Granted Patent B2

US 12,488,804 · App. 18/540,819 · Granted Dec 2, 2025

Inventors: Sascha Dick (Nuremberg, DE); Christian Helmrich (Erlangen, DE); Andreas Hoelzer (Erlangen, DE)

Assignee: Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.

G10L19/022G10L19/03G10L19/008G10L19/028

Abstract

Claims (50)

1 . An audio decoder, comprising an electronic circuit, programmed computer or microprocessor configured to:

extract a sequence of frequency-domain coefficients relating to a frame of an audio signal from a data stream;

extract scale factors for the frame from the data stream;

subject the frequency-domain coefficients, scaled according to the scale factors, to inverse transformation to obtain a time-domain portion of the audio signal corresponding to the frame;

subject the time-domain portion to an overlap-add process to obtain the audio signal,

wherein the audio decoder is responsive to a signalization within the data stream for the frame of the audio signal so as to, depending on the signalization,

form one transform out of the sequence of frequency-domain coefficients by maintaining a sequential order of the frequency-domain coefficients in the sequence of frequency-domain coefficients and subject the one transform, scaled according to the scale factors, to an inverse transformation of a first transform length, or

form more than one transform by de-interleaving the frequency-domain coefficients from the sequence of frequency-domain coefficients and subject, scaled according to the scale factors, each of the more than one transforms to an inverse transformation of a second transform length, shorter than the first transform length,

wherein the frequency-domain coefficients are grouped into a number of scale factor bands which is independent from the signalization, and a scale factor is extracted from the data stream for each scale factor band.

2 . The audio decoder of claim 1 , configured to use context-based entropy decoding to extract the sequence of frequency-domain coefficients from the data stream, with assigning, for each frequency-domain coefficient, a context to the respective frequency-domain coefficient in a manner independent from the signalization.

3 . The audio decoder of claim 1 , configured to subject the frequency-domain coefficients to scaling according to the scale factors at a spectral resolution independent from the signalization.

4 . The audio decoder of claim 1 , configured to subject the sequence of frequency-domain coefficients to noise filling, at a spectral resolution which is independent from the signalization.

5 . The audio decoder of claim 1 , configured to:

in the formation of the one transform, apply inverse temporal noise shaping filtering on the sequence of frequency-domain coefficients using the sequential order, and

in the formation of the more than one transforms, apply inverse temporal noise shaping filtering on the sequence of frequency-domain coefficients by de-interleaving the frequency-domain coefficients of the more than one transforms, concatenating of the more than one transforms spectrally transform-wise to yield a concatenation of the more than one transforms and applying the inverse temporal noise shaping filtering on the concatenation of the more than one transforms.

6 . The audio decoder of claim 1 , configured to support joint-stereo coding with or without inter-channel stereo prediction and to use the sequence of frequency-domain coefficients as a sum or difference spectrum or prediction residual of the inter-channel stereo prediction.

7 . The audio decoder of claim 1 , wherein the number of the more than one transforms equals 2, and the first transform length is twice the second transform length.

8 . The audio decoder of claim 1 , wherein the inverse transformation is an inverse modified discrete cosine transform (MDCT).

9 . An audio encoder, comprising an electronic circuit, programmed computer or microprocessor configured to:

subject time-domain portions of an audio signal to transformation to obtain, for each time-domain portion, frequency-domain coefficients;

inversely scale the frequency-domain coefficients according to scale factors,

wherein the audio encoder configured to switch, for a predetermined frame, between

performing one transform of a first transform length, and

performing more than one transform of a second transform length, shorter than the first transform length;

signal the switching for the predetermined frame by a signalization within the data stream for the predetermined frame,

wherein the audio encoder is configured to:

arrange, for the predetermined frame, the frequency-domain coefficients, inversely scaled according to scale factors, at a sequential order so as to obtain a sequence of frequency-domain coefficients by, depending on the signalization,

sequentially arranging the frequency-domain coefficients of the one transform in case of one transform performed for the respective frame, and

by interleaving the frequency-domain coefficients of the more than one transform of the respective frame in case of more than one transform performed for the respective frame, so that spectrally corresponding frequency-domain coefficients of the more than two transforms immediately follow each other; and

wherein the frequency-domain coefficients are grouped into a number of scale factor bands which is independent from the signalization, and a scale factor is inserted into the data stream for each scale factor band.

10 . A method for audio decoding, comprising:

extracting a sequence of frequency-domain coefficients relating to a frame of an audio signal from a data stream;

extracting scale factors for the frame from the data stream;

subjecting the frequency-domain coefficients, scaled according to scale factors, to inverse transformation to obtain a time-domain portion of the audio signal; and

subjecting the time-domain portion to an overlap-add process to obtain the audio signal,

wherein the subjection to inverse transformation is responsive to a signalization within the data stream for the frame so as to, depending on the signalization, comprise:

forming one transform out of the sequence of frequency-domain coefficients by maintaining a sequential order of the frequency-domain coefficients in the sequence of frequency-domain coefficients and subjecting the one transform, scaled according to the scale factors, to an inverse transformation of a first transform length, or

forming more than one transform by de-interleaving the frequency-domain coefficients from the sequence of frequency-domain coefficients and subjecting, scaled according to the scale factors, each of the more than one transforms to an inverse transformation of a second transform length, shorter than the first transform length,

wherein the frequency-domain coefficients are grouped into a number of scale factor bands which is independent from the signalization, and a scale factor is extracted from the data stream for each scale factor band.

11 . A method for audio encoding, comprising:

subjecting time-domain portions of an audio signal to transformation to obtain, for each time-domain portion, frequency-domain coefficients;

inversely scaling the frequency-domain coefficients according to scale factors;

switching for a predetermined frame between:

performing one transform of a first transform length, and

performing more than one transform of a second transform length, shorter than the first transform length;

signaling the switching by a signalization for the predetermined frame within the data stream;

arranging, for the predetermined frame, the frequency-domain coefficients, inversely scaled according to scale factors, at a sequential order so as to obtain a sequence of frequency-domain coefficients by, depending on the signalization,

sequentially arranging the frequency-domain coefficients of the one transform in case of one transform performed for the respective frame, and

by interleaving the frequency-domain coefficients of the more than one transform of the respective frame in case of more than one transform performed for the respective frame, so that spectrally corresponding frequency-domain coefficients of the more than two transforms immediately follow each other; and

wherein the frequency-domain coefficients are grouped into a number of scale factor bands which is independent from the signalization, and a scale factor is inserted into the data stream for each scale factor band.

Assignments (1)

Priority Claims (2)

Continuity (5)

References Cited (102)