| 摘要 |
In a MPEG audio decoding process, an IDCT (Inverse Discrete Cosine Transform) process that generates time domain samples from frequency domain samples using a very limited number of prestored cosine coefficients is performed. Only the cosine coefficients that satisfy cos(pi*(i/64)) where i=0-32 are prestored. The cosine coefficients for i=33-63 are calculated using the prestored coefficients by changing a sign of a corresponding symmetrical one of the stored coefficients, respectively. Then, sixty-four time domain samples (Vi) are generated from thirty-two frequency domain samples (Sk) according to the equation <math-cwu id="MATH-US-00001"> <number>1</number> <math> <mrow> <msub> <mi>V</mi> <mi>i</mi> </msub> <mo>=</mo> <mrow> <munderover> <mo>∑</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mn>31</mn> </munderover> <mo>it</mo> <mrow> <mrow> <mi>cos</mi> <mo>⁡</mo> <mrow> <mo>(</mo> <mrow> <mrow> <mo>(</mo> <mrow> <mi>pi</mi> <mo>/</mo> <mn>64</mn> </mrow> <mo>)</mo> </mrow> <mo>it</mo> <mrow> <mo>(</mo> <mrow> <mi>i</mi> <mo>+</mo> <mn>16</mn> </mrow> <mo>)</mo> </mrow> <mo>it</mo> <mrow> <mo>(</mo> <mrow> <mrow> <mn>2</mn> <mo>it</mo> <mi>k</mi> </mrow> <mo>+</mo> <mn>1</mn> </mrow> <mo>)</mo> </mrow> </mrow> <mo>)</mo> </mrow> </mrow> <mo>x</mo> <msub> <mi>S</mi> <mi>k</mi> </msub> </mrow> </mrow> </mrow> </math> <mathematica-file id="MATHEMATICA-00001" file="US20020173967A1-20021121-M00001.NB"/> <image id="EMI-M00001" wi="216.027" he="24.97635" file="US20020173967A1-20021121-M00001.TIF" imf="TIFF" ti="MF"/> </math-cwu> where i=0 to 63, using only the prestored cosine coefficients and the calculated cosine coefficients.
|
