Mode-specific method and apparatus for encoding signals containing speech
DCFirst Claim
1. A method of encoding a signal having a speech component, the signal being organized as a plurality of frames, the method comprising the steps, performed for each frame, of:
- analyzing a first linear prediction window to generate a first set of filter coefficients for a frame;
analyzing a second linear prediction window to generate a second set of filter coefficients for the frame;
analyzing a first pitch analysis window to generate a first pitch estimate for the frame;
analyzing a second pitch analysis window to generate a second pitch estimate for the frame;
determining whether the frame is one of a first mode, a second mode and a third mode, depending on measures of energy content of the frame and spectral content of the frame;
encoding the frame, depending on the second set of filter coefficients and the first and the second pitch estimates, independently of the first set of filter coefficients, when the frame is determined to be the third mode;
encoding the frame, depending on the first and the second sets of filter coefficients, independently of the first and the second pitch estimates, when the frame is determined to be the second mode; and
encoding the frame, depending on the second set of filter coefficients, independently of the first set of filter coefficients and the first and the second pitch estimates, when the frame is determined to be the first mode.
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Abstract
A method for encoding a signal that includes a speech component is described. First and second linear prediction windows of a frame are analyzed to generate sets of filter coefficients. First and second pitch analysis windows of the frame are analyzed to generate pitch estimates. The frame is classified in one of at least two modes, e.g. voiced, unvoiced and noise modes, based, for example, on pitch stationarity, short-term level gradient or zero crossing rate. Then the frame is encoded using the filter coefficients and pitch estimates in a particular manner depending upon the mode determination for the frame, preferably employing CELP based encoding algorithms.
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Citations
24 Claims
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1. A method of encoding a signal having a speech component, the signal being organized as a plurality of frames, the method comprising the steps, performed for each frame, of:
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analyzing a first linear prediction window to generate a first set of filter coefficients for a frame; analyzing a second linear prediction window to generate a second set of filter coefficients for the frame; analyzing a first pitch analysis window to generate a first pitch estimate for the frame; analyzing a second pitch analysis window to generate a second pitch estimate for the frame; determining whether the frame is one of a first mode, a second mode and a third mode, depending on measures of energy content of the frame and spectral content of the frame; encoding the frame, depending on the second set of filter coefficients and the first and the second pitch estimates, independently of the first set of filter coefficients, when the frame is determined to be the third mode; encoding the frame, depending on the first and the second sets of filter coefficients, independently of the first and the second pitch estimates, when the frame is determined to be the second mode; and encoding the frame, depending on the second set of filter coefficients, independently of the first set of filter coefficients and the first and the second pitch estimates, when the frame is determined to be the first mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An encoder for encoding a signal having a speech component, the signal being organized as a plurality of frames, comprising:
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a filter coefficient generator for analyzing a first linear prediction window to generate a first set of filter coefficients for a frame and for analyzing a second linear prediction window to generate a second set of filter coefficients for the frame; a pitch estimator for analyzing a first pitch analysis window to generate a first pitch estimate for the frame and analyzing a second pitch analysis window to generate a second pitch estimate for the frame; a mode determinator for determining whether the frame is one of a first mode, a second mode and a third mode, depending on measures of energy content of the frame and spectral content of the frame; and a frame encoder for encoding the frame depending on the determined mode of the frame, wherein a frame determined to be of a third mode is encoded depending on the second set of filter coefficients and the first and the second pitch estimates, independently of the first set of filter coefficients, a frame determined to be of a second mode is encoded depending on the first and the second sets of filter coefficients, independently of the first and the second pitch estimates, and a frame determined to be of a first mode is encoded depending on the second set of filter coefficients, independently of the first set of filter coefficients and the first and the second pitch estimates. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification