Dynamic vocoder selection for storing and forwarding voice signals

• US 6,363,339 B1
• Filed: 10/10/1997
• Issued: 03/26/2002
• Est. Priority Date: 10/10/1997
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Rabipour, Rafi, Patel, Girish
• Primary Examiner(s): Smits, Talivaldis Ivars
• Application Number:
  US08/948,315
• Time in Patent Office: 1,628 Days
• Field of Search: 704/201, 704/219, 704/226, 379/68, 379/88.16
• US Class Current: 704/201
• CPC Class Codes: H04M 2207/18 wireless networks
• CPC Class Codes: H04M 2207/20 hybrid systems
• CPC Class Codes: H04M 3/533 Voice mail systems
• CPC Class Codes: H04M 7/12 for working between exchanges having different types of switching equipment, e.g. power-driven and step by step or decimal and non-decimal
• CPC Class Codes: H04W 88/181 Transcoding devices; Rate adaptation devices

Abstract

In recent years, the telecommunications industry has witnessed the proliferation of a variety of digital vocoders in order to meet bandwidth demands of different wireline and wireless communication systems. The rapid growth in the diversity of networks and the number of users of such networks is increasing the number of instances where two vocoders are placed in tandem to serve a single connection. Such arrangements of low bit-rate codecs can degrade the quality of the transmitted speech. To overcome this problem in the specific situation involving store-and-forward systems (e.g. voicemail), the invention provides a novel method and apparatus including a plurality of different vocoders that can be selectively invoked to process the voice signal so as to reduce signal degradation. Also, the apparatus has the capability to bypass the vocoder bank when exchanging data with a remote signal processor capable of accepting data frames in compressed format.

Claims

1. A voice storage and forwarding device, comprising:

an input for receiving a digital signal that conveys audio information;

a group of vocoders, each vocoder including an encoder stage capable of compressing the digital signal that conveys audio information in at least one data frame;

a switch capable of acquiring a plurality of vocoder selection positions, in each vocoder selection position said switch directing the digital signal that conveys audio information received at said input to a selected one of said vocoders of said group of vocoders;

a tagging unit capable of generating a vocoder type designator for association with a data frame issued by the encoder stage of a given vocoder of said group of vocoders, said vocoder type designator capable of uniquely identifying the given vocoder amongst the vocoders in said group of vocoders;

a storage medium in a data communicative relationship with said vocoders, said storage medium capable to store data that conveys audio information issued by a vocoder from said group of vocoders and transmit stored data that conveys audio information toward a selected one of said vocoders.

2. A voice storage and forwarding device as defined in claim 1, wherein the encoder stage of each vocoder is capable of compressing the audio information in at least one data frame of a format different from a format of a data frame issued by any other vocoder of said group of vocoders.

3. A voice storage and forwarding device as defined in claim 1, wherein each vocoder includes an encoder stage capable of compressing the digital signal that conveys audio information in at least one data frame including an excitation segment and a coefficients segment.

4. A voice storage and forwarding device as defined in claim 1, wherein said storage medium is capable of forwarding a data frame stored on said storage medium to a selected vocoder from said group of vocoders.

5. A voice storage and forwarding device as defined in claim 4, wherein said switch is responsive to a vocoder type designator associated to a data frame stored on said storage medium to acquire a vocoder selector position to select a vocoder in said group of vocoders to which the data frame stored on said storage medium will be forwarded.

6. A voice storage and forwarding device as defined in claim 5, wherein each vocoder from said group of vocoders includes a decoder stage, a data frame issued by said storage medium and forwarded to the decoder stage of a selected vocoder being decompressed by the decoder stage of the selected vocoder.

7. A voice storage and forwarding device as defined in claim 1, wherein said switch is responsive to control information generated in a course of a given message recording transaction, to acquire a vocoder selector position indicated by the control information.

8. A voice storage and forwarding device as defined in claim 1, wherein said switch is capable of acquiring a bypass operative position, in said bypass operative position, said switch transferring a data frame including an excitation segment and a coefficients segment impressed at said input to said storage medium for storage of the data frame thereon.

9. A voice storage and forwarding device as defined in claim 8, wherein said switch is capable acquiring either one of a vocoder selector position and said bypass position in dependence of control data forwarded at said input.

10. A communication system, comprising:

a database storing a plurality of vocoder type identifiers;

a voice storage and forwarding device;

a data transmission pathway between said database and said voice storage and forwarding device, said voice storage and forwarding device including;

a) an input for receiving a digital signal that conveys audio information;

b) a group of vocoders, each vocoder including an encoder stage capable of compressing the digital signal that conveys audio information in at least one data frame;

c) a switch capable of acquiring a plurality of vocoder selection positions, in each vocoder selection position said switch directing the digital signal that conveys audio information received at said input to a selected one of said vocoders of said group of vocoders, said switch being responsive to a vocoder type identifier received from said database over said data transmission pathway to acquire a vocoder selection position;

d) a tagging unit capable of generating a vocoder type designator for association with a data frame issued by the encoder stage of a given vocoder of said group of vocoders, said vocoder type designator capable of uniquely identifying the given vocoder amongst the vocoders in said group of vocoders;

e) a storage medium in a data communicative relationship with said vocoders, said storage medium capable to store data that conveys audio information issued by a vocoder from said group of vocoders and transmit stored data that conveys audio information toward a selected one of said vocoders.

11. A communication system as defined in claim 10, wherein each vocoder includes an encoder stage capable of compressing the digital signal that conveys audio information in at least one data frame including an excitation segment and a coefficients segment.

12. A communication system as defined in claim 11, wherein the encoder stage of each vocoder is capable of compressing the audio information in at least one data frame of a format different from a format of a data frame issued by any other vocoder of said group of vocoders.

13. A communication system as defined in claim 10, wherein said storage medium is capable of forwarding a data frame stored on said storage medium to a selected vocoder from said group of vocoders.

14. A communication system as defined in claim 13, wherein said switch is responsive to a vocoder type designator associated to a data frame stored on said storage medium to acquire a vocoder selector position to select a vocoder in said group of vocoders to which the data frame stored on said storage medium will be forwarded.

15. A communication system as defined in claim 14, wherein each vocoder from said group of vocoders includes a decoder stage, a data frame issued by said storage medium and forwarded to the decoder stage of a selected vocoder being decompressed by the decoder stage of the selected vocoder.

16. A communication system as defined in claim 10, wherein said switch is capable of acquiring a bypass operative position, in said bypass operative position, said switch transferring a data frame including an excitation segment and a coefficients segment impressed at said input to said storage medium for storage of the data frame thereon.

17. A communication system as defined in claim 16, wherein said switch is capable acquiring either one of a vocoder selector position and said bypass position in dependence of control data forwarded at said input.

18. A voice storage and forwarding device, comprising:

an input for receiving an audio data signal that conveys speech sound information, the audio data signal being in either one of a first format and a second format;

at least one vocoder;

a switch capable of acquiring at least two operative positions, namely a vocoder selection position and a bypass position, in said vocoder selection position said switch directing the audio data signal received at said input in the first format to said vocoder for conversion of the audio data signal from the first format to the second format;

a storage medium in a data communicative relationship with said vocoder and with said switch, said storage medium capable to store audio data signals in the second format issued by said vocoder and transmit stored audio data signals in the second format toward said vocoder;

in said bypass position said switch bypassing said vocoder and directing the audio data signal received at said input in the second format toward said storage medium.

19. A voice storage and forwarding device as defined in claim 18, wherein said switch is responsive to a control message received at said input to acquire said bypass position.

20. A voice storage and forwarding device as defined in claim 19, wherein said control message is transmitted via inband signaling.

21. A voice storage and forwarding device as defined in claim 20, wherein said control message includes a portion identifying a source of said control message.

22. A voice storage and forwarding device as defined in claim 21, wherein said switch is capable of issuing via in-band signaling in response to said control message an acknowledgement message.

23. A voice storage and forwarding device as defined in claim 22, wherein said acknowledgement message includes a portion identifying said switch.

24. A voice storage and forwarding device as defined in claim 21, wherein said switch in the absence of control message assumes said vocoder selector position.

25. A voice storage and forwarding device as defined in claim 19, wherein said voice and forwarding device comprises:

a group of vocoders;

a switch capable of acquiring a plurality of vocoder selection positions, in each vocoder selection position said switch directing the digital signal that conveys audio information received at said input to a selected one of said vocoders of said group of vocoders.

26. A voice storage and forwarding device as defined in claim 25, wherein each vocoder includes an encoder stage capable of compressing the digital signal that conveys audio information in at least one data frame including an excitation segment and a coefficients segment.

27. A voice storage and forwarding device as defined in claim 26, wherein the encoder stage of each vocoder is capable of compressing the audio information in at least one data frame of a format different from a format of a data frame issued by any other vocoder of said group of vocoders.

28. A voice storage and forwarding device as defined in claim 25, comprising a tagging means capable of generating a vocoder type designate or for association with a data frame issued by the encoder stage of a given vocoder of said group of vocoders, said vocoder type designator capable of uniquely identifying the given vocoder amongst the vocoders in said group of vocoders.

29. A voice storage and forwarding device as defined in claim 28, wherein said storage medium is capable of forwarding a data frame stored on said storage medium to a selected vocoder from said group of vocoders.

30. A voice storage and forwarding device as defined in claim 29, wherein said switch is responsive to a vocoder type designator associated to a data frame stored on said storage medium to acquire a vocoder selector position to select a vocoder in said group of vocoders to which the data frame stored on said storage medium will be forwarded.

31. A voice storage and forwarding device as defined in claim 30, wherein each vocoder from said group of vocoders includes a decoder stage, a data frame issued by said storage medium and forwarded to the decoder stage of a selected vocoder being decompressed by the decoder stage of the selected vocoder.

32. A voice storage and forwarding device as defined in claim 31, wherein said switch is responsive to control information generated in a course of a given message recording transaction, to acquire a vocoder selector position indicated by the control information.

33. A voice storage and forwarding device as defined in claim 18, wherein said second format is a compressed version of the audio data signal in the first format.

34. A voice storage and forwarding device as defined in claim 18, wherein said second format is an encoded version of the audio data signal in the first format.

35. A voice storage and forwarding device as defined in claim 18, wherein when in said first format, the audio data signal is in PCM format.

36. A communication system, comprising:

a base station or base station controller including a digital signal processor;

a voice storage and forwarding device;

a data transmission pathway between said base station and said voice storage and forwarding device, said voice storage and forwarding device including;

a) an input for receiving an audio data signal that conveys speech sound information, the audio data signal being in either one of a first format and a second format;

b) at least one vocoder;

c) a switch capable of acquiring at least two operative positions, namely a vocoder selection position and a bypass position, in said vocoder selection position said switch directing the audio data signal received at said input in the first format to said vocoder for conversion of the audio data signal from the first format to the second format;

d) a storage medium in a data communicative relationship with said vocoder and with said switch, said storage medium capable to store audio data signals in the second format issued by said vocoder and transmit stored audio data signals in the second format toward said vocoder;

e) in said bypass position said switch bypassing said vocoder and directing the audio data signal received at said input in the second format toward said storage medium;

f) said switch operative to acquire said bypass position in response to a control message received from said digital signal processor over said data transmission pathway.

37. A communication system as defined in claim 36, wherein said control message includes a portion identifying said digital signal processor.

38. A communication system as defined in claim 37, wherein said switch is capable of issuing via inband signaling in response to said control message an acknowledgement message.

39. A communication system as defined in claim 38, wherein said acknowledgement message includes a portion identifying said switch.

40. A communication system as defined in claim 39, wherein said switch in the absence of control message assumes said vocoder selector position.

41. A communication system as defined in claim 36, wherein said second format is a compressed version of the audio data signal in the first format.

42. A communication system as defined in claim 36, wherein said second format is an encoded version of the audio data signal in the first format.

43. A communication system as defined in claim 36, wherein when in said first format, the audio data signal is in PCM format.

44. A method for storing audio data containing speech sound information, the audio data being in either one of a first format and a second format, said method comprising the steps of:

providing a vocoder;

providing a switch capable of acquiring either one of a vocoder selection position and a bypass position, in said vocoder selection position said switch directing audio data in the first format to said vocoder for conversion of the audio data from the first format to a second format;

providing a storage medium in a data communicative relationship with said vocoder, said storage medium capable to store audio data in the second format issued by said vocoder;

in said bypass position said switch bypassing said vocoder and directing audio data in the second format toward said storage medium;

setting said switch to a selected one of the vocoder selection position and the bypass position to permit transfer of audio data to said storage device.

45. A method as defined in claim 44, comprising the step of setting said switch to said bypass position in response of reception by said switch of a control message.

46. A method as defined in claim 45, wherein said control message is transmitted to said switch by in-band signaling.

47. A method as defined in claim 46, wherein said control message includes a portion identifying a source of said message.

48. A method as defined in claim 47, comprises the step of issuing an acknowledgement message in response to said control message.