Audio Signal Decoder, Time Warp Contour Data Provider, Method and Computer Program

• US 20110106542A1
• Filed: 07/01/2009
• Published: 05/05/2011
• 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, Schuller, Gerald, Neuendorf, Max, Disch, Sascha, Fuchs, Guillaume, Edler, Bernd, Bayer, Stefan
• Granted Patent: US 9,043,216 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

An audio signal decoder configured to provide a decoded audio signal representation on the basis of an encoded audio signal representation having a time warp contour evolution information has a time warp contour calculator, a time warp contour data rescaler and a warp decoder. The time warp contour calculator is configured to generate time warp contour data repeatedly restarting from a predetermined time warp contour start value on the basis of a time warp contour evolution information describing a temporal evolution of the time warp contour. The time warp contour data rescaler is configured to rescale at least a portion of the time warp contour data such that a discontinuity at a restart is avoided, reduced or eliminated in a rescaled version of the time warp contour. The warp decoder is configured to provide the decoded audio signal representation on the basis of the encoded audio signal representation and using the rescaled version of the time warp contour.

Claims

1. A audio signal decoder configured to provide a decoded audio signal representation on the basis of an encoded audio signal representation comprising a time warp contour evolution information, the audio signal decoder comprising:

a time warp calculator configured to generated time warp contour data repeatedly restarting from a predetermined time warp contour start value on the basis of the time warp contour evolution information describing a temporal evolution of the time warp contour;

a time warp contour rescaler configured to rescale at least a portion of the time warp contour data such that a discontinuity at a restart is avoided, reduced or eliminated in a rescaled version of the time warp contour; and

a warp decoder configured to provide the decoded audio signal representation on the basis of the encoded audio signal representation and using the resealed version of the time warp contour.

2. The audio signal decoder according to claim 1, wherein the time warp contour calculator is configured to calculate, starting from the predetermined starting value and using first a relative change information, a temporal evolution of a first portion of the time warp contour, and to calculate, starting from the predetermined starting value and using second relative change information, a temporal evolution of a second portion of the time warp contour, wherein the first portion of the time warp contour and the second portion of the time warp contour are subsequent portions of the time warp contour,

and wherein the time warp contour rescaler is configured to rescale one of the portions of the time warp contour, to acquire a steady transition between the first portion of the time warp contour and the second portion of the time warp contour.

3. The audio signal decoder according to claim 2, wherein the time warp contour rescaler is configured to rescale the first portion of the time warp contour such that a last value of the scaled version of the first time warp contour portion takes the predetermined starting value or deviates from the predetermined starting value by no more than a predetermined tolerance value.

4. The audio signal decoder according to claim 1, wherein the time warp contour rescaler is configured to multiply time warp contour data values with a normalization factor, to scale the portion of the time warp contour, or to divide time warp contour data values by a normalization factor to scale the portion of the time warp contour.

5. The audio signal decoder according to claim 1, wherein the time warp contour calculator is configured to acquire a warp contour sum value of a given portion of the time warp contour, and to scale the given portion of the time warp contour and the warp contour sum value of the given portion of the time warp contour using a common scaling value.

6. The audio signal decoder according to claim 1, wherein the audio signal decoder further comprises a time contour calculator configured to calculate a first time contour using time warp contour data values of a first portion of the time warp contour, of a second portion of the time warp contour and of a third portion of the time warp contour, and

to calculate a second time contour using time warp contour data values of the second portion of the time warp contour, of the third portion of the time warp contour and of a fourth portion of the time warp contour;

wherein the time warp contour calculator is configured to generate time warp contour data of the first portion of the time warp contour starting from a predetermined time warp contour start value on the basis of a time warp contour evolution information describing a temporal evolution of the first portion of the time warp contour;

wherein the time warp contour data rescaler is configured to rescale the first portion of the time warp contour such that a last value of the first portion of the time warp contour comprises the predetermined time warp contour start value;

wherein the time warp contour calculator is configured to generate warp contour data of the second portion of the time warp contour starting from the predetermined time warp contour start value on the basis of a time warp contour evolution information describing a temporal evolution of the second portion of the time warp contour;

wherein the time warp contour data rescaler is configured to jointly rescale the first portion of the time warp contour and the second portion of the time warp contour using a common scaling factor, such that a last value of the second portion of the time warp contour comprises the predetermined time warp contour start value, to acquire jointly a resealed time warp contour data values;

wherein the time warp contour calculator is configured to generate original time warp contour data values of the third portion of the time warp contour starting from the predetermined time warp contour start value, on the basis of a time warp contour evolution information of the third portion of the time warp contour;

wherein the time contour calculator is configured to calculate the first time contour using the jointly resealed time warp contour data values of the first and second time warp contour portions and the time warp contour data values of the third time warp contour portion;

wherein the time warp contour data rescaler is configured to jointly rescale time warp contour data values of the second, resealed portion of the time warp contour and of the third portion of the time warp contour using another common scaling factor, such that a last value of the third portion of the time warp contour comprises the predetermined time warp contour start value, to acquire a twice resealed version of the second portion of the time warp contour and a once resealed version of the third portion of the time warp contour;

wherein the time warp contour calculator is configured to generate original time warp contour data values of the fourth portion of the time warp contour starting from the predetermined time warp contour start value on the basis of a time warp contour evolution information of the fourth portion of the time warp contour; and

wherein the time contour calculator is configured to calculate the second time contour using the twice resealed version of the second portion of the time warp contour, the once resealed version of the third portion of the time warp contour and the original version of the fourth portion of the time warp contour.

7. The audio signal decoder according to claim 1, wherein the audio signal decoder comprises a time warp control information calculator configured to calculate a time warp control information using a plurality of portions of the time warp contour,

wherein the time warp control information calculator is configured to calculate a time warp control information for a reconstruction of a first frame of the audio signal on the basis of time warp contour data of a first plurality of time warp contour portions, and to calculate a time warp control information for a reconstruction of a second frame of the audio signal, which is overlapping or non-overlapping with the first frame of the audio signal, on the basis of time warp contour data of a second plurality of time warp contour portions,

wherein the first plurality of time warp contour portions is shifted, with respect to time, when compared to the second plurality of time warp contour portions, and

wherein the first plurality of time warp contour portions comprises at least one common time warp contour portion with the second plurality of time warp contour portions.

8. The audio signal decoder according to claim 7, wherein the time warp contour calculator is configured to generate the time warp contour such that the time warp contour restarts from the predetermined time warp contour start value at a position within the first plurality of time warp contour portions, or at a position within the second plurality of time warp contour portions, such that there is a discontinuity of the time warp contour at the location of the restart;

and

wherein the time warp contour rescaler is configured to rescale one or more of the time warp contour portions, such that the discontinuity is reduced or eliminated.

9. The audio signal decoder according to claim 8, wherein the time warp contour calculator is configured to generate the time warp contour such that there is a first restart of the time warp contour from the predetermined time warp contour start value at a position within the first plurality of time warp contour portions, such that there is a first discontinuity at the position of the first restart,

wherein the time warp contour rescaler is configured to rescale the time warp contour such that the first discontinuity is reduced,

wherein the time warp contour calculator is configured to also generate the time warp contour such that there is a second restart of the time warp contour from the predetermined time warp contour start value at a position within the second plurality of time warp contour portions, such that there is a second discontinuity at the position of the second restart;

and

wherein the time warp contour data rescaler is configured to also rescale the time warp contour such that the second discontinuity is reduced or eliminated.

10. The audio signal decoder according to claim 1, wherein the time warp contour calculator is configured to periodically restart the time warp contour starting from the predetermined time warp contour start value, such that there are periodic discontinuities at the restarts;

wherein the time warp contour data rescaler is adapted to successively rescale at least one portion of the time warp contour at any one time, to reduce successively or eliminate the discontinuities of the time warp contour at the restarts; and

wherein the audio signal decoder comprises a time warp control information calculator configured to combine time warp contour data from before and after the restart to acquire a time warp control information.

11. The audio signal decoder according to claim 1, wherein the time warp contour calculator is configured to receive an encoded warp ratio information, to derive a sequence of time warp ratio values from the encoded time warp ratio information, and to acquire time warp contour node values starting from the time warp contour start value;

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

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 starting value and the time warp contour node value of the intermediate time warp contour node and a ratio between the time warp contour node value of the intermediate time warp contour node and the time warp contour node value of the given time warp contour node as factors.

12. A method for providing a decoded audio signal representation on the basis of an encoded audio signal representation comprising a time warp contour evolution information, the method comprising:

generating time warp contour data repeatedly restarting from a predetermined time warp contour start value on the basis of a time warp contour evolution information describing a temporal evolution of the time warp contour;

rescaling at least a portion of the time warp contour data, such that a discontinuity at a restart is avoided, reduced or eliminated in a rescaled version of the time warp contour; and

providing the decoded audio signal representation on the basis of the encoded audio signal representation and using the resealed version of the time warp contour.

13. A computer program for performing the method according to claim 12, when the computer program runs on a computer.

14. A time warp contour data provider for providing time warp contour data representing a temporal evolution of a relative pitch of an audio signal on the basis of a time warp contour evolution information, the time warp contour data provider comprising:

a time warp contour calculator configured to generate time warp contour data on the basis of a time warp contour evolution information describing a temporal evolution of the time warp contour, wherein the time warp contour calculator is configured to repeatedly or periodically restart, at a restart position, a calculation of the time warp contour data from a predetermined time warp contour start value, thereby creating discontinuities of the time warp contour and reducing a range of the time warp contour data values; and

a time warp contour rescaler configured to repeatedly rescale portions of the time warp contour, to reduce or eliminate the discontinuities at the restart positions in resealed sections of the time warp contour.