Dynamic audio enhancement using an all-pass filter
AssigneeBambu Tech, Inc.
InventorsEarnest Lloyd Trammel, John Raymond Gould
Life of this patent
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Abstract
An input audio signal is all-pass filtered and scaled, before being combined with an original version of the input audio signal, to produce an output signal. Envelope of the input signal is detected and the all-pass filter is altered dynamically or in real time, as a function of the detected envelope. Other embodiments are also described and claimed.
Claims21
A digital signal processing method for enhancing realism of an input audio signal, comprising:
- a. filtering an input audio signal using an all-pass filter, to produce an all-pass filtered version;
- b. scaling the all-pass filtered version to produce a scaled, all-pass filtered version;
- c. combining the scaled, all-pass filtered version with the input audio signal, to form an output audio signal;
- d. detecting envelope of the input audio signal, while performing the filtering in a., the scaling in b., and the combining in c.;
- and
- e. altering the all-pass filter as a function of the detected envelope of the input audio signal.
The method of any one of the previous claims wherein detecting envelope of the input audio signal comprises
- computing a moving average of an amplitude of the input audio signal, wherein the detected envelope is updated as the moving average, at a rate of between every sample to every ten samples of the input audio signal.
The method of any one of the previous claims further comprising low pass filtering the input audio signal to produce a low pass filtered version, wherein filtering the input audio signal using the all-pass filter comprises filtering the low pass filtered version.
The method of any one of the previous claims further comprising encoding the output audio signal using a lossy compression algorithm.
A digital audio signal processor configured to process an input audio signal for enhancing its realism, comprising:
- a. an all-pass filter having an input to receive an input audio signal, and a control input through which phase response of the all-pass filter is varied;
- b. a gain element having an input coupled to an output of the all-pass filter;
- c. a summing unit having a first input coupled to an output of the gain element, a second input to receive the input audio signal which bypasses the all-pass filter and the gain element;
- and
- d. a modulation generator having an input to receive the input audio signal which bypasses the all-pass filter and the gain element, wherein the modulation generator has an output coupled to the control input of the all-pass filter.
An article of manufacture comprising:
- a non-transitory machine-readable medium having stored therein instructions that when executed by a processor
- a. filter an input audio signal using an all-pass filter, to produce an all-pass filtered version;
- b. scale the all-pass filtered version to produce a scaled, all-pass filtered version;
- c. combine the scaled, all-pass filtered version with the input audio signal, to form an output audio signal;
- d. detect envelope of the input audio signal, while performing the filtering in a., the scaling in b., and the combining in c.;
- and
- e. alter the all-pass filter as a function of the detected envelope of the input audio signal, while performing the filtering in a., the scaling in b., and the combining in c.
Dependencies are inferred from the claim text.