Abstract: Methods, digital systems, and computer readable media are provided for detection of music in an audio signal. Music is detected by partitioning the audio signal into overlapping frames, determining a fundamental frequency of a frame in the overlapping frames, including the fundamental frequency of the frame in a histogram of fundamental frequency values of frames occurring in the audio signal prior to the frame, and indicating that music is present in the audio signal when a number of occurrences of a fundamental frequency value in the histogram exceeds a threshold.

Abstract: Rebalancing of an audio signal refers to achieving a balance of perceived loudness, typically of right and left channels, given an unbalanced input. A flexible method to automatically rebalance an audio input signal is robust against noise in extreme cases through the individual channels combined in various ways as a function of the loudness ratio between input channels.

Abstract: Methods, digital systems, and computer readable media are provided for estimating change of amplitude and frequency in a digital audio signal by transforming a frame of the digital audio signal to the frequency domain, locating a frequency peak in the transformed frame, determining an interpolated peak of the located frequency peak, computing inner products of a portion of the transformed frame about the interpolated peak with a plurality of test signals, and estimating change of amplitude and change of frequency for the frequency peak from results of the inner products.

Abstract: Methods, digital systems, and computer readable media are provided for determining a predominant fundamental frequency of a frame of an audio signal by finding a maximum absolute signal value in history data for the frame, determining a number of bits for downshifting based on the maximum absolute signal value, computing autocorrelations for the frame using signal values downshifted by the number of bits, and determining the predominant fundamental frequency using the computed autocorrelations.

Abstract: A time-domain time-scale modification method based on the synchronous overlap-and-add method consists of a generalization of the envelope-matching time-scale modification method. The cross-correlation function employs n most significant bits rather than merely the sign bit of the prior envelope matching method. This provides higher accuracy for n>1. A fixed-size cross-correlation buffer is employed to eliminate the need for normalization inside the search loop. This invention makes full use of fast/parallel shift and multiply-and-accumulate (MAC) instructions of current digital signal processors to become at the same time faster and more precise than envelope-matching time-domain time-scale modification.

Abstract: This invention involves time-scale modification of audio signals. In this invention the input audio signal is separated into two frequency bands using a complementary IIR filter bank. Time-scale modification is applied separately to the individual frequency bands. The thus modified signals are recombined for output.

Abstract: This invention involves time-scale modification of audio signals. In this invention the input audio signal is separated into a plurality of frequency bands selected according to a Bark scale where each frequency band has an extent dependent upon human frequency perception via a filter bank. Time-scale modification is applied separately to the individual frequency bands. The thus modified signals are recombined for output.

Abstract: This invention involves time-scale modification of audio signals. The invention describes overlap and add time scale modification with variable input and output buffer sizes. Seamless speed change is achieved by keeping track of previously processed data to avoid discontinuities during playback speed transitions.

Abstract: A time scale modification method employs separate bands obtained through an analysis polyphase filter bank with separate time-scale modification processing for the bands. The outputs are combined using a synthesis filter bank. Some constraints are imposed on the time-scale modification processing, such a limitation of the range of overlap adjustment values for bands other than the greatest energy band, to eliminate noise due to aliasing and inter-channel phase mismatch. This invention produces output quality considerably higher than conventional time-domain time-scale modification methods for general music signals with computational requirements comparable to those of conventional time-domain time-scale modification methods.

Abstract: Audio cross-talk cancellation by inverse HRTF matrix only for low frequencies; high frequencies rely upon the natural barrier of a listener's head. The low frequency cutoff is determined by a peak in the inverse matrix of the head-related transfer functions.

Abstract: A time scale modification method employs separate bands obtained through an analysis polyphase filter bank with separate time-scale modification processing for the bands. The outputs are combined using a synthesis filter bank. Some constraints are imposed on the time-scale modification processing, such a limitation of the range of overlap adjustment values for bands other than the greatest energy band, to eliminate noise due to aliasing and inter-channel phase mismatch. This invention produces output quality considerably higher than conventional time-domain time-scale modification methods for general music signals with computational requirements comparable to those of conventional time-domain time-scale modification methods.

Abstract: An efficient time scale modification (TSM) scheme for stereo signals is proposed where the overlap point is calculated just once per stereo frame based on a downmixed signal. The proposed scheme results in significantly lower computational cost compared with conventional methods: about 1.2 to 1.3 times the amount of computation required by monoaural signals, against 2.0 times the amount of computation required by channel-independent methods. Listening tests indicate that the quality achieved is higher than conventional channel-independent approaches due to the preservation of the spatial localization of the sound.

Abstract: This invention involves time-scale modification of audio signals. In this invention the input audio signal is separated into a plurality of frequency bands via a filter bank. Time-scale modification is applied separately to the individual frequency bands. The thus modified signals are recombined for output.

Abstract: This invention is a method for binaural localization using a cascade of resonators and anti-resonators to implement an HRTF (head-related transfer function). The spectrum of the cascade reproduces the magnitude spectrum of a desired HRTF. The proposed method provides a considerably more computationally efficient implementation of HRTF filters with no detectable deterioration of output quality while saving memory when storing a large quantity of HRTFs due to the parameterization of its resonators and anti-resonators. Finally, the method offers additional flexibility since the resonators and anti-resonators can be manipulated individually during the design process, making it possible to interpolate smoothly between HRTFs, reduce spectral coloring or achieve higher accuracy at perceptually relevant frequency regions. These HRTF are useful in stereo enhancement and multi-channel virtual surround simulation.

Abstract: A time-domain time-scale modification method based on the synchronous overlap-and-add method consists of a generalization of the envelope-matching time-scale modification method. The cross-correlation function employs a fixed-size cross-correlation buffer to eliminate the need for normalization inside the search loop. This fixed-size cross-correlation buffer is the center of the overlap region corresponding to the case where the fine overlap adjustment value is set to zero. The computational cost of this invention is lower than any other method with a comparable quality.

Abstract: This invention improves the perceived quality of frequency-domain time scale modification by selection of spectral bands used in phase locking based upon a Bark scale according to the variation in human hearing frequency response. A spectral peak is identified for each band. At these peaks the phases are rotated using the phase vocoder algorithm. For a few spectral lines near these peaks, the phase differences are copied from the non-rotated spectrum. The number selected is preferably 4. Remaining spectral lines within each spectral band located farther from the peak are phase rotated using the phase vocoder algorithm. The boundaries of the spectral bands may be adjusted based upon the digital audio data to maintain important frequency groups within the same spectral band.

Abstract: A time-domain time-scale modification method based on the synchronous overlap-and-add method consists of a generalization of the envelope-matching time-scale modification method. The cross-correlation function employs n most significant bits rather than merely the sign bit of the prior envelope matching method. This provides higher accuracy for n>1. A fixed-size cross-correlation buffer is employed to eliminate the need for normalization inside the search loop. This invention makes full use of fast/parallel shift and multiply-and-accumulate (MAC) instructions of current digital signal processors to become at the same time faster and more precise than envelope-matching time-domain time-scale modification.