System and method for masking quantization noise of audio signals
First Claim
1. A method for masking quantization noise by spectrally weighting transform coefficients of an input signal having a given bandwidth and produced by a transform processor, comprising:
- calculating a masking spectral threshold in a quasi-logarithmic scale that approximates critical bands of a hearing model by applying triangular decays to spectral peaks;
computing plural spread masking thresholds in each critical band as a maximum of contributions from the triangular decays; and
adjusting the spread masking thresholds to produce an absolute threshold.
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Abstract
The coder/decoder (codec) system of the present invention includes a coder and a decoder. The coder includes a multi-resolution transform processor, such as a modulated lapped transform (MLT) transform processor, a weighting processor, a uniform quantizer, a masking threshold spectrum processor, an entropy encoder, and a communication device, such as a multiplexor (MUX) for multiplexing (combining) signals received from the above components for transmission over a single medium. The decoder comprises inverse components of the encoder, such as an inverse multi-resolution transform processor, an inverse weighting processor, an inverse uniform quantizer, an inverse masking threshold spectrum processor, an inverse entropy encoder, and an inverse MUX. With these components, the present invention is capable of performing resolution switching, spectral weighting, digital encoding, and parametric modeling.
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Citations
20 Claims
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1. A method for masking quantization noise by spectrally weighting transform coefficients of an input signal having a given bandwidth and produced by a transform processor, comprising:
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calculating a masking spectral threshold in a quasi-logarithmic scale that approximates critical bands of a hearing model by applying triangular decays to spectral peaks; computing plural spread masking thresholds in each critical band as a maximum of contributions from the triangular decays; and adjusting the spread masking thresholds to produce an absolute threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A noise masking device stored on computer readable memory of a computer system for masking quantization noise by spectrally weighting transform coefficients of an input audio signal having a given bandwidth and produced by a transform processor, comprising:
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a threshold processor for calculating a masking spectral threshold in a quasi-logarithmic scale that approximates critical bands of a hearing model by applying triangular decays to spectral peaks; a spread processor for computing plural spread masking thresholds in each critical band as a maximum of contributions from the triangle decays; and an adjustment module for adjusting the spread masking thresholds to produce an absolute threshold for efficiently masking unwanted noise of the audio signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification