Noise and bit rate reduction arrangements
First Claim
1. A method for reducing bandwidth in a digital signal processing system comprising the steps ofpartitioning an input signal into a succession of frames,generating signals representative of the spectral energy of the input signal in each frame,removing a portion of the input signal spectrum in each frame responsive to the spectral energy signals to form a modified input signal, said removing step comprising, attenuating a portion of the input signal spectrum in each frame corresponding to a predetermined percentage of the total spectral energy in the frame, andcoding the modified input signal.
1 Assignment
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Accused Products
Abstract
Improved digital encoding of an input speech signal for transmission uses an adaptive low-pass filter and adaptive coder responsive to the total spectral energy of the input signal, thereby providing reduced coder bit rate at constant coder noise, or conversely reduced coder noise at constant bit rate.
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Citations
18 Claims
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1. A method for reducing bandwidth in a digital signal processing system comprising the steps of
partitioning an input signal into a succession of frames, generating signals representative of the spectral energy of the input signal in each frame, removing a portion of the input signal spectrum in each frame responsive to the spectral energy signals to form a modified input signal, said removing step comprising, attenuating a portion of the input signal spectrum in each frame corresponding to a predetermined percentage of the total spectral energy in the frame, and coding the modified input signal.
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8. Apparatus for reducing bandwidth in a digital signal processing system comprising
means for partitioning an input signal into a succession of frames, means for generating signals representative of the spectral energy of the input signal in each frame, means for removing in each frame a portion of the input signal spectrum responsive to the spectral energy signals to form a modified input signal, said removing means comprising means for attenuating a portion of the input signal spectrum in each frame corresponding to a predetermined percentage of the total spectral energy in the frame, and means for coding the modified input signal.
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15. Apparatus for reducing bandwidth in a digital signal processing system comprising
means for receiving an input speech signal, means for bandpass filtering the speech signal, means for converting the bandpass filtered signal into first digital signals; -
means for partitioning the first digital signals into a succession of overlapping frames, means responsive to the first digital signals for selecting frequency signals representative of a frequency in each frame above which a predetermined percentage of the spectral energy lies in the frame, means for filtering the first digital signals, means for altering the cutoff frequency of the first digital signal filtering means responsive to the selected frequency signals in each frame; means for converting the filtered first digital signals into a first analog signal, means for bandpass filtering the first analog signal, means for coding the filtered first analog signal, and means for multiplexing the coded signals and the selected frequency signals in each frame. - View Dependent Claims (16)
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17. A method for reducing bandwidth in a digital signal processing system comprising the steps of
receiving an input speech signal, bandpass filtering the speech signal, converting the bandpass filtered signal into first digital signals; -
partitioning the first digital signals into a succession of overlapping frames, selecting frequency signals responsive to the first digital signals representative of a frequency in each frame above which a predetermined percentage of the spectral energy lies in the frame, filtering the first digital signals, altering the cutoff frequency of the first digital signals means responsive to the selected frequency signals in each frame; converting the filtered first digital signals into a first analog signal, bandpass filtering the first analog signal, coding the filtered first analog signal, multiplexing the coded signals and the selected frequency signals in each frame. - View Dependent Claims (18)
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Specification