US 2025/0029621 A1Published application

Harmonic transposition in an audio coding method and system

AssigneeDolby International AB

InventorsPer EKSTRAND, Lars VILLEMOES

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Abstract

The present invention relates to transposing signals in time and/or frequency and in particular to coding of audio signals. More particular, the present invention relates to high frequency reconstruction (HFR) methods including a frequency domain harmonic transposer. A method and system for generating a transposed output signal from an input signal using a transposition factor T is described. The system comprises an analysis window of length La, extracting a frame of the input signal, and an analysis transformation unit of order M transforming the samples into M complex coefficients. M is a function of the transposition factor T. The system further comprises a nonlinear processing unit altering the phase of the complex coefficients by using the transposition factor T, a synthesis transformation unit of order M transforming the altered coefficients into M altered samples, and a synthesis window of length Ls, generating a frame of the output signal.

Claims12

Dependent claims

An audio signal processing device for transposing an input audio signal by a transposition factor T to generate an output audio signal, the audio signal processing device comprising one or more components that:

extract a frame of L time-domain samples of the input audio signal using an analysis window of length L having the function
v
⁡
(
n
)
=
sin
⁡
(
π
L
⁢
(
n
+
0
.
5
)
)
,
0≤n<L;
convert the L time-domain samples into M complex frequency-domain coefficients;
alter a phase of the complex frequency-domain coefficients by converting one or more of the complex frequency-domain coefficients to a polar representation, and multiplying the phase of the polar representation by the transposition factor T;
convert the altered frequency-domain coefficients into M altered time-domain samples;
and
create a frame of L time-domain output samples of the output audio signal from the M altered time-domain samples using a synthesis window;
wherein M=F*L, with F being a frequency domain oversampling factor determined in response to frequency domain oversampling information received in an encoded bitstream;
and
wherein the frame of L time-domain output samples of the output audio signal comprises a plurality of high frequency components not present in the frame of L time-domain samples of the input audio signal, at least one of the high frequency components is generated using the transposition factor T, and at least one other of the high frequency components is generated using a second transposition factor T2, wherein T is not equal to T2.

28 more elements

A method, performed by an audio signal processing device, for transposing an input audio signal by a transposition factor T to generate an output audio signal, the method comprising:

extracting a frame of L time-domain samples of the input audio signal using an analysis window of length L having the function
v
⁡
(
n
)
=
sin
⁡
(
π
L
⁢
(
n
+
0
.
5
)
)
,
0≤n<L;
transforming the L time-domain samples into M complex frequency-domain coefficients;
altering a phase of the complex frequency-domain coefficients by converting one or more of the complex frequency-domain coefficients to a polar representation, and multiplying the phase of the polar representation by the transposition factor T;
transforming the altered frequency-domain coefficients into M altered time-domain samples;
and
generating a frame of L time-domain output samples of the output audio signal from the M altered time-domain samples using a synthesis window;
wherein M=F*L, with F being a frequency domain oversampling factor determined in response to frequency domain oversampling information received in an encoded bitstream;
and
wherein the frame of L time-domain output samples of the output audio signal comprises a plurality of high frequency components not present in the frame of L time-domain samples of the input audio signal, at least one of the high frequency components is generated using the transposition factor T, and at least one other of the high frequency components is generated using a second transposition factor T2, wherein T is not equal to T2.

28 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/905,649Filed 3 Oct 2024
Priority: WO PCT/EP2010/05322212 Mar 2010
Published: 23 Jan 2025
Term ends: Not estimatedThe source records don’t support an estimate.

Classification6 codes

G10L 19/022
Using spectral analysis, e.g. transform vocoders or subband vocoders: blocking, i.e. grouping of samples in time; Choice of analysis windows;…
G10L 19/0212
Using spectral analysis, e.g. transform vocoders or subband vocoders: using orthogonal transformation
G10L 19/24
Vocoders using multiple modes: variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical…
G10L 21/038
Speech enhancement, e.g. noise reduction or echo cancellation: using band spreading techniques

Family

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Application18/905,649Continuation
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