Noise shaping circuit and noise shaping method
AssigneeSony Corporation
InventorTohru Sugihara
Life of this patent
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Abstract
A noise shaping circuit and a noise shaping method, in which a quantization error generated in a requantizer is taken out at a subtractive node and fed back to an input of the requantizer via a noise filter. A dc detector detects if the input signal from an input terminal is of a dc value including zero. If the input signal is detected to be a dc signal, the feedback quantity is reset to zero to prevent the oscillation by the limit cycle and to prevent the hunting phenomenon from occurring.
Claims17
A noise shaping circuit for use in transmitting a digital input signal in which quantization noise generated by a quantizer is fed back as a feedback signal via a noise filter to an input side of said quantizer comprising:
- means for detecting whether the digital input signal has a dc value including zero and,
- means for setting the feedback signal to zero when the dc value is detected by the means for detecting.
A noise shaping circuit for use in transmitting a digital signal in which quantization noise generated by a quantizer is fed back as a feedback signal via a noise filter to an input side of said quantizer comprising:
- detection means for detecting that lower order bits of a pre-set number of consecutive samples of an input digital signal remain constant, and
- means for setting the feedback signal to zero when the lower order bits are detected to be constant.
A method of transmitting digital signals employing noise shaping in which quantization noise generated by a quantizer is fed back as a feedback signal via a noise filter to an input side of said quantizer comprising the steps of:
- detecting whether input digital signal are of a dc value including zero, and
- reducing a level of the feedback signal fed to the quantizer to zero if the dc value is detected in the detecting step.
A method of transmitting digital signals, comprising the steps of:
- receiving an digital input audio signal;
- subtracting an error feedback signal from said input audio signal to produce a main signal;
- quantizing said main signal to produce a quantized main signal;
- generating a difference signal by subtracting said main signal from said quantized main signal;
- filtering said difference signal to produce said error feedback signal;
- detecting whether said digital input audio signal has a constant value over a predetermined number of samples;
- reducing said error feedback to zero when said constant value is detected;
- and
- transmitting said quantized main signal.
Apparatus for transmitting digital signals comprising:
- means for receiving an input digital audio signal;
- means for subtracting a noise feedback signal from said input signal to produce a main signal;
- means for quantizing said main signal to produce a quantized output signal;
- means for generating a noise signal by subtracting said main signal from said quantized output signal;
- a digital filter including a plurality of coefficients for receiving said noise signal and producing said noise feedback signal;
- and
- means for detecting whether said input digital audio signal has a constant value over a predetermined number of samples thereof and producing a control signal indicating a result of said detecting, said control signal being fed to said digital filter for setting said plurality of coefficients to zero upon detecting said constant value.
Dependencies are inferred from the claim text.