US 6,708,145 B1 · Enhancing perceptual performance of sbr and related hfr coding methods by adaptive noise-floor addition and noise substitution limiting

Abstract

Methods and an apparatus for enhancement of source coding systems utilizing high frequency reconstruction (HFR) are introduced. The problem of insufficient noise contents is addressed in a reconstructed highband, by using Adaptive Noise-floor Addition. New methods are also introduced for enhanced performance by means of limiting unwanted noise, interpolation and smoothing of envelope adjustment amplification factors. The methods and apparatus used are applicable to both speech coding and natural audio coding systems.

Claims17

Dependent claims

A method for enhancing a source encoding method, the source encoding method generating an encoded signal by encoding an original signal, the original signal having a low band portion and a high band portion, the encoded signal including the low band portion of the original signal and not including the high band portion of the original signal, comprising the following steps:

estimating a noise-floor level of the high band portion of the original signal, the noise floor level being a measure for a difference between a first spectral envelope determined by local minimum points of a spectral representation of the original signal and a second spectral envelope determined by local maximum points of a spectral representation of the original signal;
and
multiplexing the encoded signal including the low band portion of the original signal and the noise-floor level of the high band portion of the original signal to obtain an encoder output signal.

An apparatus for enhancing a source decoder, the source decoder generating a decoded signal by decoding an encoded signal obtained by source encoding of an original signal, the original signal having a low band portion and a high band portion, the encoded signal including the low band portion of the original signal and not including the high band portion of the original signal, wherein the decoded signal is used for high-frequency reconstruction to obtain a high-frequency reconstructed signal including a reconstructed high band portion of the original signal, comprising:

a demultiplexer for demultiplexing an input signal including the encoded signal and a noise-floor level of the high band portion of the original signal, the noise floor level being a measure for a difference between a first spectral envelope determined by local minimum points of a spectral representation of the original signal and a second spectral envelope determined by local maximum points of a spectral representation of the original signal;
means for obtaining a spectral envelope representation of the high band portion of the original signal;
a shaper for shaping a spectrum of a random noise signal in accordance to the spectral envelope representation of the high band portion of the original signal to obtain a spectrally shaped random noise signal;
an adjuster for adjusting the spectrally shaped random noise signal in accordance to the noise-floor level to obtain an adjusted spectrally shaped random noise signal;
and
an adder for adding the adjusted spectrally shaped random noise signal to the high-frequency reconstructed signal to obtain an enhanced high-frequency reconstructed signal.

3 more elements

A method for enhancing a source decoding method, the source decoding method generating a decoded signal by decoding an encoded signal obtained by source encoding of an original signal, the original signal having a low band portion and a high band portion, the encoded signal including the low band portion of the original signal and not including the high band portion of the original signal, wherein the decoded signal is used for high-frequency reconstruction to obtain a high-frequency reconstructed signal including a reconstructed high band portion of the original signal, comprising the following steps:

demultiplexing an input signal including the encoded signal and a noise-floor level of the high band portion of the original signal, the noise floor level being a measure for a difference between a first spectral envelope determined by local minimum points of a spectral representation of the original signal and a second spectral envelope determined by local maximum points of a spectral representation of the original signal;
obtaining a spectral envelope representation of the high band portion of the original signal;
shaping a spectrum of a random noise signal in accordance to the spectral envelope representation of the high band portion of the original signal to obtain a spectrally shaped random noise signal;
adjusting the spectrally shaped random noise signal in accordance to the noise-floor level to obtain an adjusted spectrally shaped random noise signal;
and
adding the adjusted spectrally shaped random noise signal to the high-frequency reconstructed signal to obtain an enhanced high-frequency reconstructed signal.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application

09/647,057Filed 20 Dec 2000

Priority

SE 990025627 Jan 1999

Granted

16 Mar 2004

Term ends

Not estimatedThe source records don’t support an estimate.

Classification8 codes

G10L 19/028
Using spectral analysis, e.g. transform vocoders or subband vocoders: noise substitution, i.e. substituting non-tonal spectral components by noisy…
G10L 19/06
Using predictive techniques: determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
G10L 19/26
Using predictive techniques: pre-filtering or post-filtering
G10L 19/265
Pre-filtering or post-filtering: pre-filtering, e.g. high frequency emphasis prior to encoding

Abstract

Facts

Application

09/647,057Filed 20 Dec 2000

Priority

SE 990025627 Jan 1999

Granted

16 Mar 2004

Term ends

Not estimatedThe source records don’t support an estimate.

Classification8 codes

G10L 19/028
Using spectral analysis, e.g. transform vocoders or subband vocoders: noise substitution, i.e. substituting non-tonal spectral components by noisy…
G10L 19/06
Using predictive techniques: determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
G10L 19/26
Using predictive techniques: pre-filtering or post-filtering
G10L 19/265
Pre-filtering or post-filtering: pre-filtering, e.g. high frequency emphasis prior to encoding

Enhancing perceptual performance of sbr and related hfr coding methods by adaptive noise-floor addition and noise substitution limiting

Life of this patent

Abstract

Claims17

Enhancing perceptual performance of sbr and related hfr coding methods by adaptive noise-floor addition and noise substitution limiting

Life of this patent

Abstract

Claims17