Methods for generating comfort noise during discontinuous transmission
First Claim
1. A method for producing comfort noise (CN) in a digital mobile terminal that uses a discontinuous transmission, comprising the steps of:
- in response to a speech pause, calculating random excitation spectral control (RESC) parameters;
transmitting the RESC parameters to a receiver together with predetermined ones of CN parameters;
receiving the RESC parameters; and
shaping the spectral content of an excitation using the received RESC parameters prior to applying the excitation to a synthesis filter.
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Abstract
An improved method for generating comfort noise (CN) in a mobile terminal operating in a discontinuous transmission (DTX) mode. In one embodiment the invention provides an improved method for comfort noise generation, in which a random excitation is modified by a spectral control filter so that the frequency content of comfort noise and background noise become similar. In another embodiment the transmitter identifies speech coding parameters that are not representative of the actual background noise, and replaces the identified parameters with parameters having a median value. In this manner the non-representative parameters do not skew the result of an averaging operation.
142 Citations
56 Claims
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1. A method for producing comfort noise (CN) in a digital mobile terminal that uses a discontinuous transmission, comprising the steps of:
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in response to a speech pause, calculating random excitation spectral control (RESC) parameters; transmitting the RESC parameters to a receiver together with predetermined ones of CN parameters; receiving the RESC parameters; and shaping the spectral content of an excitation using the received RESC parameters prior to applying the excitation to a synthesis filter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. Apparatus for generating comfort noise (CN) in a system having a digital mobile terminal that uses a discontinuous transmission to a network, comprising:
- means in said digital mobile terminal that is responsive to a speech pause for calculating random excitation spectral control (RESC) parameters and for transmitting the RESC parameters together with predetermined ones of CN parameters to a receiver in said network; and
means in said network for shaping the spectral content of an excitation using received RESC parameters prior to applying the excitation to a synthesis filter. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
- means in said digital mobile terminal that is responsive to a speech pause for calculating random excitation spectral control (RESC) parameters and for transmitting the RESC parameters together with predetermined ones of CN parameters to a receiver in said network; and
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31. A method for generating comfort noise (CN) in a digital mobile terminal that uses a discontinuous transmission, comprising the steps of:
- in response to a speech pause, buffering a set of speech coding parameters;
within an averaging period, replacing speech coding parameters of the set that are not representative of background noise with speech coding parameters that are representative of the background noise; and averaging the set of speech coding parameters. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
- in response to a speech pause, buffering a set of speech coding parameters;
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51. Apparatus for generating comfort noise (CN) in a system having a digital mobile terminal that uses a discontinuous transmission to a network, comprising:
data processing means in said digital mobile terminal that is responsive to a speech pause for buffering a set of speech coding parameters and, within an averaging period, for replacing speech coding parameters of the set that are not representative of background noise with speech coding parameters that are representative of the background noise, said data processing means averaging the set of speech coding parameters and transmitting the averaged set of speech coding parameters to the network. - View Dependent Claims (52, 53, 54, 55)
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56. A method for producing comfort noise (CN), comprising the steps of:
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in response to a speech pause, transmitting CN parameters to a receiver; and shaping the spectral content of an excitation by steps of, forming an excitation from a white noise excitation sequence; scaling the white noise excitation sequence to produce a scaled white noise excitation sequence; and processing the scaled white noise excitation sequence in a synthesis filter having fixed coefficients that are optimized to provide at least one of a desired comfort noise quality or to cause the frequency response of the synthesis filter to resemble that of a random excitation spectral control (RESC) filter having transmitted coefficients.
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Specification