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Delay-optimized overlap transform, coding/decoding weighting windows

A coding and windowing technology, applied in code conversion, multi-frequency code system, speech analysis, etc., can solve the problems of not particularly strong frequency selectivity, no degree of freedom, and reduced audio quality of encoded signals

Active Publication Date: 2014-07-16
ORANGE SA (FR)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0018] However, this technique, although it enables a reduction in latency, does tend to resemble a rectangular window when the reduction in latency increases
The frequency selectivity of this window form is not particularly strong and basically degrades the audio quality of the encoded signal completely
Also, it greatly limits the window due to the inclusion of 4Mz samples in its construction
There are not many degrees of freedom available for providing an effective window for encoding, especially to provide significant frequency selectivity

Method used

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  • Delay-optimized overlap transform, coding/decoding weighting windows
  • Delay-optimized overlap transform, coding/decoding weighting windows
  • Delay-optimized overlap transform, coding/decoding weighting windows

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Embodiment Construction

[0082] Referring first to FIG. 7, a method of encoding / decoding a digital signal (given in step 70) by transform with overlap will be described as the basic framework for implementing the present invention. The method comprises a step 71 of dividing the digital audio signal into frames of length M. Each frame is then grouped with its predecessor, corresponding to a 50% overlap. In the next step 72, the analysis window h a is applied to the collection of these two frames. Fig. 6 shows an exemplary analysis window h according to the present invention a (Amplitude from 0 to 1 as a function of the number of samples "Nb Ech"). It will be noted that the analysis window h a Ends at Mz value of 0 and has a total length of 2M.

[0083] The next step 73 consists in pairing the window h a The weighted blocks of the two frames are transformed, for example of the type MDCT, and the values ​​are quantized in the transform domain (step 74). In decoding, an inverse transformation, in s...

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Abstract

The invention relates to the coding / decoding of a digital signal, consisting of successive blocks of samples, the coding being of the transform with overlap type and comprising, upon analysis, the application of a weighting window to two blocks of M successive samples. In particular, this weighting window is asymmetric and comprises four distinct portions extending successively over the two aforesaid blocks, with: a first portion (wl), increasing over a first interval of samples, a second portion (w2), constant at a value of 1 over a second interval, a third portion (w3), decreasing over a third interval, and a fourth portion (w4), constant at a value of 0 over a fourth interval.

Description

technical field [0001] The present invention relates to the field of coding / decoding of digital audio signals, and more particularly to the field of so-called "transformed audio coding / decoding with overlap". Background technique [0002] "Transform coding" consists in encoding a time domain signal in the transform (frequency) domain. This transformation enables, inter alia, the use of the frequency characteristics of the audio signal (music, speech, etc.) in order to optimize and increase the coding efficiency. For example, the fact that harmonic sound is represented in the frequency domain by a finite and small number of spectral waves can be applied, so it can be coded compactly. For example, frequency masking effects can also advantageously be applied to format coding noise in as silent a manner as possible. [0003] Standard transform coding techniques are summarized as follows. [0004] The digital audio stream to be encoded (at a given sampling frequency Fs) is div...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G10L19/02G10L19/032
CPCG10L19/0212G10L19/022H04L27/2639H03M7/02G10L19/008G10L19/02G10L19/12H03M7/00H03M7/30H03M7/46H04L27/26
Inventor 朱利恩·福雷皮埃里克·菲利普
Owner ORANGE SA (FR)