# US 11,993,817 B2 · Oversampling in a combined transposer filterbank

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,993,817 B2
- Document ID: US11993817B2
- Status: Granted
- Kind: B2
- Application number: 18/156,701
- Filed: 2023-01-19
- Published: 2023-05-25
- Granted: 2024-05-28
- Earliest claimed: 2009-10-21
- Assignees: Dolby International AB
- Applicants: Dolby International AB
- Inventors: Lars Villemoes; Per Ekstrand
- Web page: https://patentgrep.com/patent/US11993817B2

## CPC

- C12Q 1/6883: for diseases caused by alterations of genetic material
- G10L 19/0204: {using subband decomposition}
- G10L 19/022: Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
- G10L 19/265: {Pre-filtering, e.g. high frequency emphasis prior to encoding}
- G10L 21/038: using band spreading techniques
- C12Q 2600/118: Prognosis of disease development
- C12Q 2600/156: Polymorphic or mutational markers
- C12Q: MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS (immunoassay G01N33/53); COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

The present invention relates to coding of audio signals, and in particular to high frequency reconstruction methods including a frequency domain harmonic transposer. A system and method for generating a high frequency component of a signal from a low frequency component of the signal is described. The system comprises an analysis filter bank (501) comprising an analysis transformation unit (601) having a frequency resolution of Δf; and an analysis window (611) having a duration of DA; the analysis filter bank (501) being configured to provide a set of analysis subband signals from the low frequency component of the signal; a nonlinear processing unit (502, 650) configured to determine a set of synthesis subband signals based on a portion of the set of analysis subband signals, wherein the portion of the set of analysis subband signals is phase shifted by a transposition order T; and a synthesis filter bank (504) comprising a synthesis transformation unit (602) having a frequency resolution of QΔf; and a synthesis window (612) having a duration of DS; the synthesis filter bank (504) being configured to generate the high frequency component of the signal from the set of synthesis subband signals; wherein Q is a frequency resolution factor with Q≥1 and smaller than the transposition order T; and wherein the value of the product of the frequency resolution Δf and the duration DA of the analysis filter bank is selected based on the frequency resolution factor Q.

## Claims

### Claim 1

A system for generating an output audio signal comprising a high frequency component from an input audio signal comprising a low frequency component using a transposition order T, comprising:
an analysis window unit configured to apply an analysis window of a length of LA samples, thereby extracting a frame of the input signal;
an analysis transformation unit of order M and having a frequency resolution Δf configured to transform the LA samples into M complex coefficients;
a nonlinear processing unit, configured to modify phases of the complex coefficients based on the transposition order T, and to modify magnitudes of the complex coefficients based on the transposition order T;
a synthesis transformation unit of order M and having a frequency resolution QΔf, configured to transform the altered coefficients into M altered samples; wherein Q is a frequency resolution factor independent of the transposition order T; and
a synthesis window unit configured to apply a synthesis window of a length of Ls samples to the M altered samples, thereby generating a frame of the output signal;
wherein LA is equal to LS and M is equal to (QLA+Ls)/2.

### Claim 2

A method for generating an output audio signal comprising a high frequency component from an input audio signal comprising a low frequency component using a transposition order T, the method comprising:
applying an analysis window of a length of LA samples, thereby extracting a frame of the input signal;
transforming the frame of LA samples of the input signal into M complex coefficients using an analysis transformation of order M and frequency resolution Δf;
modifying phases of the complex coefficients based on the transposition order T, and modifying magnitudes of the complex coefficients based on the transposition order T;
transforming the altered coefficients into M altered samples using a synthesis transformation of order M and frequency resolution QΔf; wherein Q is a frequency resolution factor independent of the transposition order T; and
applying a synthesis window of a length of Ls samples to the M altered samples, thereby generating a frame of the output signal;
wherein LA is equal to LS and M is equal to (QLA+Ls)/2.

### Claim 3

A non-transitory computer-readable storage medium comprising a sequence of instructions, wherein, when executed by one or more processors, the sequence of instructions causes the one or more processors to perform a method for generating an output audio signal comprising a high frequency component from an input audio signal comprising a low frequency component using a transposition order T, the method comprising:
applying an analysis window of a length of LA samples, thereby extracting a frame of the input signal;
transforming the frame of LA samples of the input signal into M complex coefficients using an analysis transformation of order M and frequency resolution Δf;
modifying phases of the complex coefficients by using the transposition order T, and modifying magnitudes of the complex coefficients based on the transposition order T;
transforming the altered coefficients into M altered samples using a synthesis transformation of order M and frequency resolution QΔf; wherein Q is a frequency resolution factor independent of the transposition order T; and
applying a synthesis window of a length of Ls samples to the M altered samples, thereby generating a frame of the output signal;
wherein LA is equal to LS and M is equal to (QLA+Ls)/2.