Signal processing system for filtering spectral content of a signal for speech coding
First Claim
1. A method for conditioning a speech signal in preparation for coding of the speech signal, the method comprising the steps of:
- accumulating samples of the speech signal over at least a minimum sampling duration;
evaluating the accumulated samples associated with the minimum sampling period to obtain a representative sample;
determining whether a slope of the representative sample of the speech signal conforms to a defined characteristic slope stored in a reference database of spectral characteristics; and
selecting one of a first filter and a second filter for application to the speech signal prior to the coding;
wherein the selecting step selects the first filter if the determining step determines that the slope of the representative sample of the speech signal conforms to the defined characteristic slope, and wherein the selecting step selects the second filter if the determining step determines that the slope of the representative sample of the speech signal is generally flat.
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Abstract
A signal processing system is well suited for conditioning a speech signal prior to coding the speech signal to achieve enhanced perceptual quality of reproduced speech. The signal processing system may be incorporated into mobile or portable wireless communications devices, wireless infrastructure equipment, or both. The signal processing system includes a filtering arrangement for filtering an input speech signal to make a spectral response of the speech signal more uniform to compensate for spectral variations that might otherwise be imparted into the speech signal by a communications network associated with the signal processing system.
43 Citations
34 Claims
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1. A method for conditioning a speech signal in preparation for coding of the speech signal, the method comprising the steps of:
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accumulating samples of the speech signal over at least a minimum sampling duration;
evaluating the accumulated samples associated with the minimum sampling period to obtain a representative sample;
determining whether a slope of the representative sample of the speech signal conforms to a defined characteristic slope stored in a reference database of spectral characteristics; and
selecting one of a first filter and a second filter for application to the speech signal prior to the coding;
wherein the selecting step selects the first filter if the determining step determines that the slope of the representative sample of the speech signal conforms to the defined characteristic slope, and wherein the selecting step selects the second filter if the determining step determines that the slope of the representative sample of the speech signal is generally flat. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A system for conditioning a speech signal prior to coding the speech signal, the system comprising:
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a buffer memory for accumulating samples of the speech signal over at least a minimum sampling duration;
an averaging unit for evaluating the accumulated samples associated with the minimum sampling period to obtain a representative sample;
a storage device adapted to store spectral characteristics for classifying the speech signal as a closest one of a defined characteristic slope and a flat speech signal;
an evaluator adapted to determine whether a slope of the representative sample of the speech signal conforms to a defined characteristic slope stored in the storage device; and
a selector for selecting a preferential one of a first filter and a second filter for application to the speech signal prior to the coding;
wherein the selector selects the first filter if the evaluator determines that the slope of the representative sample of the speech signal conforms to the defined characteristic slope, and wherein the selector selects the second filter if the evaluator determines that the slope of the representative sample of the speech signal is generally flat. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34)
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Specification