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Method for post-processing a signal in an audio decoder

An audio decoder and decoder technology, applied in the direction of instruments, speech analysis, etc., can solve problems such as difficult to apply models

Inactive Publication Date: 2009-04-08
FRANCE TELECOM SA
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Problems solved by technology

However, without coupling between excitation and shaping, such a model is difficult to apply and leads to typical artifacts in the form of very easily audible local "clicks" due to severe exceeding of the above amplitude limits

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  • Method for post-processing a signal in an audio decoder
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  • Method for post-processing a signal in an audio decoder

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Embodiment Construction

[0042] It should be remembered that the general context of the invention is sub-band hierarchical audio encoding and decoding at three bit rates (8kbps, 12kbps and 13.65kbps). In practice, the encoder always operates at a maximum bit rate of 13.65kbps, and the decoder can receive a core of 8kbps, and either or both enhancement layers of 12kbps or 13.65kbps.

[0043] Figure 2 is a diagram of a hierarchical audio encoder.

[0044] First, the broadband input signal sampled at 16 kHz is divided into two sub-bands by filtering it using QMF (Quadrature Mirror Filter Bank) technique. The first frequency band (low band) in the range of 0 to 4000 Hz is obtained by low-pass (L) filtering 400 and decimation (decimation) 401, and the second frequency band in the range of 4000 Hz to 8000 Hz is obtained by high-pass (H) filtering 402 and decimation 403 Second band (high band). In a preferred embodiment, the L and H filter lengths are 64 and are in accordance with the paper "A filter famil...

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Abstract

The invention relates to a method for post-processing, in an audio decoder, a signal reconstructed by the temporal and frequential shaping (805, 807) of an excitation signal obtained on the basis of at least one parameter in a first frequency band, said temporal and frequential shaping being carried out at least on the basis of a temporal envelope and a frequential envelope received and decoded (801, 802) in a second frequency band. The method is such that, once the shaping (805,807) has been carried out, steps of comparing the amplitude of the reconstructed signal with the received and decoded temporal envelope (s) are followed, and an amplitude compression is applied to the reconstructed signal if at least one threshold of the temporal envelope is exceeded. The invention relates to a post-processing module for implementing the inventive method, and to an audio decoder. It is used for transmitting and storing digital signals such as audiofrequency signals: speech, music, etc.

Description

technical field [0001] The invention relates to a method for post-processing a signal in an audio decoder. [0002] The invention finds a particularly beneficial application for the transmission and storage of digital signals such as audio signals (speech, music, etc.). Background technique [0003] Various techniques exist for digitizing and compressing audio speech, music, etc. signals. The most common methods are "waveform coding" methods such as PCM and ADPCM coding, "parametric analysis by synthesis coding" methods such as code excited linear prediction (CELP: code excited linear prediction) coding, and "subband coding" methods. Or transform perceptual coding (sub-band or transform perceptual coding)" method. [0004] These are described, for example, in "Vector Quantization and Signal Compression", A. Gersho and R.M. Gray, Kluwer Academic Publisher, 1992, and "Speech Coding and Synthesis", B. Kleijn and K.K. Paliwal, Editors, Elsevier, 1995. Classic technique for en...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G10L21/02G10L19/04G10L19/14G10L19/24
CPCG10L19/04G10L21/0205G10L19/24G10L21/0364G10L19/26
Inventor 斯蒂芬·拉戈特西里尔·吉劳姆
Owner FRANCE TELECOM SA
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