Audio encoder, audio decoder, method for providing an encoded audio information, method for providing a decoded audio information, computer program and encoded representation using a signal-adaptive bandwidth extension

Patent metadata

Field	Value
Publication number	US-9646624-B2
Application number	US-201514811727-A
Country	US
Kind code	B2
Filing date	Jul 28, 2015
Priority date	Jan 29, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

An audio encoder has a low frequency encoder which encodes a low frequency portion of the input audio information to obtain an encoded representation of the low frequency portion, and a bandwidth extension information provider which provides bandwidth extension information. The audio encoder is configured to selectively include bandwidth extension information into the encoded audio information in a signal-adaptive manner. An audio decoder has a low frequency decoder which decodes an encoded representation of a low frequency portion to obtain a decoded representation of the low frequency portion, and a bandwidth extension which obtains a bandwidth extension signal using a blind bandwidth extension for portions of an audio content for which no bandwidth extension parameters are included in the encoded audio information, and which obtains the bandwidth extension signal using a parameter-guided bandwidth extension for portions of the audio content for which bandwidth extension parameters are included in the encoded audio information.

First claim

The invention claimed is:

1. An audio encoder for providing an encoded audio information on the basis of an input audio information, the audio encoder comprising:
a low frequency encoder configured to encode a low frequency portion of the input audio information to acquire an encoded representation of the low frequency portion; and
a bandwidth extension information provider configured to provide bandwidth extension information on the basis of the input audio information;
wherein the audio encoder is configured to selectively include bandwidth extension information into the encoded audio information in a signal-adaptive manner;
wherein the audio encoder comprises a detector configured to identify portions of the input audio information for which bandwidth extension parameters cannot be estimated on the basis of the low frequency portion with a sufficient or desired accuracy; and
wherein the audio encoder is configured to selectively include bandwidth extension information into the encoded audio information for portions of the input audio information identified by the detector.

2. The audio encoder according to claim 1 , wherein the audio encoder is configured to identify portions of the input audio information which cannot be decoded with a sufficient or desired quality on the basis of the encoded representation of the low-frequency portion, and using a blind bandwidth extension; and
wherein the audio encoder is configured to selectively include bandwidth extension information into the encoded audio information for identified portions of the input audio information which cannot be decoded with a sufficient or desired quality on the basis of the encoded representation of the low-frequency portion, and using a blind bandwidth extension.

3. The audio encoder according to claim 1 , wherein the audio encoder is configured to identify portions of the input audio information in dependence on whether the portions are temporally stationary portions and in dependence on whether the portions comprise a low-pass character; and
wherein the audio encoder is configured to selectively omit an inclusion of bandwidth extension information into the encoded audio information for portions of the input audio information identified as temporally stationary portions comprising a low-pass character.

4. The audio encoder according to claim 3 , wherein the audio encoder is configured to identify portions of the input audio information in dependence on whether the portions comprise voiced speech, and/or in dependence on whether the portions comprise environmental noise, and/or in dependence on whether the portions comprise music without percussive instrumentation.

5. The audio encoder according to claim 1 , wherein the audio encoder is configured to identify portions of the input audio information in dependence on whether a difference between a spectral envelope of a low frequency portion and a spectral envelope of a high frequency portion is larger than or equal to a predetermined difference measure; and
wherein the audio encoder is configured to selectively include bandwidth extension information into the encoded audio information for portions of the input audio information identified in dependence on whether a difference between a spectral envelope of a low frequency portion and a spectral envelope of a high frequency portion is larger than or equal to a predetermined difference measure.

6. The audio encoder according to claim 5 , wherein the audio encoder is configured to identify portions in dependence on whether the portions comprise unvoiced speech, and/or wherein the audio encoder is configured to identify portions in dependence on whether the portions comprise percussive sounds.

7. The audio encoder according to claim 1 , wherein the audio encoder is configured to determine a spectral tilt of portions of the input audio information, and to identify portions of the input audio information in dependence on whether the determined spectral tilt is larger than or equal to a fixed or variable tilt threshold value; and
wherein the audio encoder is configured to selectively include bandwidth extension information into the encoded audio information for portions of the input audio information identified in dependence on whether the determined spectral tilt is larger than or equal to a fixed or variable tilt threshold.

8. The audio encoder according to claim 7 , wherein the audio encoder is further configured to determine a zero crossing rate of portions of the input audio information, and to identify portions of the input audio information also in dependence on whether the determined zero crossing rate is larger than or equal to a fixed or variable zero crossing rate threshold value or in dependence on whether the zero crossing rate comprises a temporal change which exceeds a zero crossing rate change threshold value.

9. The audio encoder according to claim 2 , wherein the audio encoder is configured to apply a hysteresis for identifying signal portions of the input audio information, to reduce a number of transitions between identified signal portions and not-identified signal portions.

10. The audio encoder according to claim 1 , wherein the audio encoder is configured to selectively include parameters representing a spectral envelope of a high frequency portion of the input audio information into the encoded audio information in a signal-adaptive manner as the bandwidth extension information.

11. The audio encoder according to claim 1 , wherein the low frequency encoder is configured to encode a low frequency portion of the input audio information, comprising frequencies up to a maximum frequency which lies in a range between 6 and 7 kHz, and
wherein the audio encoder is configured to selectively include into the encoded audio representation between three and five parameters describing intensities of high frequency signal portions comprising bandwidths between 300 Hz and 500 Hz.

12. The audio encoder according to claim 11 , wherein the audio encoder is configured to selectively include into the encoded audio representation 4 scalar quantized parameters describing intensities of four high frequency signal portions, the high frequency signal portions covering frequency ranges above the low frequency portion.

13. The audio encoder according to claim 11 , wherein the audio encoder is configured to selectively include into the encoded audio representation a plurality of parameters describing a relationship between energies or intensities of spectrally adjacent frequency portions, wherein one of the parameters describes a ratio or difference between an energy or intensity of a first bandwidth extension high frequency portion and a low frequency portion, and wherein other of the parameters describe ratios or differences between energies or intensities of other bandwidth extension high frequency portions.

14. An audio decoder for providing a decoded audio information on the basis of an encoded audio information, the audio decoder comprising:
a low frequency decoder configured to decode an encoded representation of a low frequency portion to acquire a decoded representation of the low frequency portion; and
a bandwidth extension configured to acquire a bandwidth extension signal using a blind bandwidth extension for portions of an audio content for which no bandwidth extension parameters are included in the encoded audio information, and to acquire the bandwidth extension signal using a parameter-guided bandwidth extension for portions of the audio content for which bandwidth extension parameters are included in the encoded audio information;
wherein the audio decoder is c

Assignees

• Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung E V

Inventors

• Disch Sascha
• Helmrich Christian
• Hilpert Johannes
• Robilliard Julien
• Schmidt Konstantin
• Wilde Stephan

Classifications

• G10L21/038

  using band spreading techniques · CPC title

• G10L19/24 Primary

  Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding · CPC title

• G10L19/26

  Pre-filtering or post-filtering · CPC title

• G10L19/265

  Pre-filtering, e.g. high frequency emphasis prior to encoding · CPC title

• G10L19/20 Primary

  using sound class specific coding, hybrid encoders or object based coding · CPC title