Method for computing nonlinear function in inverse quantization formula

A technology of nonlinear functions and formulas, which is applied in the field of audio compression algorithms and can solve problems such as high computational overhead

Inactive Publication Date: 2006-03-01
GUANGDONG VIMICRO
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Problems solved by technology

[0021] If f: [a, b] → R is a continuous function defined in the closed interval [a, b], ε > 0, then there is a polynomial function P ε (x), such th...

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  • Method for computing nonlinear function in inverse quantization formula

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Embodiment Construction

[0050] It can be known from formula (2) that two nonlinear functions are involved in the AAC dequantization formula, one is |X quant (k)| 4 / 3 , where |X quant |The range is 0~8191; the other is 2 1 / 4·(globalg ain-scf) . 2 of them 1 / 4*x The calculation of the function is relatively simple, and the following method can be used for calculation:

[0051] Y=2 1 / 4*x

[0052] Using the strategy of floating-point quantization, the result of Y is expressed in two parts: the mantissa part Y fract (|Yfract |≤1, expressed as a binary fraction) and the exponent part Y of 2 exp (in binary integer representation), then

[0053] Y = Y fract * 2 Y exp = ( Y fract ) Y exp

[0054] Usually we only need to add 2 0 / 4...

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Abstract

A method for calculating nonlinear function in counter quantization formula includes counting distribution probability of quantized spectral coefficient in code stream , calculating nonlinear function with table looking - up method in scope that occurrence probability of quantized spectral coefficient is relatively concentrated , using polynomial approximation to calculate nonlinear function is scope that occurrence probability of spectral coefficient is not relatively concentrated.

Description

technical field [0001] The invention relates to the field of audio compression algorithms, in particular to a method for calculating nonlinear functions in inverse quantization formulas. technical background [0002] AAC (Advanced Audio Coding) is a new audio compression algorithm formulated by the ISO MPEG organization in the MPEG-2 compression standard, which was further enhanced in the MPEG-4 standard later. AAC and MP3 algorithm are not compatible with each other. Compared with MP3 algorithm, AAC adopts some new encoding tools. Therefore, under the same compression quality, AAC has a higher compression ratio than MP3. When an AAC decoder is implemented on a hardware device, usually the device only supports fixed-point operations and does not support floating-point operations due to power consumption and cost reasons. figure 1 The structure diagram of the AAC decoder is given. When the decoder is implemented on a fixed-point device, since the inverse quantization formula...

Claims

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Application Information

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IPC IPC(8): H03M7/30G10L19/00
Inventor 冯宇红邓昊
Owner GUANGDONG VIMICRO
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