Time Warp Contour Calculator, Audio Signal Encoder, Encoded Audio Signal Representation, Methods and Computer Program

• US 20110161088A1
• Filed: 07/01/2009
• Published: 06/30/2011
• Est. Priority Date: 07/11/2008
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Geiger, Ralf, Neuendorf, Max, Fuchs, Guillaume, Bayer, Stefan, Schuller, Derald, Disch, Sascha, Edler, Bernd
• Granted Patent: US 9,299,363 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G10L 21/04 Time compression or expansion

Abstract

A time warp contour calculator for use in an audio signal decoder is configured to receive an encoded warp ratio information, to derive a sequence of warp ratio values from the encoded warp ratio information, and to obtain warp contour node values starting from a time warp contour start value.

Ratios between the time warp contour node values and the time warp contour starting value are determined by the warp ratio values. The time warp contour calculator is configured to compute a time warp contour node value of a given time warp contour node, on the basis of a product-formation having a ratio between the time warp contour node value of the intermediate time warp contour node and the time warp contour starting value and a ratio between the time warp contour node value of the given time warp contour node and the time-warp contour node value of the intermediate time warp contour node as factors.

Claims

1. A time warp contour calculator for use in an audio signal decoder for providing a decoded audio signal representation on the basis of an encoded audio signal representation,

wherein the time warp contour calculator is configured to receive an encoded warp ratio information, to derive a sequence of warp ratio values from the encoded warp ratio information, and to acquire warp contour node values starting from a time warp contour start value,

wherein ratios between the time warp contour node values and the time warp contour starting value associated with a time warp contour start node are determined by the warp ratio values;

and

wherein the time warp contour calculator is configured to compute a time warp contour node value of a given time warp contour node, which is spaced from the time warp contour starting node by an intermediate time warp contour node on the basis of a product-formation comprising a ratio between the time warp contour node value of the intermediate time warp contour node and the time warp contour starting value and a ratio between the time warp contour node value of the given time warp contour node and the time-warp contour node value of the intermediate time warp contour node as factors.

2. The time warp contour calculator according to claim 1, wherein the time warp contour calculator is configured to periodically restart from the time warp contour starting value.

3. The time warp contour calculator according to claim 1, wherein the time warp contour calculator is configured to map the encoded warp ratio information onto a sequence of warp ratio values using a mapping rule,

wherein the mapping rule describes a mapping of a plurality of warp ratio codebook indices onto corresponding warp ratio values,

wherein the mapping rule is chosen such that the mapping rule comprises a plurality of pairs of reciprocal warp ratio values, such that product of two warp ratio values of a pair of reciprocal warp ratio values lies between 0.9997 and 1.0003.

4. The time warp contour calculator according to claim 1, wherein the time warp contour calculator is configured to map the encoded warp ratio information onto a sequence of warp ratio values using a mapping rule,

wherein the mapping rule describes a mapping of a plurality of warp ratio codebook indices onto corresponding warp ratio values,

wherein the mapping rule is chosen such that the warp ratio values, onto which the warp ratio codebook indices are mapped, are within a range between 0.97 and 1.03.

5. The time warp contour calculator according to claim 1, wherein the time warp contour calculator is configured to map the encoded warp ratio information onto a sequence of warp ratio values using a mapping rule,

wherein the mapping rule describes a mapping of a plurality of warp ratio codebook indices onto corresponding warp ratio values,

wherein the mapping rule is chosen asymmetrically such that a range of ascending warp ratio values is larger than a range of descending warp ratio values.

6. The time warp contour calculator according to claim 1, wherein the time warp contour calculator is configured to receive a side information indicating a non-varying time warp contour or a varying time warp contour for a given frame of the encoded audio signal representation, and, in dependence on the side information indicating a non-varying time warp contour or a varying time warp contour, to acquire the time warp contour node values for the given frame on the basis of the encoded warp ratio information, or to set the time warp contour node values for the given frame to the warp contour start value.

7. The time warp contour calculator according to claim 1, wherein the time warp contour calculator is configured to linearly interpolate between the time warp contour node values, to acquire time warp contour values of a new time warp contour portion.

8. The time warp contour calculator according to claim 1, wherein the time warp contour calculator is configured to iteratively acquire a sequence of time warp contour node values, wherein the time warp contour calculator is configured to acquire a subsequent time warp contour node value from a present time warp contour node value by multiplying the present time warp contour node value with a corresponding time warp ratio value.

9. An audio signal encoder for providing an encoded representation of an audio signal, the audio signal encoder comprising:

a time warp contour encoder configured to receive a time warp contour information associated with the audio signal, to compute a ratio between subsequent node values of the time warp contour, and to encode the ratio between subsequent node values of the time warp contour; and

a time warping signal encoder configured to acquire an encoded representation of a spectrum of the audio signal, taking into account a time warp described by the time warp contour information;

wherein the encoded representation of the audio signal comprises the encoded ratios and the encoded representation of the spectrum.

10. The audio signal encoder according to claim 9, wherein the time warp contour encoder is configured to check, whether a non-flat time warp contour is available for a given frame of the audio signal, and to set a flag within the encoded representation of the audio signal to indicate the absence of a varying time warp contour if a varying time warp contour is not available for the given frame of the audio signal, and

to omit an inclusion of encoded ratio values into the encoded representation of the audio signal if a varying time warp contour is not available for the given frame of the audio signal.

11. An encoded audio signal representation representing an audio signal, the audio signal representation comprising:

an encoded frequency domain representation representing one or more time warp resampled audio channels, resampled in accordance with a time warp; and

an encoded representation of a time warp contour representing the time warp, wherein the encoded representation of the time warp contour comprises a plurality of encoded time warp ratio values,

wherein the time warp ratio values represent ratios between subsequent node values of the time warp contour.

12. The encoded audio signal representation according to claim 11, wherein the encoded audio signal representation comprises, on a per-audio-frame basis, a flag indicating the presence of an encoded representation of a time warp contour for the respective frame.

13. A method for providing a decoded audio signal representation on the basis of an encoded audio signal representation, the method comprising:

receiving an encoded warp ratio information;

deriving a sequence of warp ratio values from the encoded warp ratio information; and

acquiring a plurality of time warp contour node values starting from a time warp contour start value,

wherein ratios between the time warp contour node values and the time warp contour starting value associated with the time warp contour starting node are determined by the warp ratio values;

wherein a time warp contour node value of a given time warp contour node, which is spaced from the time warp contour starting node by an intermediate time warp contour node, is computed on the basis of a product-formation, comprising a ratio between the time warp contour node value of the intermediate time warp contour node and the time warp contour starting value and a ratio between the time warp contour node value of the given time warp contour node and the time warp contour node value of the intermediate time warp contour node as factors.

14. A method for providing an encoded representation of an audio signal, the method comprising:

receiving a time warp contour information associated with the audio signal;

computing a ratio between subsequent node values of the time warp contour;

encoding the ratio between subsequent node values of the time warp contour; and

acquiring an encoded representation of a spectrum of the audio signal, taking into account a time warp described by the time warp contour information;

wherein the encoded representation of the audio signal comprises the encoded ratios and the encoded representation of the spectrum.

15. A computer program for performing a method for providing a decoded audio signal representation on the basis of an encoded audio signal representation, the method comprising:

receiving an encoded warp ratio information;

deriving a sequence of warp ratio values from the encoded warp ratio information; and

acquiring a plurality of time warp contour node values starting from a time warp contour start value, wherein ratios between the time warp contour node values and the time warp contour starting value associated with the time warp contour starting node are determined by the warp ratio values;

wherein a time warp contour node value of a given time warp contour node, which is spaced from the time warp contour starting node by an intermediate time warp contour node, is computed on the basis of a product-formation, comprising a ratio between the time warp contour node value of the intermediate time warp contour node and the time warp contour starting value and a ratio between the time warp contour node value of the given time warp contour node and the time warp contour node value of the intermediate time warp contour node as factors, when the computer program runs on a computer.

16. A computer program for performing a method for providing an encoded representation of an audio signal, the method comprising:

receiving a time warp contour information associated with the audio signal;

computing a ratio between subsequent node values of the time warp contour;

encoding the ratio between subsequent node values of the time warp contour; and

acquiring an encoded representation of a spectrum of the audio signal, taking into account a time warp described by the time warp contour information;

wherein the encoded representation of the audio signal comprises the encoded ratios and the encoded