Method and apparatus for performing speech frame encoding mode selection in a variable rate encoding system
First Claim
1. A method of encoding a speech frame, comprising the steps of:
- selecting a first encoding mode if a normalized autocorrelation measurement parameter is exceeded by a first threshold value and if a zero crossings count parameter exceeds a second threshold value;
selecting a second encoding mode if the first encoding mode is not selected and if an energy differential measurement parameter is exceeded by a third threshold value;
selecting a third encoding mode if the first and second encoding modes are not selected and if an encoding quality parameter exceeds a fourth threshold value and if a prediction gain differential measurement parameter is exceeded by a fifth threshold value and if the normalized autocorrelation measurement parameter exceeds a sixth threshold value;
selecting a fourth encoding mode if the first, second, and third encoding modes are not selected; and
encoding the speech frame in accordance with the selected encoding mode.
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Abstract
It is an objective of the present invention to provide an optimized method of selection of the encoding mode that provides rate efficient coding of the input speech. It is a second objective of the present invention to identify and provide a means for generating a set of parameters ideally suited for this operational mode selection. Third, it is an objective of the present invention to provide identification of two separate conditions that allow low rate coding with minimal sacrifice to quality. The two conditions are the coding of unvoiced speech and the coding of temporally masked speech. It is a fourth objective of the present invention to provide a method for dynamically adjusting the average output data rate of the speech coder with minimal impact on speech quality.
48 Citations
33 Claims
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1. A method of encoding a speech frame, comprising the steps of:
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selecting a first encoding mode if a normalized autocorrelation measurement parameter is exceeded by a first threshold value and if a zero crossings count parameter exceeds a second threshold value;
selecting a second encoding mode if the first encoding mode is not selected and if an energy differential measurement parameter is exceeded by a third threshold value;
selecting a third encoding mode if the first and second encoding modes are not selected and if an encoding quality parameter exceeds a fourth threshold value and if a prediction gain differential measurement parameter is exceeded by a fifth threshold value and if the normalized autocorrelation measurement parameter exceeds a sixth threshold value;
selecting a fourth encoding mode if the first, second, and third encoding modes are not selected; and
encoding the speech frame in accordance with the selected encoding mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An encoding rate determination apparatus in a speech coder for encoding a speech frame, comprising:
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means for deriving a plurality of frame parameters; and
means for selecting a first encoding mode if a normalized autocorrelation measurement parameter is exceeded by a first threshold value and if a zero crossings count parameter exceeds a second threshold value, selecting a second encoding mode if the first encoding mode is not selected and if an energy differential measurement parameter is exceeded by a third threshold value, selecting a third encoding mode if the first and second encoding modes are not selected and if an encoding quality parameter exceeds a fourth threshold value and if a prediction gain differential measurement parameter is exceeded by a fifth threshold value and if the normalized autocorrelation measurement parameter exceeds a sixth threshold value, and selecting a fourth encoding mode if the first, second, and third encoding modes are not selected. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An encoding rate determination apparatus in a speech coder for encoding a speech frame, comprising:
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a mode measurement calculator configured to derive a plurality of frame parameters; and
a rate determination logic coupled to the mode measurement calculator and configured to select a first encoding mode if a normalized autocorrelation parameter is exceeded by a first threshold value and if a zero crossings count parameter exceeds a second threshold value, select a second encoding mode if the first encoding mode is not selected and if an energy differential parameter is exceeded by a third threshold value, select a third encoding mode if the first and second encoding modes are not selected and if an encoding quality parameter exceeds a fourth threshold value and if a prediction gain differential parameter is exceeded by a fifth threshold value and if the normalized autocorrelation parameter exceeds a sixth threshold value, and select a fourth encoding mode if the first, second, and third encoding modes are not selected. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification