Enhancing Perceptual Performance of SBR and Related HFR Coding Methods by Adaptive Noise-Floor Addition and Noise Substitution Limiting
First Claim
7. 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 high 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 a high-frequency reconstruction to obtain a high-frequency reconstructed signal including a reconstructed high band portion of the original signal, comprising:
- generating a reconstructed high band from the decoded signal;
adaptively adding noise to the reconstructed high band, wherein such a noise level is added that a high-frequency reconstructed signal having a noise content similar to the noise content of the original signal is obtained.
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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.
38 Citations
10 Claims
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7. 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 high 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 a high-frequency reconstruction to obtain a high-frequency reconstructed signal including a reconstructed high band portion of the original signal, comprising:
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generating a reconstructed high band from the decoded signal; adaptively adding noise to the reconstructed high band, wherein such a noise level is added that a high-frequency reconstructed signal having a noise content similar to the noise content of the original signal is obtained.
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8. Encoder comprising:
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an audio coder for encoding an audio signal to obtain an encoded signal, the encoded signal including the low band portion of the original signal and not including the high band portion of the original signal, comprising; a noise estimation device for estimating a level of noise to be added in a high-frequency regeneration process at a decoder; and an envelope extraction unit for extracting a spectral envelope of the original signal to be used for adjusting a reconstructed high-band portion of the original signal. - View Dependent Claims (1, 2, 3, 4, 5, 6, 9, 10)
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9-1. Encoder in accordance with claim 8, in which the noise estimator is operated to perform an analysis by synthesis approach for determining the noise level.
Specification