Method for time scaling of a sequence of input signal values
First Claim
1. A method for time-scaling an original sample sequence by copying samples of a sub-sequence directly following a current sub-sequence of said original sample sequence to a time-scaled sample sequence which is a time-scaled version of said original sample sequence, said time-scaling and copying being based on waveform similarity overlap-add processing, said method comprising:
- performing, by a processor, operations of;
appending to a current sub-sequence of said time-scaled sample sequence a copy of a subsequence of said original sample sequence, which copied sub-sequence of said original sample sequence directly follows the current sub-sequence of said original sample sequence;
if copying of samples of successive sub-sequences of said original sample sequence to said time-scaled sample sequence would result in an exceeding of a temporal deviation threshold for said time-scaled sample sequence, instead of appending a copy of a sub-sequence which directly follows a current sub-sequence of samples of said original sample sequence to the time-scaled sample sequence, appending a copy of a temporally advanced sub-sequence of samples of said original sample sequence to the time-scaled sample sequence, which temporally advanced sub-sequence of samples of said original sample sequence has a temporal position which either temporally precedes or temporally follows the temporal position of said sub-sequence which directly follows a current sub-sequence of samples of said original sample sequencewherein the temporally advanced sub-sequence is determined to be most similar to said sub-sequence which directly follows a current sub-sequence of samples of said original sample sequence, wherein the determination is based on a measure of similarity which is weighted such that the measure of similarity is biased towards a larger temporal distance between said temporally advanced sub-sequence and the current sub-sequence which is directly followed by said sub-sequence which directly follows a current sub-sequence of samples of said original sample sequence,and wherein the temporally advanced sub-sequence lies within a search window in said original sample sequence that is located at a temporal position determined by a scaling factor associated with said time-scaled sample sequence.
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Abstract
The invention relates to a digital signal processing technique that changes the length of an audio signal and, thus, effectively its play-out speed. This is used for frame rate conversion or sound effects in music production. Time scaling may further be used for fast forward or slow-motion audio play-out.
According said method the waveform similarity overlap add approach is modified such that a maximized similarity is determined among similarity measures of sub-sequence pairs each comprising a sub-sequence to-be-matched from a input window and a matching sub-sequence from a search window wherein said sub-sequence pairs comprise at least two sub-sequence pairs of which a first pair comprises a first sub-sequence to-be-matched and a second pair comprises a different second sub-sequence to-be-matched.
The input window allows for finding sub-sequence pairs with higher similarity than with a WSOLA approach based on a single sub-sequence to-be-matched. This results in less perceivable artefacts.
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Citations
6 Claims
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1. A method for time-scaling an original sample sequence by copying samples of a sub-sequence directly following a current sub-sequence of said original sample sequence to a time-scaled sample sequence which is a time-scaled version of said original sample sequence, said time-scaling and copying being based on waveform similarity overlap-add processing, said method comprising:
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performing, by a processor, operations of; appending to a current sub-sequence of said time-scaled sample sequence a copy of a subsequence of said original sample sequence, which copied sub-sequence of said original sample sequence directly follows the current sub-sequence of said original sample sequence; if copying of samples of successive sub-sequences of said original sample sequence to said time-scaled sample sequence would result in an exceeding of a temporal deviation threshold for said time-scaled sample sequence, instead of appending a copy of a sub-sequence which directly follows a current sub-sequence of samples of said original sample sequence to the time-scaled sample sequence, appending a copy of a temporally advanced sub-sequence of samples of said original sample sequence to the time-scaled sample sequence, which temporally advanced sub-sequence of samples of said original sample sequence has a temporal position which either temporally precedes or temporally follows the temporal position of said sub-sequence which directly follows a current sub-sequence of samples of said original sample sequence wherein the temporally advanced sub-sequence is determined to be most similar to said sub-sequence which directly follows a current sub-sequence of samples of said original sample sequence, wherein the determination is based on a measure of similarity which is weighted such that the measure of similarity is biased towards a larger temporal distance between said temporally advanced sub-sequence and the current sub-sequence which is directly followed by said sub-sequence which directly follows a current sub-sequence of samples of said original sample sequence, and wherein the temporally advanced sub-sequence lies within a search window in said original sample sequence that is located at a temporal position determined by a scaling factor associated with said time-scaled sample sequence. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification