Method for time scaling of a sequence of input signal values

• US 20100004937A1
• Filed: 06/22/2009
• Published: 01/07/2010
• 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
• Granted Patent: US 8,676,584 B2
• Time in Patent Office: Days
• US Class Current: 704/503
• 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. Method for time scaling a sequence of input signal values using a modified waveform similarity overlap add approach, wherein

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.

2. Method according to claim 1, wherein

said first pair comprises a first matching sub-sequences and said second pair comprises different second matching sub-sequences.

3. Method according to claim 1, wherein

said first pair and said second pair comprise a same matching sub-sequence.

4. Method according to claim 1, wherein

modification of said waveform similarity overlap add approach comprises copying sub-sequences until an accumulated temporal deviation 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 sub-sequences and an aspired time scaling factor.

5. Method according to claim 1, wherein

the similarity measure of each sub-sequence pair comprises a weighting which takes into account the temporal distance between the sub-sequences of the pair.

6. Method according to claim 5, wherein

said weighting is biased towards larger temporal distances.

7. Method according to claim 1, wherein

the input window is determined such that it comprises at least one pause signal segment.

8. Method according to claim 1, wherein

the input window is determined such that it does not comprise any transient signal segment.

9. Device comprising means for time scaling a sequence of input signal values using a modified waveform similarity overlap add approach, said means being adapted for determining a maximized similarity 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 first sub-sequence to-be-matched and at least a second pair comprises a different second sub-sequence to-be-matched.

10. Device according to claim 9, wherein

said first pair comprises a first matching sub-sequences and said second pair comprises different second matching sub-sequences.

11. Method according to claim 9, wherein

said first pair and said second pair comprise a same matching sub-sequence.

12. Device according to claim 9, wherein

said means are further adapted for copying sub-sequences until an accumulated temporal deviation which results from said copying is equal to or larger than a minimum hop distance, said accumulated temporal deviation depending on an accumulated temporal duration of the copied sub-sequences and an aspired time scaling factor.

13. Device according to claim 9, wherein

the similarity measure of each sub-sequence pair comprises a weighting which takes into account the temporal distance between the sub-sequences of the pair.

14. Device according to claim 13, wherein

said weighting is biased towards larger temporal distances.

15. Device according to claim 9, wherein

said means are further adapted for determining the input window such that it comprises at least one pause signal segment and/or such that it does not comprise any transient signal segment.