Dynamic bass boost apparatus and method
First Claim
1. An audio processor comprising:
- a variable filter receiving an input signal and providing an output signal, said variable filter having a quality factor that is controlled in response to a control signal, while a cutoff frequency of the variable filter remains fixed; and
a control circuit configured to detect a signal level in the output signal representative of an input signal level in a selected band and to generate the control signal in response to the detected signal level, wherein a magnitude of the control signal is a function of an amplitude of the output signal within the selected band.
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Abstract
Audio processing methods and apparatus are provided for at least partially compensating for the Fletcher-Munson effect. An audio processor includes a variable filter receiving an input signal and providing a filtered output signal, the variable filter having a fixed cutoff frequency and a quality factor that is controllable in response to a control signal, and a control circuit configured to detect a signal level representative of input signal level in a selected band and to generate the control signal in response to the detected signal level. The control circuit may include a low-pass band select filter and a detector for detecting a signal level in the band selected by the low-pass filter and for generating the control signal.
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Citations
54 Claims
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1. An audio processor comprising:
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a variable filter receiving an input signal and providing an output signal, said variable filter having a quality factor that is controlled in response to a control signal, while a cutoff frequency of the variable filter remains fixed; and a control circuit configured to detect a signal level in the output signal representative of an input signal level in a selected band and to generate the control signal in response to the detected signal level, wherein a magnitude of the control signal is a function of an amplitude of the output signal within the selected band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An audio processor comprising:
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a variable filter receiving an input signal and providing a filtered output signal, said variable filter having a quality factor that is controlled in response to a control signal, while a cutoff frequency of the variable filter remains fixed; a low-pass filter for selecting a band of the output signal; and a detector for detecting a signal level in the band selected by the low-pass filter and for generating the control signal in response to the detected signal level, wherein said variable filter further comprises a variable gain element responsive to the control signal and configured to amplify a bass frequency band of the input signal, and wherein a magnitude of the control signal is a function of an amplitude of the output signal within the selected band. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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38. An audio processing method comprising the steps of:
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filtering an input signal in a variable filter and providing a filtered output signal, where the variable filter has a quality factor that is controlled in response to a control signal, while a cutoff frequency of the variable filter remains fixed; detecting a signal level representative of input signal level in a selected band to provide a detected signal level; and amplifying a bass frequency band of the input signal in response to the detected signal level. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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51. An audio processor comprising:
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a state variable digital high-pass filter receiving an input data stream and providing a filtered output data stream, said digital filter having a quality factor that is controlled in response to a control variable, while a cutoff frequency of the variable filter remains fixed; a digital band select filter for selecting a band of the output data stream; and a detector algorithm for detecting a signal level in the band selected by the digital band select filter and for generating the control variable in response to the detected signal level, wherein the state variable digital high-pass filter includes a lookup table for establishin a desired relationship between the quality factor of the state variable digital high-pass filter and the detected signal level.
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52. An audio processor comprising:
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a variable filter receiving an input signal and providing an output signal, said variable filter having a fixed cutoff frequency and a quality factor that is controllable in response to a control signal, wherein the variable filter comprises a fixed band-pass filter in series with a variable gain element responsive to the control signal to provide a controlled band-pass signal, and a summer for combining the controlled band-pass signal and the input signal to provide the output signal; and a control circuit configured to detect a signal level representative of input signal level in a selected band and to generate the control signal in response to the detected signal level.
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53. An audio processor comprising:
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a variable filter receiving an input signal and providing an output signal, said variable filter having a fixed cutoff frequency and a quality factor that is controllable in response to a control signal, wherein the variable filter comprises a digital filter receiving an input data stream and providing a filtered output data stream, wherein the control signal comprises a control variable, and wherein the digital filter includes a lookup table for establishing a desired relationship between the quality factor of the digital filter and the detected signal level; and a control circuit configured to detect a signal level representative of input signal level in a selected band and to generate the control signal in response to the detected signal level.
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54. An audio processing method, comprising the steps of:
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filtering an input signal in a variable filter and providing a filtered output signal, wherein filtering the input signal comprises filtering an input data stream with a digital high-pass state variable filter and providing a filtered output data stream; detecting a signal level representative of input signal level in a selected band to provide a detected signal level; and controlling a quality factor of the variable filter in response to the detected signal level, wherein controlling the quality factor of the variable filter comprises accessing control values in a lookup table in response to the detected signal level.
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Specification