APPARATUS AND METHOD FOR GENERATING A FREQUENCY ENHANCED SIGNAL USING TEMPORAL SMOOTHING OF SUBBANDS

• US 20150332697A1
• Filed: 07/29/2015
• Published: 11/19/2015
• Est. Priority Date: 01/29/2013
• 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: DISCH, Sascha, GEIGER, Ralf, HELMRICH, Christian, MULTRUS, Markus, SCHMIDT, Konstantin
• Granted Patent: US 9,741,353 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 2019/0012 Smoothing of parameters of the decoder interpolation
• CPC Class Codes: G10L 2019/0016 Codebook for LPC parameters
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: G10L 21/0388 Details of processing therefor
• CPC Class Codes: G10L 25/18 the extracted parameters being spectral information of each sub-band

Abstract

An apparatus for generating a frequency enhancement signal has: a signal generator for generating an enhancement signal from a core signal, the enhancement signal having an enhancement frequency range not included in the core signal, wherein a current time portion of the enhancement signal or the core signal has subband signals for a plurality of subbands; a controller for calculating the same smoothing information for the plurality of subband signals of the enhancement frequency range or the core signal, and wherein the signal generator is configured for smoothing the plurality of subband signals of the enhancement frequency range or the core signal using the same smoothing information.

Claims

1. An apparatus for generating a frequency enhancement signal, comprising:

a signal generator for generating an enhancement signal from a core signal, the enhancement signal comprising an enhancement frequency range not comprised in the core signal, wherein a current time portion of the enhancement signal or the core signal comprises subband signals for a plurality of subbands; and

a controller for calculating the same smoothing information for the plurality of subband signals of the enhancement frequency range or the core signal, and

wherein the signal generator is configured for smoothing the plurality of subband signals of the enhancement frequency range or the core signal using the same smoothing information, wherein the controller is configured to calculate the smoothing information using a combined energy of the plurality of subband signals of the core signal and the frequency enhancement signal or using only the frequency enhancement signal of the current time portion, and

using an average energy of the plurality of subband signals of the core signal and the frequency enhancement signal or of the core signal only of one or more earlier time portions preceding the current time portion or one or more later time portions following the current time portion.

2. The apparatus of claim 1,

wherein the smoothing information is a single correction factor for the plurality of subband signals of the enhancement frequency range, and wherein the signal generator is configured to apply the correction factor to the plurality of subband signals of the enhancement frequency range.

3. The apparatus in accordance with claim 1,

further comprising a filterbank or a provider for providing the plurality of subband signals of the core signal for a plurality of time-subsequent filterbank slots,

wherein the signal generator is configured to derive the plurality of subband signals of the enhancement frequency range for the plurality of time-subsequent filterbank slots using the plurality of subband signals of the core signal, and

wherein the controller is configured to calculate an individual smoothing information for each filterbank slot.

4. The apparatus in accordance with claim 1,

wherein the controller is configured to calculate a smoothing intensity control value based on the core signal or the frequency enhancement signal of the current time portion and one or more preceding time portions, and

wherein the controller is configured to calculate the smoothing information using the smoothing control value in such a way that the smoothing intensity varies dependent on a difference between an energy of the core signal or the frequency enhancement signal in a current time portion and an average energy in the core signal or the frequency enhancement signal of one or more preceding time portions.

5. The apparatus in accordance with claim 1,

wherein the controller is configured to calculate the smoothing information based on the following equation:

6. The apparatus in accordance with claim 1, wherein the signal generator is configured for shaping the core signal or the enhancement signal in addition to smoothing.

7. The apparatus of claim 6,

wherein the current time portion and at least one further time portion form a frame,

wherein the signal generator is configured for applying the same shaping information for a whole frame, and wherein the signal generator is configured for smoothing using an individual smoothing information for each time portion within the frame.

8. The apparatus in accordance with claim 1,

wherein the signal generator is configured for performing an energy limitation on the frequency enhancement signal or the core signal in order to make sure that a signal acquired by a synthesis filterbank is so that an energy of a higher band is, at the most, equal to an energy in a lower band or greater than, at the most, by a predefined threshold of 3 dB or less.

9. The apparatus in accordance with claim 1,

wherein the signal generator is configured for mirroring a single subband signal of the core signal or the plurality of subband signals of the core signal when calculating the plurality of subband signals of the frequency enhancement signal.

11. A system for processing audio signals, comprising:

an encoder for generating an encoded core signal; and

an apparatus for generating a frequency enhancement signal of claim 1.

10. A method of generating a frequency enhancement signal, comprising:

generating an enhancement signal from a core signal, the enhancement signal comprising an enhancement frequency range not comprised in the core signal,

wherein a current time portion of the enhancement signal or the core signal comprises subband signals for a plurality of subbands;

calculating the same smoothing information for the plurality of subband signals of the enhancement frequency range or the core signal, and

wherein the generating comprises smoothing the plurality of subband signals of the enhancement frequency range or the core signal using the same smoothing information,

wherein the calculating comprises calculating the smoothing information using a combined energy of the plurality of subband signals of the core signal and the frequency enhancement signal or using only the frequency enhancement signal of the current time portion, and

using an average energy of the plurality of subband signals of the core signal and the frequency enhancement signal or of the core signal only of one or more earlier time portions preceding the current time portion or one or more later time portions following the current time portion.

12. A method of processing audio signals, comprising:

generating an encoded core signal; and

generating a frequency enhancement signal using a method of claim 10.

13. A computer program for performing, when running on a computer or a processor, the method of claim 10.

14. A computer program for performing, when running on a computer or a processor, the method of claim 12.