information is a speech signal or a non-speech signal.

46. The method of claim 45 wherein the generating step further includes the steps of:

generating a first signal indicative of the speech signal;

generating a second signal indicative of the non-speech signal; and

generating the selection signal in response to the first and second signals.

47. The method of claim 46 wherein the step of generating the first signal further includes the steps of:

filtering out signals except a passband signal in a frequency range which contains maximum speech energy;

detecting pauses in the passband signal; and

generating the first signal indicative of speech where there is an occurrence of successive pauses in the audio information.

48. Method for encoding digital audio information formed of audio signals including speech signals and non-speech signals, comprising the steps of:

generating a first signal indicative of the speech signal;

filtering out signals except a passband signal in a frequency range which contains maximum speech energy;

providing a third signal responsive to the passband signal and the audio information representing a level of frequency components outside the range of the speech signal;

generating a second signal responsive to the third signal indicative of the non-speech signal;

generating a selection signal indicative of the speech signal and the non-speech signal in response to the first and second signals;

separately encoding the speech and non-speech signals present in the audio information with optimum compression based on the energy contents of the signals;

providing an identification signal indicative of the audio signals for inclusion with selected audio signals in response to the selection signal; and

intermingling the encoded speech signal, the encoded non-speech signal, and the identification signal in response to the selection signal.

49. The method of claim 48 wherein the step of generating a second signal further includes the steps of:

comparing the third signal with a predetermined threshold level; and

generating the second signal as indicating non-speech where the third signal exceeds the predetermined threshold level.

50. The method of claim 48 wherein the step of generating a selection signal further includes the steps of:

generating a selection signal indicative of non-speech where the second signal indicates non-speech;

or

generating a selection signal indicative of speech where the first signal indicates speech and the second signal does not indicate non-speech.

51. The method of claim 48 wherein the step of separately encoding further includes the steps of:

voice encoding the speech signal; and

wide-band compression encoding the non-speech signal.

52. The method of claim 51 wherein the step of intermingling further includes:

selecting the voice encoded signal when the selection signal indicates the speech signal;

or

selecting the wide-band compression encoded signal when the selection signal indicates the non-speech signal.

53. Method for encoding digital audio information formed of audio signals including speech signals and non-speech signals, the steps comprising:

generating a selection signal indicative of the speech signal and the non-speech signal;

voice encoding the speech signal;

wide-band compression encoding the non-speech signal;

providing an identification signal indicative of the audio signals for inclusion with selected audio signals in response to the selection signal; and

intermingling the encoded speech signal, the encoded non-speech signal, and the identification signal in response to the selection signal.

54. Method for encoding digital audio information formed of audio signals including speech signals and non-speech signals, the steps comprising:

generating a selection signal indicative of the speech signal and the non-speech signal;

providing an identification signal indicative of the audio signals for inclusion with selected audio signals in response to the selection signal;

generating a timing signal responsive to the selection signal for synchronizing the identification signal with the speech and non-speech signals;

synchronizing the identification signal with the speech and non-speech signals by use of a latch responsive to the timing signal; and

intermingling the speech signal, the non-speech signal, and the identification signal in response to the selection signal.

55. The method of claim 54, wherein the speech and non-speech signals include an ASCII text signal, and further including the steps:

storing the ASCII text signal in a buffer;

storing the speech and non-speech signals when the ASCII text is supplied for use in the intermingling step; and

supplying the speech and non-speech signals for use in the intermingling step after the ASCII text has been supplied.

56. Method for encoding digital audio information formed of audio signals including speech signals and non-speech signals, the steps comprising:

voice encoding the audio signals;

reconstructing audio signals from the voice encoded audio signals;

comparing the accuracy of the reconstructed audio signals with the audio signals;

generating a selection signal indicative of a speech signal in response to an accurate reproduction of the audio signals;

or

generating a selection signal indicative of a non-speech signal in response to an inaccurate reproduction of the audio signals;

providing an identification signal indicative of the audio signals for inclusion with selected audio signals in response to the selection signal; and

intermingling the speech signal, the non-speech signal, and the identification signal in response to the selection signal.

57. The method of claim 56 wherein the step of comparing further includes the step of comparing the difference between the reconstructed audio signal and the audio signal with a selected threshold level.

58. Apparatus for reducing the transmission data rate of digital audio information formed of speech signals and non-speech signals, comprising:

a detector coupled to receive the audio information that detects whether the information is a speech or a non-speech signal and generates a selection signal indicative thereof;

an encoder coupled to receive the speech and non-speech signals that separately encodes the speech and non-speech signals with respective optimum compression based on the information energy content of the signals;

an identifier which is responsive to the selection signal that produces a signal identifying the presence of the speech signal and the non-speech signal in the audio information; and

a multiplexer coupled to receive the encoded speech and non-speech signals that intermingles the encoded speech signal and the encoded non-speech signal in response to the selection signal, for transmission at said reduced data rate.

59. The apparatus of claim 58 wherein the detector includes:

a first signal generator that generates a first signal indicative of a large number of pauses in a unit of time in a selected frequency range of the audio information corresponding to the speech signal; and

a second signal generator that generates a second signal indicative of audio frequency components present outside the selected frequency range corresponding to the non-speech signal.

60. The apparatus of claim 59 wherein the detector includes:

a logic coupled to receive the first and second signals that produces a logic state identifying the speech signal or non-speech signal.

61. The apparatus of claim 59 wherein the first signal generator includes:

a filter that provides a passband signal of said selected frequency range; and

a pause detector coupled to receive the passband signal that generates the first signal indicative of the presence of speech where there is an occurrence of successive pauses in the audio information.

62. The apparatus of claim 61 wherein:

the filter provides a passband in a frequency range of maximum speech energy.

63. The apparatus of claim 59 wherein the second signal generator includes:

a third signal generator coupled to receive a passband signal of said selected frequency range and the audio information that provides a third signal representing the level of audio frequency components outside the selected frequency range; and

a threshold circuit coupled to receive the third signal that provides a logic state corresponding to said second signal.

64. The apparatus of claim 63 wherein:

the third signal generator is a subtractor that subtracts the passband signal from the audio information; and

the threshold circuit includes an input of a selected audio level for comparison to the third signal.

65. The apparatus of claim 58 wherein:

the encoder includes a voice coder that encodes the speech signal and a wide-band audio compression encoder that encodes the non-speech signal; and

the multiplexer includes a selector/multiplexer circuit that selects the encoded speech signal, the encoded non-speech signal, or the identifying signal in response to the selection signal.

66. The apparatus of claim 58 including:

a transmitter that transmits intermingled encoded speech and non-speech signals selected by the multiplexer along with the identifying signal; and

a receiver that receives the transmitted encoded speech and non-speech signals and restores the encoded speech and non-speech signals into a reassembled audio signal corresponding to the digital audio information, for audible presentation.

67. The apparatus of claim 66 wherein the receiver includes:

a memory that stores transmitted signals;

an identification signal decoder coupled to the memory that separates the identifying signal from the encoded speech and non-speech signals;

a decoder coupled to receive the encoded speech and non-speech signals that separately decodes each of the encoded speech and non-speech signals; and

a switch coupled to receive the decoded speech and non-speech signals that selects the decoded speech or the non-speech signal in response to the separated identifying signal to form the reassembled audio signal for audible presentation.

68. Method of decoding digital audio information formed of speech signals and non-speech signals, the audio information including a signal identifying the speech and non-speech signals, the steps including:

receiving combined speech and non-speech signals and the identifying signal;

separating the identifying signal from the speech and non-speech signals; and

intermingling the speech and non-speech signals into a reassembled audio signal in response to the identifying signal, for audible presentation of the reassembled audio.

69. The method of claim 68 wherein the step of separating further includes the step:

detecting the identifying signal and extracting it from the combined signals.

70. The method of claim 68 wherein the step of receiving further includes the step:

storing the combined speech, non-speech, and identifying signals; and

retrieving the stored signals.

71. Apparatus for decoding digital audio information formed of signals such as speech signals and non-speech signals, the audio information including a signal identifying the speech and non-speech signals, comprising:

a receiver that receives combined speech, non-speech and identifying signals;

an identification signal decoder coupled to receive the combined speech, non-speech and identifying signals which separates the identifying signal; and

a switch coupled to receive the speech and non-speech signals that reassembles the speech and non-speech signals in response to the identifying signal into an audio signal, for audible presentation.

72. The apparatus of claim 71 wherein the identification signal decoder further includes:

an extractor that detects the identifying signal and extracts it from the combined speech, non-speech and identifying signals.

73. The apparatus of claim 71 wherein the receiver further includes:

a storage circuit coupled to receive the combined speech, non-speech, and identifying signals for storing the combined speech, non-speech, and identifying signals; and

a retriever circuit for retrieving the stored signals.

74. Apparatus for encoding digital audio information formed of audio signals such as speech signals and music signals, comprising:

a generator which provides a selection signal indicative of the speech signal and the music signal;

a circuit responsive to the selection signal that provides an identification signal indicative of the audio signals for inclusion with selected audio signals; and

a multiplexer coupled to receive the speech signal, the music signal, and the identification signal that intermingles the speech signal, the music signal and the identification signal in response to the selection signal.

75. The apparatus of claim 74 wherein the generator includes:

a detector that detects whether the information is a speech signal or a music signal; and

the generator being responsive to the detector.

76. The apparatus of claim 75 wherein the detector includes:

a first circuit that generates a first signal indicative of a speech signal;

a second circuit that generates a second signal indicative of a music signal; and

a logic coupled to receive the first and second signals that generates the selection signal in response to the first and second signals.

77. The apparatus of claim 76 wherein the first signal is representative of a preselected ratio of pauses in the audio information to indicate the speech signal.

78. The apparatus of claim 76 where the first circuit includes:

a filter that passes a passband signal in a frequency range which contains the maximum speech energy; and

a pause detector responsive to the filter that generates the first signal indicative of an occurrence of successive pauses in the audio information.

79. The apparatus of claim 76 wherein the second circuit includes:

a third circuit responsive to a passband signal in a frequency range which contains the maximum speech energy and the audio information that provides a third signal representing a level of frequency components outside the range of the speech signal; and

a logic responsive to the third signal and to a predetermined threshold level for producing the second signal indicative of the level of energy in the third signal.

80. The apparatus of claim 79 wherein the logic further includes an audio level threshold circuit that compares the third signal with the predetermined threshold level.

81. The apparatus of claim 76 wherein the generator further includes AND logic responsive to logic states of the first signal and the second signal for generating the selection signal.

82. The apparatus of claim 74 further including a voice encoder that encodes the speech signal;

wherein the voice encoder is selected by the multiplexer where the selection signal indicates a speech signal.

83. The apparatus of claim 74 further including a wide-band audio compression encoder that encodes the music signal;

wherein the wide-band encoder is selected by the multiplexer where the selection signal indicates a music signal.

84. The apparatus of claim 74 further including:

a voice encoder that encodes the speech signal;

a wide-band audio compression encoder that encodes the music signal.

85. The apparatus of claim 74 wherein the circuit responsive to the selection signal includes:

a timing generator that synchronizes the identification signal with the occurrence of the speech and music signals; and

a latch responsive to the timing generator that provides the identification signal.

86. The apparatus of claim 85 wherein the audio signals include an ASCII text signal, including:

a buffer that selectively supplies the ASCII text signal to the multiplexer; and

the timing generator is responsive to a buffer for storing the speech and music signals in response to the buffer supplying the ASCII text signal.

87. The apparatus of claim 74 wherein the detector means includes:

a voice encoder that receives and compresses the audio signals;

a comparator that compares the accuracy of reconstructed voice coded signals generated from the compressed audio signals with the audio signals; and

a generator that generates the selection signal indicative of a speech signal in response to an accurate comparison between the reconstructed audio signals and the audio signals and that generates the selection signal indicative of a music signal in response to a significant inaccuracy in the comparison.

88. The apparatus of claim 87 wherein the comparator includes a threshold circuit.

89. Method for encoding digital audio information formed of audio signals including speech signals and music signals, comprising the steps:

generating a selection signal indicative of the speech signal and the music signal;

providing an identification signal indicative of the audio signals for inclusion with selected audio signals in response to the selection signal; and

intermingling the speech signal, the music signal, and the identification signal in response to the selection signal.

90. The method of claim 89 wherein the generating step further includes the step of:

detecting whether the audio information is a speech signal or a music signal.

91. The method of claim 90 wherein the generating step further includes the steps of:

generating a first signal indicative of the speech signal;

generating a second signal indicative of the music signal; and

generating the selection signal in response to the first and second signals.

92. The method of claim 91 wherein the step of generating the first signal further includes the steps of:

filtering out signals except a passband signal in a frequency range which contains maximum speech energy;

detecting pauses in the passband signal; and

generating the first signal indicative of speech where there is an occurrence of successive pauses in the audio information.

93. The method of claim 91 wherein the step of generating the second signal further includes the steps of:

providing a third signal responsive to a passband signal in a frequency range that contains maximum speech energy and the audio information representing a level of frequency components outside the range of the speech signal; and

generating a second signal responsive to the third signal indicative of the music signal.

94. The method of claim 93 wherein the step of generating a second signal further includes the steps of:

comparing the third signal with a predetermined threshold level; and

generating the second signal as indicating music where the third signal exceeds the predetermined threshold level.

95. The method of claim 91 wherein the step of generating a selection signal further includes the steps of:

generating a selection signal indicative of music where the second signal indicates music;

or

generating a selection signal indicative of speech where the first signal indicates speech and the second signal does not indicate music.

96. The method of claim 89 further includes the steps of:

voice encoding the speech signal; and

wide-band compression encoding the music signal.

97. The method of claim 96 wherein the step of intermingling further includes:

selecting the voice encoded signal when the selection signal indicates the speech signal;

or

selecting the wide-band compression encoded signal when the selection signal indicates the music signal.

98. The method of claim 89 further includes the steps of:

voice encoding the speech signal;

wide-band compression encoding the music signal; and

intermingling the encoded speech signal, the encoded music signal, and the identification signal in response to the selection signal.

99. The method of claim 89 further includes the steps of:

generating a timing signal responsive to the selection signal for synchronizing the identification signal with the speech and music signals; and

synchronizing the identification signal with the speech and music signals by use of a latch responsive to the timing signal.

100. The method of claim 99, wherein the speech and music signals include an ASCII text signal, and further including the steps:

storing the ASCII text signal in a buffer;

storing the speech and music signals when the ASCII text is supplied for use in the intermingling step; and

supplying the speech and music signals for use in the intermingling step after the ASCII text has been supplied.

101. The method of claim 89 further includes the steps of:

voice encoding the audio signals;

reconstructing audio signals from the voice encoded audio signals;

comparing the accuracy of the reconstructed audio signals with the audio signals;

generating a selection signal indicative of a speech signal in response to an accurate reproduction of the audio signals;

or

generating a selection signal indicative of a music signal in response to an inaccurate reproduction of the audio signals.

102. The method of claim 101 wherein the step of comparing further includes the step of comparing the difference between the reconstructed audio signal and the audio signal with a selected threshold level.

103. Apparatus for decoding digital audio information formed of signals such as speech signals and music signals, the audio information including a signal identifying the speech and music signals, comprising:

a receiver that receives combined speech, music, and identifying signals;

an identification signal decoder coupled to receive the combined speech, music and identifying signals which separates the identifying signal; and

a switch coupled to receive the speech and music signals that reassembles the speech and music signals in response to the identifying signal into an audio signal, for audible presentation.

104. The apparatus of claim 103 wherein the identification signal decoder further includes:

an extractor that detects the identifying signal and extracts it from the combined speech, music and identifying signals.

105. The apparatus of claim 103 wherein the receiver further includes:

a storage circuit coupled to receive the combined speech, music, and identifying signals for storing the combined speech, music, and identifying signals; and

a retriever circuit for retrieving the stored signals.

106. Method of decoding digital audio information formed of speech signals and music signals, the audio information including a signal identifying the speech and music signals, the steps including:

receiving combined speech and music signals and the identifying signal;

separating the identifying signal from the speech and music signals; and

intermingling the speech and music signals into a reassembled audio signal in response to the identifying signal, for audible presentation of the reassembled audio.

107. The method of claim 106 wherein the step of separating further includes the step of detecting the identifying signal and extracting it from the combined signals.

108. The method of claim 106 wherein the step of receiving further includes the step of storing the combined speech, music, and identifying signals;

and retrieving the stored signals.