Method for time scaling of a sequence of input signal values

• US 8,676,584 B2
• Filed: 06/22/2009
• Issued: 03/18/2014
• Est. Priority Date: 07/03/2008
• Status: Active Grant

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Schlosser, Markus
• Primary Examiner(s): YEN, ERIC L
• Application Number:
  US12/456,741
• Publication Number:
  US 20100004937A1
• Time in Patent Office: 1,730 Days
• Field of Search: 704/258, 704/260, 704/203, 704/211
• US Class Current: 704/258
• CPC Class Codes: G10L 21/04 Time compression or expansion

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.

Claims

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 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.

2. The method according to claim 1, further comprising:

determining a maximized similarity among similarity measures of multiple sample sub-sequence pairs each sample sub-sequence pair comprising a sample sub-sequence to-be-matched from an input window in said original sample sequence and a matching sample sub-sequence from said search window in said original sample sequence;

wherein said multiple sample sub-sequence pairs each comprise at least two sample sub-sequence pairs of which a first sample sub-sequence pair comprises a first sample sub-sequence to-be-matched and a second sample sub-sequence pair comprises a second sample sub-sequence to-be-matched that is different from said first sample sub-sequence to-be-matched;

and wherein said first sample sub-sequence pair comprises a first matching sample sub-sequence and said second sample sub-sequence pair comprises a second matching sample sub-sequence that is different from said first matching sample sub-sequence.

3. The method according to claim 2, further comprising:

copying sample sub-sequences from said original sample sequence until an accumulated temporal deviation for said time-scaled sample sequence which results from said copying is equal to or larger than a predetermined minimum temporal deviation, said accumulated temporal deviation depending on an accumulated temporal duration of the copied sample sub-sequences and an aspired time scaling factor.

4. The method according to claim 2,

wherein each similarity measure of the similarity measures of multiple sample sub-sequence pairs is weighted by taking into account the temporal distance between the sample sub-sequences of a respective sample sub-sequence pair.

5. The method according to claim 2, wherein said input window is determined such that it comprises at least one pause signal segment.

6. The method according to claim 2, wherein said input window is determined such that it does not comprise any transient signal segment.