Noise filling concept

• US 9,792,920 B2
• Filed: 07/29/2015
• Issued: 10/17/2017
• 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, Gayer, Marc, Helmrich, Christian, Markovic, Goran, Luis Valero, Maria
• Primary Examiner(s): Han, Qi
• Application Number:
  US14/812,354
• Publication Number:
  US 20150332689A1
• Time in Patent Office: 811 Days
• Field of Search: 704500, 704501, 704502
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/04 using predictive techniques

Abstract

Noise filling of a spectrum of an audio signal is improved in quality with respect to the noise filled spectrum so that the reproduction of the noise filled audio signal is less annoying, by performing the noise filling in a manner dependent on a tonality of the audio signal.

Claims

1. Apparatus configured to perform noise filling on a spectrum of an audio signal in a manner dependent on a tonality of the audio signal, wherein the apparatus is configured to:

dequantize the spectrum, as derived after the noise-filling, using a spectrally varying and signal-adaptive quantization step size controlled via a linear prediction spectral envelope signaled via linear prediction coefficients in a data stream into which the spectrum is coded, or scale factors relating to scale factor bands, signaled in the data stream into which the spectrum is coded,

identify contiguous spectral zero-portions of the audio signal'"'"'s spectrum and to apply the noise filling onto the contiguous spectral zero-portions identified, and

respectively fill the contiguous spectral zero-portions of the audio signal'"'"'s spectrum with noise spectrally shaped with a function having a local maximum surrounded by two outwardly falling flanks wherein the function is set dependent on a respective contiguous spectral zero-portion'"'"'s width so that the function is confined to the respective contiguous spectral zero-portion, and wherein a fill width at half maximum of the function is adjusted dependent on the tonality of the audio signal so that, if the tonality of the audio signal increases, the fill width at half maximum of the function gets more compact in an inner of the respective contiguous spectral zero-portion and distanced from the respective contiguous spectral zero-portion'"'"'s outer edges.

2. Apparatus according to claim 1, wherein the apparatus is configured to scale the noise with which the contiguous spectral zero-portions are filled using a scalar global noise level signaled in the data stream into which the spectrum is coded in a spectrally global manner.

3. Apparatus according to claim 1, wherein the apparatus is configured to generate the noise with which the contiguous spectral zero-portions are filled, using a random or pseudo-random process or using patching.

4. Apparatus according to claim 1, wherein the apparatus is configured to derive the tonality from a coding parameter coded within the data stream so that the dependency on the tonality involves a dependency on the coding parameter.

5. Apparatus according to claim 4, wherein the apparatus is configured such that the coding parameter is one of

an LTP (long-term prediction) flag or gain, and

a TNS (temporal noise shaping) enablement flag or gain, and

a spectrum rearrangement enablement flag signalling a coding option according to which quantized spectral values are spectrally re-arranged with additionally transmitting within the data stream the rearrangement prescription.

6. Apparatus according to claim 1, wherein the apparatus is configured to confine the performance of the noise filling onto a high-frequency spectral portion of the audio signal'"'"'s spectrum.

7. Apparatus according to claim 1, wherein the apparatus is configured to set a low-frequency starting position of the high-frequency spectral portion corresponding to an explicit signaling in the data stream.

8. Apparatus according to claim 1, wherein the apparatus is configured to, in performing the noise filling, fill contiguous spectral zero-portions of the spectrum with noise a level of which exhibits a decrease from low to high frequencies, approximating a spectral low-pass filter'"'"'s transfer function so as to counteract a spectral tilt caused by a pre-emphasis used to code the audio signal'"'"'s spectrum.

9. Apparatus according to claim 8, wherein the apparatus is configured to adapt a steepness of the decrease to a pre-emphasis factor of the pre-emphasis.

10. Audio decoder supporting noise filling comprising an apparatus according to claim 1.

11. Perceptual transform audio decoder comprising

an apparatus configured to perform noise filling on a spectrum of an audio signal according to claim 1;

and

a frequency domain noise shaper configured to subject the noise filled spectrum to spectral shaping using a spectral perceptual weighting function.

12. Audio encoder supporting noise filling comprising an apparatus according to claim 1, the encoder being configured to use a spectrum filled with noise by the apparatus, for analysis-by-synthesis.

13. Apparatus comprising a microprocessor configured to, an electronic circuit configured to, or a programmable computer programmed to:

perform noise filling on a spectrum of an audio signal in a manner dependent on a tonality of the audio signal by filling a contiguous spectral zero-portion of the audio signal'"'"'s spectrum with noise spectrally shaped by

a function having a local maximum surrounded by two outwardly falling flanks wherein the function is set dependent on a respective contiguous spectral zero-portion'"'"'s width so that the function is confined to the respective contiguous spectral zero-portion, and wherein a fill width at half maximum of the function is adjusted dependent on the tonality of the audio signal so that, if the tonality of the audio signal increases, the fill width at half maximum of the function gets more compact in an inner of the respective contiguous spectral zero-portion and distanced from the respective contiguous spectral zero-portion'"'"'s outer edges, and

dequantize the spectrum, as derived by the noise-filling, using

a spectrally varying and signal-adaptive quantization step size controlled via a linear prediction spectral envelope signaled via linear prediction coefficients in a data stream into which the spectrum is coded, or

scale factors relating to scale factor bands, signaled in the data stream into which the spectrum is coded.