Efficient combined harmonic transposition

• US 10,657,937 B2
• Filed: 04/05/2019
• Issued: 05/19/2020
• Est. Priority Date: 05/27/2009
• Status: Active Grant

• Current Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Original Assignee: Dolby International AB (Dolby Laboratories Incorporated)
• Inventors: Ekstrand, Per, Villemoes, Lars, Hedelin, Per
• Primary Examiner(s): Vo, Huyen X
• Application Number:
  US16/376,433
• Publication Number:
  US 20190237052A1
• Time in Patent Office: 410 Days
• CPC Class Codes: G10H 1/0091 Means for obtaining special acoustic effects combined with modulation G10H1/043
• CPC Class Codes: G10H 1/125 using a digital filter
• CPC Class Codes: G10H 2210/311 Distortion, i.e. desired non-linear audio processing to change the tone color, e.g. by adding harmonics or deliberately distorting the amplitude of an audio waveform distortion functions G10H2250/201, G10H2250/205
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: G10L 21/0388 Details of processing therefor

Abstract

The present document relates to audio coding systems which make use of a harmonic transposition method for high frequency reconstruction (HFR), and to digital effect processors, e.g. so-called exciters, where generation of harmonic distortion adds brightness to the processed signal. In particular, a system configured to generate a high frequency component of a signal from a low frequency component of the signal is described. The system may comprise an analysis filter bank (501) configured to provide a set of analysis subband signals from the low frequency component of the signal; wherein the set of analysis subband signals comprises at least two analysis subband signals; wherein the analysis filter bank (501) has a frequency resolution of Δf. The system further comprises a nonlinear processing unit (502) configured to determine a set of synthesis subband signals from the set of analysis subband signals using a transposition order P; wherein the set of synthesis subband signals comprises a portion of the set of analysis subband signals phase shifted by an amount derived from the transposition order P; and a synthesis filter bank (504) configured to generate the high frequency component of the signal from the set of synthesis subband signals; wherein the synthesis filter bank (504) has a frequency resolution of FΔf; with F being a resolution factor, with F≥1; wherein the transposition order P is different from the resolution factor F.

Claims

1. A system configured to generate a high frequency component of a signal from a low frequency component of the signal, the system comprising:

an analysis filter bank configured to provide a set of analysis subband signals from the low frequency component of the signal;

wherein the set of analysis subband signals comprises at least two analysis subband signals;

a nonlinear processing unit configured to determine a set of synthesis subband signals from the set of analysis subband signals;

wherein the nonlinear processing unit is configured to determine an n^th synthesis subband signal of the set of synthesis subband signals from a k^th analysis subband signal and a (k+1)^th analysis subband signal of the set of analysis subband signals;

wherein a magnitude of the n^th synthesis subband signal depends on a transposition factor T; and

a synthesis filter bank configured to generate the high frequency component of the signal based on the set of synthesis subband signals.

2. The system of claim 1, wherein

the analysis filter bank has a number L_A of analysis subbands, with L_A>

1, where k is an analysis subband index with k=0, . . . , L_A−

1; and

the synthesis filter bank has a number L_S of synthesis subbands, with L_s>

1 L_S>

0, where n is a synthesis subband index with n=0, . . . , L_S−

1.

3. The system of claim 2, wherein the number L_A of analysis subbands is equal to the number L_S of synthesis subbands.

4. The system of claim 1, wherein

the analysis filter bank has a frequency resolution of Δ

f; and

the synthesis filter bank has a frequency resolution of FΔ

f;

with F being a resolution factor, with F≥

1.

5. The system of claim 1, further comprising:

a core decoder configured to convert an encoded bit stream into the low frequency component of the signal;

an analysis quadrature mirror filter bank, referred to as QMF bank, configured to convert the high frequency component into a plurality of QMF subband signals;

a high frequency reconstruction processing module configured to modify the QMF subband signals; and

a synthesis QMF bank configured to generate a modified high frequency component from the modified QMF subband signals.

6. A method for generating a high frequency component of a signal from a low frequency component of the signal, the method comprising:

providing a set of analysis subband signals from the low frequency component of the signal;

wherein the set of analysis subband signals comprises at least two analysis subband signals;

determining a set of synthesis subband signals from the set of analysis subband signals, such that an n^th synthesis subband signal of the set of synthesis subband signals is determined from a k^th analysis subband signal and a (k+1)^th analysis subband signal of the set of analysis subband signals;

wherein a magnitude of the n^th synthesis subband signal depends on a transposition factor T; and

generating the high frequency component of the signal based on the set of synthesis subband signals.

7. The method of claim 6, wherein

the set of analysis subband signals is generated from the low frequency component using an analysis filter bank;

and

the high frequency component is generated from the set of synthesis subband signals using a synthesis filter bank.

8. A non-transitory computer readable storage medium comprising a sequence of instructions, wherein, when executed by an audio signal processing device, the sequence of instructions causes the device to perform a method for generating a high frequency component of a signal from a low frequency component of the signal, the method comprising:

providing a set of analysis subband signals from the low frequency component of the signal;

wherein the set of analysis subband signals comprises at least two analysis subband signals;

determining a set of synthesis subband signals from the set of analysis subband signals, such that an n^th synthesis subband signal of the set of synthesis subband signals is determined from a k^th analysis subband signal and a (k+1)^th analysis subband signal of the set of analysis subband signals;

wherein a magnitude of the n^th synthesis subband signal depends on a transposition factor T; and

generating the high frequency component of the signal based on the set of synthesis subband signals.