Method for transcoding audio signals, transcoder, network element, wireless communications network and communications system

• US 20040254786A1
• Filed: 01/14/2004
• Published: 12/16/2004
• Est. Priority Date: 06/26/2001
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Corporation
• Inventors: Kirla, Olli, Himanen, Teemu, Lepanaho, Henrik
• Granted Patent: US 7,343,282 B2
• Time in Patent Office: Days
• US Class Current: 704/216
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: H04W 88/181 Transcoding devices; Rate adaptation devices

Abstract

The invention relates to a method for transcoding audio signals in a communications system. In order to improve the inter-operability between units (2,40) capable of handling wideband audio signals and units (3,46) or network components (50) capable of handling narrowband audio signals, it is proposed that first, an audio signal is received in a network element (42) of a communications network via which said audio signal is transmitted. Next, it is determined in said network element (42) whether a transcoding of the received audio signal is required. In case a narrowband-to-wideband transcoding of the received signal is required, the received narrowband audio signal is transcoded into a wideband audio signal in the network element (1,42). The generated wideband audio signal is then forwarded to the receiving terminal (2,40). The invention equally relates to a corresponding communications system and its components.

Claims

1-34. -34. (Cancelled).

35. Method for transcoding an audio signal in a communications system, which audio signal is to be transmitted to a receiving unit via a communications network, said method comprising:

receiving an audio signal in a network element of said communications network;

determining in said network element based at least on the kind of the received signal and on the capabilities of said receiving unit whether a transcoding of the received audio signal is required;

in case said received audio signal is a narrowband audio signal and in case it was determined that a narrowband-to-wideband transcoding of the received signal is required, converting said received narrowband audio signal into a wideband audio signal in said network element, and forwarding the generated wideband audio signal to the receiving unit.

36. Method according to claim 35, wherein said network determines whether a transcoding of the received audio signal is required in addition based on the capabilities of an interconnect network interconnecting said network element with said receiving unit.

37. Method according to claim 35, wherein said receiving unit is a wideband terminal, a narrowband terminal or a speech-based network service equipment.

38. Method according to claim 35, wherein a received narrowband audio signal is converted into a wideband audio signal in said network element by generating an at least partially artificial wideband audio signal based on the received narrowband audio signal.

39. Method according to claim 35, wherein said received audio signal is an encoded audio signal, wherein a received narrowband audio signal is decoded before being converted to a wideband audio signal, and wherein a generated wideband audio signal is encoded before being forwarded to the receiving unit.

40. Method according to claim 35, wherein converting a received narrowband signal comprises up-sampling the received narrowband audio signal and frequency shaping the up-sampled signal in a way suited to smooth distortions resulting in the up-sampling.

41. Method according to claim 35, wherein converting a received narrowband audio signal comprises

up-sampling the received narrowband audio signal and lowpass filtering the up-sampled signal in order to obtain a lower band signal;

generating an artificial upper band signal based on a statistical evaluation of the received narrowband audio signal; and

combining the obtained lower band signal with the generated upper band signal to a wideband audio signal.

42. Method according to claim 41, wherein the artificial upper band signal is generated by performing a spectral analysis of a received narrowband audio signal and by mapping resulting narrowband codebook values to wideband codebook values, the wideband codebook values forming a spectrum-shaping filter used for shaping upper band excitation signal.

43. Method according to claim 35, wherein said received audio signal is an encoded audio signal, and wherein a received narrowband audio signal is converted without decoding to a coded wideband audio signal in the speech parameter domain.

44. Method according to claim 35, further comprising in case said received audio signal is a wideband audio signal and in case it was determined that a wideband-to-narrowband transcoding of the received signal is required, converting said received wideband audio signal into a narrowband audio signal, and transmitting the generated narrowband audio signal to the receiving unit.

45. Method according to claim 44, wherein said received audio signal is an encoded audio signal, wherein a received wideband audio signal is decoded before being converted to a narrowband audio signal, and wherein a generated narrowband audio signal is encoded before being forwarded to the receiving unit.

46. Method according to claim 44, wherein said received audio signal is an encoded audio signal, and wherein a received wideband audio signal is converted without decoding to a coded narrowband audio signal in the speech parameter domain.

47. Method according to claim 35, wherein said network element is a network element of a wireless communications network.

48. Method according to claim 35, wherein a receiving unit is capable of handling wideband audio signals, wherein a narrowband audio signal is transmitted by a public switched telephone network terminal capable of handling narrowband audio signals and addressed to said receiving unit, wherein said narrowband audio signal is transmitted via said communications network to said receiving unit, and wherein said narrowband audio signal is converted in a network element of said communications network to an at least partially artificial wideband audio signal before transmission to said receiving unit.

49. Method according to claim 35, wherein a receiving unit is capable of handling wideband audio signals, wherein said communications network comprises a wireless communications network to which said receiving unit is connected, wherein a narrowband audio signal is transmitted by a unit capable of handling narrowband audio signals and addressed to said receiving unit, wherein said narrowband audio signal is transmitted via said wireless communications network to said receiving unit, and wherein said narrowband audio signal is converted in a network element of said wireless communications network to an at least partially artificial wideband audio signal for transmission to said receiving unit.

50. Method according to claim 35, wherein a receiving unit is capable of handling narrowband audio signals, wherein a wideband audio signal is transmitted by a transmitting unit capable of handling wideband audio signals and addressed to said receiving unit, wherein said communications network comprises a wireless communications network to which said transmitting unit is connected, wherein said wideband audio signal is to be transmitted via said wireless communications network to said receiving unit, and wherein said wideband audio signal is converted in a network element of said wireless communications network to a narrowband audio signal for transmission to said receiving unit.

51. Method according to claim 35, wherein a receiving unit is capable of handling wideband audio signals, wherein said communications network comprises a first wireless communications network to which said receiving unit is connected, wherein a wideband audio signal is transmitted by a transmitting unit capable of handling wideband audio signals and addressed to said receiving unit, wherein said communications network comprises a further wireless communications network to which said transmitting unit is connected, wherein said first and said further wireless communications network are interconnected by an interconnect network capable of transmitting narrowband audio signals, wherein said wideband audio signal transmitted by said transmitting unit is converted in a network element of said further wireless communications network into a narrowband audio signal for transmission to said first wireless communications network via said interconnect network, and wherein said narrowband signal is converted in a network element of said first wireless communications network to an at least partially artificial wideband audio signal for transmission to said receiving unit.

52. Network element for a communications network comprising:

means for receiving audio signals addressed at a receiving unit;

processing means for determining whether a transcoding of the received audio signal is required based at least on the kind of the received audio signal and on the capabilities of the receiving unit;

transcoder for transcoding a received audio signal, said transcoder comprising means for converting a received narrowband audio signal into a wideband audio signal, in case said transcoder receives an indication from within said network element that a narrowband-to-wideband transcoding of a received signal is required; and

means for forwarding audio signals to a receiving unit.

53. Network element according to claim 52, wherein said processing means determine whether a transcoding of the received audio signal is required based in addition on the capabilities of an interconnect network interconnecting said network element and said receiving unit.

54. Network element according to claim 52, wherein said means of said transcoder for converting a received narrowband audio signal into a wideband audio signal are means for converting said received narrowband audio signal into a wideband audio signal by generating an at least partially artificial wideband audio signal based on the received narrowband audio signal.

55. Network element according to claim 52, wherein said transcoder further comprises decoding means for decoding a received narrowband audio signal before it is converted by the means for converting, and encoding means for encoding a generated wideband audio signal to an encoded wideband audio signal.

56. Network element according to claim 52, wherein said means for converting of said transcoder comprise means for up-sampling a received narrowband audio signal and means for frequency shaping said up-sampled signal in a way suited to smooth distortions resulting in the up-sampling.

57. Network element according to claim 52, wherein said means of said transcoder for converting comprise

means for up-sampling a received narrowband audio signal and for lowpass filtering the up-sampled signal in order to obtain a lower band signal;

means for generating an artificial upper band signal based on a statistical evaluation of the received narrowband audio signal; and

means for combining the obtained lower band signal with the generated upper band signal to a wideband audio signal.

58. Network element according to claim 57, wherein said means of said transcoder for generating an artificial upper band signal comprise a spectral analyzer for analyzing a received narrowband signal, and means for spectrum-shaping the analyzed signals with a filter for shaping upper band excitation, wherein said filter is created by mapping narrowband codebook values obtained based on the spectral analysis to wideband codebook values.

59. Network element according to claim 52, wherein said means of said transcoder for converting a received narrowband audio signal into a wideband audio signal are means for converting a received encoded narrowband signal into an encoded wideband signal in the parameter domain.

60. Network element according to claim 52, wherein said transcoder further comprises means for converting a received wideband audio signal into a narrowband audio signal in case said transcoder receives information from within said network element that a wideband-to-narrowband transcoding of a received signal is required.

61. Network element according to claim 60, wherein said transcoder further comprises decoding means for decoding a received wideband audio signal before it is converted by the means for converting, and encoding means for encoding a generated narrowband audio signal to an encoded narrowband audio signal.

62. Network element according to claim 60, wherein said means of said transcoder for converting a received wideband audio signal into a narrowband audio signal are designed for converting a received encoded wideband signal into an encoded narrowband signal in the parameter domain.

63. Wireless communications network comprising a network element according to claim 52.

64. Communications system comprising a first unit capable of handling narrowband audio signals, a second unit capable of handling wideband audio signals, and a communications network with a network element according to claim 52, said first unit being interconnectable with said second unit via said communications network.

65. Communications system according to claim 64, wherein said first unit capable of handling narrowband audio signals is a public switched telephone network terminal capable of handling narrowband audio signals.

66. Communications system according to claim 64, wherein said first unit capable of handling narrowband audio signals is a narrowband terminal accessing a first wireless communications network, wherein said second unit capable of handling wideband audio signals is a wideband terminal accessing a second wireless communications network, wherein said first unit is interconnected with said second unit via said first wireless communications network, an interconnect network and said second wireless communications network, and wherein said network element is part of said second wireless communications network.

67. Communications system according to claim 64, wherein said first unit capable of handling narrowband audio signals is a narrowband speech-based network service equipment connected to an interconnect network, wherein said second unit capable of handling wideband audio signals is a wideband terminal accessing a wireless communications network, wherein said first unit is interconnected with said second unit via said interconnect network and said wireless communications network, and wherein said network element is part of said wireless communications network.

68. Communications system comprising a first unit capable of transmitting wideband audio signals, a second unit capable of receiving and handling wideband audio signals, and a communications network comprising at least a first wireless communications network, an interconnect network capable of handling narrowband audio signals, and a second wireless communications network, wherein said first unit is interconnectable with said second unit via said first wireless communications network, said interconnect network, and said second wireless communications network, each wireless communications network comprising a network element according to claim 52.