Apple Inc.

Kevin Christopher Rogers

Alan Cannistraro

William George Stewart

Kelly B Jacklin

Roger A Powell

Doug Wyatt

A digital audio signal can be processed using continuously variable time-frequency resolution by selecting a portion of an input digital audio signal, resampling the selected portion of the input digital audio signal, generating a plurality of spectral characteristics associated with the resampled portion of the input digital audio signal, generating a portion of an output digital audio signal from the plurality of spectral characteristics, and resampling the portion of the output digital audio signal. Further, resampling the selected portion of the input digital audio signal can comprise determining a sampling ratio and resampling the selected portion of the input digital audio signal in accordance with the determined sampling ratio. Additionally, the portion of the output digital audio signal can be resampled in accordance with the inverse of the determined sampling ratio. The sampling ratio can be determined based on a time-frequency resolution requirement associated with an audio processing algorithm.

Pre-resampling to achieve continuously variable analysis time/frequency resolution

Some embodiments of the invention provide a computer system for processing an audio track. This system includes at least on DSP for processing the audio track. It also includes an application for editing the audio track. To process audio data in a first interval of the audio track, the application first asks and obtains from the DSP an impulse response parameter related to the DSP's processing of audio data. From the received impulse response parameter, the application identifies a second audio track interval that is before the first interval. To process audio data in the first interval, the application then directs the DSP to process audio data within the first and second intervals.

Method and apparatus for efficiently accounting for the temporal nature of audio processing

A transient echo can be avoided during time stretching of a digital audio signal by detecting a transient in a frame of a digital audio signal, identifying another occurrence of the transient in a subsequent frame of the digital audio signal, rotating the transient occurring in the subsequent frame to align the transient occurring in the subsequent frame with the transient detected in the frame, and aggregating the frame with the subsequent frame. Further, another occurrence of the transient can be identified in another subsequent frame of the digital audio signal and it can be determined that the transient occurring in that subsequent frame cannot be aligned with the transient detected in the frame. The copy of the transient occurring in the another subsequent frame can then be blended across that frame, such as by performing phase accumulation on one or more frequency components.

Echo avoidance in audio time stretching

A transient in a digital audio signal can be detected by generating a first set of spectral characteristics associated with a first portion of the digital audio signal and a second set of spectral characteristics associated with a second portion of the digital audio signal, wherein the first and second portions of the digital audio signal partially overlap, comparing values in the first set of spectral characteristics with corresponding values in the second set of spectral characteristics to generate a set of ratios, weighting the set of ratios, and analyzing at least a portion of the weighted set of ratios to detect a transient associated with the first portion of the digital audio signal. Further, an indicator identifying the presence of a detected transient can be output. Additionally, one or more ratios in the set of ratios can be weighted based on amplitude, frequency, or a power function.

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Albany, CA, United States of America

Kevin Christopher Rogers