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US 7,353,169 B1Granted
Transient detection and modification in audio signals
AssigneeCreative Technology Ltd
InventorsMichael Goodwin, Carlos Avendano, Martin Wolters, Ramkumar Sridharan
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Abstract
A system and method are disclosed for transient detection and modification in audio signals. Digital signal processing techniques are used to detect transients and modify an audio signal to enhance or suppress such transients, as desired. A transient audio event is detected in a first portion of the audio signal. A graded response to the detected transient audio event is determined. The first portion of the audio signal is modified in accordance with the graded response. The extent of enhancement or suppression (as applicable) may be determined at least in part by a measure of the significance or magnitude of the transient.
Claims57
A method for modifying a transient audio event in an audio signal, comprising:
- detecting a transient audio event in a first portion of the audio signal;
- determining a graded response to the detected transient audio event;
- and
- modifying said first portion of the audio signal in accordance with the graded response;
- wherein detecting a transient audio event comprises calculating a normalized spectral flux value associated with said first portion of the audio signal, including:
- calculating a spectral flux value for a frame of the audio signal that is currently being analyzed;
- and
- dividing said spectral flux value for a frame of the audio signal that is currently being analyzed by a normalization factor.
5 more elements
A method for modifying a transient audio event in an audio signal, comprising:
- detecting a transient audio event in a first portion of the audio signal;
- determining a graded response to the detected transient audio event;
- and
- modifying said first portion of the audio signal in accordance with the graded response, wherein:
- detecting a transient audio event comprises calculating a spectral flux value associated with said first portion of the audio signal;
- calculating a spectral flux value comprises processing said audio signal using a subband filter bank;
- processing said audio signal using a subband filter bank comprises:
- determining the short-time Fourier transform (STFT) for a first frame of the audio signal;
- determining the short-time Fourier transform (STFT) for a second frame of the audio signal, wherein the second frame of the audio signal is subsequent in the time domain to the first frame of the audio signal;
- and
- comparing the STFT result for the second frame with the STFT result for the first frame;
- and
- comparing the STFT result for the second frame with the STFT result for the first frame comprises summing the square root of the absolute value of the differences in spectral magnitude between the STFT result for the second frame and the STFT result for the first frame.
10 more elements
A method for modifying a transient audio event in an audio signal, comprising:
- detecting a transient audio event in a first portion of the audio signal;
- determining a graded response to the detected transient audio event;
- and
- modifying said first portion of the audio signal in accordance with the graded response, wherein:
- modifying said first portion of the audio signal in accordance with the graded response comprises nonlinear modification of said first portion of said audio signal;
- said nonlinear modification comprises:
- determining the spectral magnitude of said first portion of the audio signal;
- and
- applying a nonlinear modification to said spectral magnitude of said first portion of the audio signal to yield a modified spectral magnitude value;
- and
- applying a nonlinear modification to said spectral magnitude of said first portion of the audio signal comprises raising said spectral magnitude to an exponent equal to a modification factor.
8 more elements
A method for modifying a transient audio event in an audio signal, comprising:
- detecting a transient audio event in a first portion of the audio signal;
- determining a graded response to the detected transient audio event;
- and
- modifying said first portion of the audio signal in accordance with the graded response, wherein:
- modifying said first portion of the audio signal in accordance with the graded response comprises nonlinear modification of said first portion of said audio signal;
- said nonlinear modification comprises:
- determining the spectral magnitude of said first portion of the audio signal;
- and
- applying a nonlinear modification to said spectral magnitude of said first portion of the audio signal to yield a modified spectral magnitude value;
- and
- applying a nonlinear modification to said spectral magnitude of said first portion of the audio signal comprises adding one to said spectral magnitude of said first portion of the audio signal to obtain a first intermediate result, raising said first intermediate result to an exponent equal to a modification factor to obtain a second intermediate result, and then subtracting one from said second intermediate result to obtain said modified spectral magnitude value.
8 more elements
A method for modifying a transient audio event in an audio signal, comprising:
- detecting a transient audio event in a first portion of the audio signal;
- determining a graded response to the detected transient audio event;
- and
- modifying said first portion of the audio signal in accordance with the graded response, wherein:
- modifying said first portion of the audio signal in accordance with the graded response comprises nonlinear modification of said first portion of said audio signal;
- said nonlinear modification comprises:
- determining the spectral magnitude of said first portion of the audio signal;
- and
- applying a nonlinear modification to said spectral magnitude of said first portion of the audio signal to yield a modified spectral magnitude value;
- and
- modifying said first portion of the audio signal in accordance with the graded response further comprises:
- dividing said modified spectral magnitude value by the corresponding original, unmodified spectral magnitude value to obtain a modification ratio;
- and
- multiplying a frequency-domain representation of said first portion of said audio signal by said modification ratio to obtain a modified frequency-domain representation of said first portion of said audio signal;
- whereby the spectral magnitude of said modified frequency-domain representation of said first portion of said audio signal matches said modified spectral magnitude value.
12 more elements
A method for modifying a transient audio event in an audio signal, comprising:
- detecting a transient audio event in a first portion of the audio signal;
- and
- applying a nonlinear modification to said first portion of the audio signal;
- wherein applying a nonlinear modification comprises:
- determining the spectral magnitude of said first portion of the audio signal;
- applying a nonlinear modification to said spectral magnitude of said first portion of the audio signal to yield a modified spectral magnitude value;
- dividing said modified spectral magnitude value by the corresponding original, unmodified spectral magnitude value to obtain a modification ratio;
- and
- multiplying a frequency-domain representation of said first portion of said audio signal by said modification ratio to obtain a modified frequency-domain representation of said first portion of said audio signal;
- whereby the spectral magnitude of said modified frequency-domain representation of said first portion of said audio signal matches said modified spectral magnitude value.
7 more elements
A system for modifying transient audio events in an audio signal, comprising:
- a transient detector configured to detect a transient audio event in a first portion of the audio signal;
- a graded response determination module configured to determine a graded response to the detected transient audio event;
- and
- a modification module configured to modify said first portion of the audio signal in accordance with the graded response;
- wherein the transient detector is configured to detect the transient at least in part by calculating a normalized spectral flux associated with said first portion of the audio signal, including:
- calculating a spectral flux value for a frame of the audio signal that is currently being analyzed;
- and
- dividing said spectral flux value for a frame of the audio signal that is currently being analyzed by a normalization factor.
5 more elements
A system for modifying a transient audio event in an audio signal, comprising:
- a data input line configured to receive said audio signal;
- and
- a processor configured to:
- detect a transient audio event in a first portion of the audio signal;
- determine a graded response to the detected transient audio event;
- and
- modify said first portion of the audio signal in accordance with the graded response;
- wherein the processor is configured to detect the transient audio event at least in part by calculating a normalized spectral flux value associated with said first portion of the audio signal, including:
- calculating a spectral flux value for a frame of the audio signal that is currently being analyzed;
- and
- dividing said spectral flux value for a frame of the audio signal that is currently being analyzed by a normalization factor.
8 more elements
A computer program product for modifying a transient audio event in an audio signal, the computer program product being embodied in a computer-readable medium and comprising computer instructions for:
- detecting a transient audio event in a first portion of the audio signal;
- determining a graded response to the detected transient audio event;
- and
- modifying said first portion of the audio signal in accordance with the graded response;
- wherein said computer instructions for detecting a transient audio event include computer instructions for calculating a normalized spectral flux value associated with said first portion of the audio signal, including:
- calculating a spectral flux value for a frame of the audio signal that is currently being analyzed;
- and
- dividing said spectral flux value for a frame of the audio signal that is currently being analyzed by a normalization factor.
5 more elements
Dependencies are inferred from the claim text.