Apparatus and method for processing an input audio signal using cascaded filterbanks

Patent metadata

Field	Value
Publication number	US-12308036-B2
Application number	US-202318397158-A
Country	US
Kind code	B2
Filing date	Dec 27, 2023
Priority date	Mar 9, 2010
Publication date	May 20, 2025
Grant date	May 20, 2025

Abstract

An apparatus for processing an input audio signal relies on a cascade of filterbanks, the cascade having a synthesis filterbank for synthesizing an audio intermediate signal from the input audio signal, the input audio signal being represented by a plurality of first subband signals generated by an analysis filterbank, wherein a number of filterbank channels of the synthesis filterbank is smaller than a number of channels of the analysis filterbank. The apparatus furthermore has a further analysis filterbank for generating a plurality of second subband signals from the audio intermediate signal, wherein the further analysis filterbank has a number of channels being different from the number of channels of the synthesis filterbank, so that a sampling rate of a subband signal of the plurality of second subband signals is different from a sampling rate of a first subband signal of the plurality of first subband signals.

First claim

What is claimed is:

1. Apparatus for resampling an audio signal, comprising
a first filter bank for generating a plurality of subband signals from the audio signal, wherein a sampling rate of the subband signals is smaller than a sampling rate of the audio signal;
at least one synthesis filter bank followed by an analysis filter bank for performing a sample rate conversion to obtain a sample rate converted signal, the synthesis filter bank having a number of channels different from a number of channels of the analysis filter bank, wherein the at least one synthesis filter bank has a synthesis filter bank output, wherein the analysis filter bank has an analysis filter bank input, and wherein the synthesis filter bank output is connected to the analysis filter bank input;
a time stretch processor for processing the sample rate converted signal to obtain a time stretched signal; and
a combiner for combining the time stretched signal and a low-band signal or a different time stretched signal.

2. Apparatus of claim 1 ,
wherein the audio signal is a core decoded audio signal,
wherein the first filter bank is an M-band analysis filter bank, and
wherein the at least one synthesis filter bank is a subsampled synthesis filter bank having a decreased number of subbands.

3. Apparatus of claim 1 ,
wherein the time stretch processor comprises a block extractor, is configured for performing a non-linear processing and a windowing, and comprises an overlap/add unit.

4. Apparatus of claim 1 ,
wherein the first filter bank has 32 bands,
wherein a sampling rate of the subband signals is 1/32 of a sampling rate of the audio signal,
wherein the at least one synthesis filter bank has Q 2 bands, Q 2 being an integer,
wherein the analysis filter bank has 2Q 2 bands, so that a sampling rate of subband signals output by the analysis filter bank is 1/64 of the sampling rate of the audio signal, and
wherein the time stretch processor is configured to perform a factor 2 stretch, so that the time stretched signal has a sampling rate equal to 1/32 of the sampling rate of the audio signal.

5. Apparatus of claim 1 , wherein the first filter bank, the at least one synthesis filter bank, and the analysis filter bank are QMF filter banks.

6. Method for resampling an audio signal, comprising:
generating, using a first filter bank, a plurality of subband signals from the audio signal, wherein a sampling rate of the subband signals is smaller than a sampling rate of the audio signal;
performing a sample rate conversion using at least one synthesis filter bank followed by an analysis filter bank to obtain a sample rate converted signal, the at least one synthesis filter bank having a number of channels different from a number of channels of the analysis filter bank, wherein the at least one synthesis filter bank has a synthesis filter bank output, wherein the analysis filter bank has an analysis filter bank input, and wherein a signal at the synthesis filter bank output is fed into to the analysis filter bank input;
processing, using a time stretch processor, the sample rate converted signal to obtain a time stretched signal; and
combining the time stretched signal and a low-band signal or a different time stretched signal.

7. Non-transitory storage medium having stored thereon a computer program for performing, when running on a computer, a method for resampling an audio signal, the method comprising:
generating, using a first filter bank, a plurality of subband signals from the audio signal, wherein a sampling rate of the subband signals is smaller than a sampling rate of the audio signal;
performing a sample rate conversion using at least one synthesis filter bank followed by an analysis filter bank to obtain a sample rate converted signal, the at least one synthesis filter bank having a number of channels different from a number of channels of the analysis filter bank, wherein the at least one synthesis filter bank has a synthesis filter bank output, wherein the analysis filter bank has an analysis filter bank input, and wherein a signal at the synthesis filter bank output is fed into to the analysis filter bank input;
processing, using a time stretch processor, the sample rate converted signal to obtain a time stretched signal; and
combining the time stretched signal and a low-band signal or a different time stretched signal.

Assignees

• Fraunhofer Ges Forschung
• Dolby Int Ab

Inventors

• Villemoes Lars
• Ekstrand Per
• Disch Sascha
• Nagel Frederik
• Wilde Stephan

Classifications

• G10L19/0204 Primary

  using subband decomposition · CPC title

• G10L21/04

  Time compression or expansion · CPC title

• G10L21/038

  using band spreading techniques · CPC title

• G10L19/008 Primary

  Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing · CPC title

• G10L21/0232 Primary

  Processing in the frequency domain · CPC title