Removing periodicity from a lengthened audio signal
AssigneeU.S. Philips Corporation
InventorErcan F. Gigi
Life of this patent
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Abstract
An audio equivalent input signal is divided into a sequence of overlapping or adjacent signal segments. A lengthened signal is synthesized by systematically maintaining or repeating respective signal segments of the sequence of segments. Repeating non-periodic segments, such as a voiceless part of a speech signal or noise in music, results in audible artefacts. The introduced periodicity is broken by dividing a signal section originating from one non-periodic source signal segment into a second sequence of signal segments with at least one of the signal segments having a duration not equal to a duration of the source signal segment and not equal to a multiple of the duration of the source signal segment. Signal segments of the second sequence are shuffled.
Claims9
A method for lengthening an audio equivalent input signal, the method comprising the steps of:
- positioning a first chain of mutually overlapping or adjacent time windows with respect to the signal, each time window being associated with a respective window function;
- forming a first sequence of signal segments by weighting the signal according to the associated window function of a respective window of the first chain of windows;
- and
- synthesising a lengthened audio signal by systematically maintaining or repeating respective signal segments of the first sequence of signal segments;
- identifying a signal section in the lengthened audio signal which is synthesised from one of the signal segments, referred to as a source signal segment, by maintaining and at least once repeating the source signal segment;
- the source signal segment substantially having no periodic component;
- and
- breaking periodicity in the signal section caused by repeating the source signal segment by
- positioning a second chain of mutually overlapping or adjacent time windows with respect to the signal section;
- at least some of the time windows of the second chain having a duration not equal to a duration of the source signal segment and not equal to a multiple of the duration of the source signal segment;
- forming a second sequence of signal segments by weighting the signal section with the associated window function of a respective window of the second chain of windows;
- and
- generating an audio output signal from the lengthened audio signal by shuffling signal segments of the second sequence of signal segments.
An apparatus for lengthening an audio equivalent input signal, the apparatus comprising:
- positioning means for positioning a first chain of mutually overlapping or adjacent time windows with respect to the signal, each time window being associated with a respective window function;
- segmenting means for forming a first sequence of signal segments by weighting the signal according to the associated window function of a respective window of the first chain of windows;
- and
- synthesising means for synthesising a lengthened audio signal by systematically maintaining or repeating respective signal segments of the first sequence of signal segments,
- characterised in that the apparatus comprises:
- identification means for identifying a signal section in the lengthened audio signal which is synthesised from one of the signal segments, referred to as a source signal segment, by maintaining and at least once repeating the source signal segment, the source signal segment substantially having no periodic component;
- and
- means for breaking periodicity in the signal section caused by repeating the source signal segment by
- causing the positioning means to position a second chain of mutually overlapping or adjacent time windows with respect to the signal section;
- at least some of the time windows of the second chain having a duration not equal to a duration of the source signal segment and not equal to a multiple of the duration of the source signal segment;
- causing the segmenting means to form a second sequence of signal segments by weighting the signal section with the associated window function of a respective window of the second chain of windows;
- and
- generating an audio output signal from the lengthened audio signal by shuffling signal segments of the second sequence of signal segments.
Dependencies are inferred from the claim text.