Encoder, decoder and methods for signal-adaptive switching of the overlap ratio in audio transform coding

Patent metadata

Field	Value
Publication number	US-10770084-B2
Application number	US-201815933149-A
Country	US
Kind code	B2
Filing date	Mar 22, 2018
Priority date	Sep 25, 2015
Publication date	Sep 8, 2020
Grant date	Sep 8, 2020

Abstract

A decoder for decoding a plurality of spectral-domain audio samples is provided. The decoder includes a first decoding module for generating a first group and a second group of time-domain intermediate audio samples from the spectral-domain audio samples. Moreover, the decoder includes an overlap-adder for overlap-adding the first group of time-domain intermediate audio samples with an overlap of more than 5% and at most 50% with the second group of time-domain intermediate audio samples. Furthermore, the decoder includes a second decoding module for generating a third group and a fourth group of time-domain intermediate audio samples from the spectral-domain audio samples. Moreover, the decoder includes an output interface.

First claim

The invention claimed is:

1. A decoder for decoding a plurality of spectral-domain audio samples, wherein the decoder comprises:
a first decoding module for decoding a first group of the spectral-domain audio samples by generating a first group of time-domain intermediate audio samples from the spectral-domain audio samples of the first group of the spectral-domain audio samples, and for decoding a second group of the spectral-domain audio samples by generating a second group of time-domain intermediate audio samples from the spectral-domain audio samples of the second group of the spectral-domain audio samples,
an overlap-adder, wherein the overlap-adder is configured to conduct overlap-adding of exactly two groups of time-domain intermediate audio samples, said exactly two groups being the first group and the second group of time-domain intermediate audio samples, wherein the overlap-adder is configured to overlap-add said exactly two groups with an overlap of more than 5% and at most 50%, wherein said overlap-add of said exactly two groups results in generating a first plurality of time-domain audio output samples of an audio signal,
a second decoding module for decoding a third group of the spectral-domain audio samples by generating a third group of time-domain intermediate audio samples from the spectral-domain audio samples of the third group of the spectral-domain audio samples, and for decoding a fourth group of the spectral-domain audio samples by generating a fourth group of time-domain intermediate audio samples from the spectral-domain audio samples of the fourth group of the spectral-domain audio samples, and
an output interface for outputting the first plurality of time-domain audio output samples of the audio signal, a second plurality of time-domain audio output samples of the audio signal and a third plurality of time-domain audio output samples of the audio signal,
wherein the overlap-adder is configured to acquire the second plurality of time-domain audio output samples using overlap-adding at least the third group of time-domain intermediate audio samples with an overlap of more than 60% and less than 100% with the fourth group of time-domain intermediate audio samples, and
wherein the overlap-adder is configured to acquire the third plurality of time-domain audio output samples using overlap-adding of at least the second group of time-domain intermediate audio samples with the third group of time-domain intermediate audio samples, or wherein the overlap-adder is configured to acquire the third plurality of time-domain audio output samples using overlap-adding of at least the fourth group of time-domain intermediate audio samples with the first group of time-domain intermediate audio samples.

2. The decoder according to claim 1 ,
wherein the first plurality of time-domain audio output samples of the audio signal precedes the third plurality of time-domain audio output samples of the audio signal in time, and wherein the third plurality of time-domain audio output samples of the audio signal precedes the second plurality of time-domain audio output samples of the audio signal in time, and wherein the overlap-adder is configured to acquire the third plurality of time-domain audio output samples using overlap-adding of at least the second group of time-domain intermediate audio samples with the third group of time-domain intermediate audio samples, or
wherein the second plurality of time-domain audio output samples of the audio signal precedes the third plurality of time-domain audio output samples of the audio signal in time, and wherein the third plurality of time-domain audio output samples of the audio signal precedes the first plurality of time-domain audio output samples of the audio signal in time, and wherein the overlap-adder is configured to acquire the third plurality of time-domain audio output samples using overlap-adding of at least the second group of time-domain intermediate audio samples with the third group of time-domain intermediate audio samples.

3. The decoder according to claim 1 ,
wherein the overlap-adder is configured to overlap-add the first group of time-domain intermediate audio samples with an overlap of exactly 50% with the second group of time-domain intermediate audio samples, and
wherein the overlap-adder is configured to overlap-add at least the third group of time-domain intermediate audio samples with an overlap of at least 75% and less than 100% with the fourth group of time-domain intermediate audio samples.

4. The decoder according to claim 3 ,
wherein the first decoding module is configured to conduct an inverse Modified Discrete Cosine Transform or an inverse Modified Discrete Sine Transform, and
wherein the second decoding module is configured to conduct an inverse Extended Lapped Transform or an inverse Modified Extended Lapped Transform.

5. The decoder according to claim 3 , wherein the overlap-adder is configured to overlap-add at least the third group of time-domain intermediate audio samples with an overlap of exactly 75% with the fourth group of time-domain intermediate audio samples.

6. The decoder according to claim 1 ,
wherein a first number of time-domain intermediate audio samples of the first group of time-domain intermediate audio samples is equal to a second number of time-domain intermediate audio samples of the second group of time-domain intermediate audio samples,
wherein a third number of time-domain intermediate audio samples of the third group of time-domain intermediate audio samples is equal to a fourth number of time-domain intermediate audio samples of the fourth group of time-domain intermediate audio samples,
wherein the second number is equal to the third number divided by 2, and wherein the first number is equal to the fourth number divided by 2.

7. The decoder according to claim 1 ,
wherein the second decoding module is configured to decode a fifth group of the spectral-domain audio samples by generating a fifth group of time-domain intermediate audio samples from the spectral-domain audio samples of the fifth group of the spectral-domain audio samples, and for decoding a sixth group of the spectral-domain audio samples by generating a sixth group of time-domain intermediate audio samples from the spectral-domain audio samples of the sixth group of the spectral-domain audio samples, and
wherein the overlap-adder is configured to acquire the second plurality of time-domain audio output samples by overlap-adding the third group of time-domain intermediate audio samples and the fourth group of time-domain intermediate audio samples and the fifth group of time-domain intermediate audio samples and the sixth group of time-domain intermediate audio samples, such that the third or the fourth group of time-domain intermediate audio samples overlaps with at least 75% and less than 100% with the fifth group of time-domain intermediate audio samples, and such that the fifth group of time-domain intermediate audio samples overlaps with at least 75% and less than 100% with the sixth group of time-domain intermediate audio samples.

8. The decoder according to claim 1 ,
wherein the second decoding module is configured to generate at least one of the third group of time-domain intermediate audio samples and the fourth group of time-domain intermediate audio samples depending on
cs ( a ( n+b )( k+c )),

wherein cs( ) is cos( ) or sin( ),
wherein n indicates a time index of one of the time-domain intermediate audio samples of the third or the fourth group of time-domain intermediate audio samples,
wherein k indicates a spectral index of one of the spectral-domain audio samples of the first or the second or the third or the fourth group of the spectral-domain audio sa

Assignees

• Fraunhofer Ges Forschung

Inventors

• Helmrich Christian
• Edler Bernd
• Schwegler Tobias
• Schuh Florian

Classifications

• G06F17/11

  for solving equations {, e.g. nonlinear equations, general mathematical optimization problems (optimization specially adapted for a specific administrative, business or logistic context G06Q10/04)} · CPC title

• G10L19/022 Primary

  Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring · CPC title

• G06F17/147

  Discrete orthonormal transforms, e.g. discrete cosine transform, discrete sine transform, and variations therefrom, e.g. modified discrete cosine transform, integer transforms approximating the discrete cosine transform (G06F17/145 takes precedence) · CPC title

• G10L19/02

  using spectral analysis, e.g. transform vocoders or subband vocoders · CPC title

• G10L19/0212

  using orthogonal transformation · CPC title