Patent ID: 6829576
Filing Date: 2004-12-07
Classification: G10L

Abstract:
A nonlinear operation method suitable for audio encoding, existing in a quantization process for audio encoding, the nonlinear operation equation is Æ’(X) =X3/4, wherein X represents a frequency-field data, and the nonlinear operation method suitable for audio encoding comprising:building up a query table, the query table comprising a plurality of frequency-field data X and a plurality of corresponding values f(X) that correspond to the frequency-field data X, wherein the query table is represented as a function T(X), and T(X)=X3/4, 1&lE;X&lE;S, where S represents a data range included in the query table; analyzing and providing a modified error quantity function fa(z) represented by a power of 2 equation, wherein let z=&LeftFloor;X16n&RightFloor;,â€ƒn=1, 2 or 3 to have z fall in the data range S of the query table; wherein when the frequency-field data X that is intended to query is greater than the data range S, the values of T(z) and T(z+1) are obtained from the query table and are defined as Y1 and Y2, respectively, where z and (z+1) fall in the data range S of the query table, respectively; and calculating a corresponding value f(X) of any one of the frequency-field data X that is beyond the data range S by using a two-phase interpolation method, comprising the steps of: multiplying Y1 and Y2 by a recover coefficient respectively to obtain a corresponding value of X1 and X2, i.e. f(X1) and f(X2), respectively; generating a secant equation that passes through two points of f(X1) and f(X3); eliminating a maximum error quantity in a [X1, X2] interval via the modified error quantity function fa(z) according to the secant equation, so as to divide a range from f(X1) to f(X2) into two segments, and to obtain a value of f(X3) that has a minimum error; obtaining a corresponding value f(X) of any one of the frequency-field data X in an [X1, X3] interval via the interpolation method; and obtaining a corresponding value f(X) of any one of the frequency-field data X in an [X3, X2] interval via the interpolation method.