| 摘要 |
An image decoder which applies a decoding process to image data includes a module for applying a variable length decoding process to a first image data, a module for applying an inverse quantizing process to the first image data, a module for determining a mode of discrete cosine transform of the first image data, and inverse discrete cosine transform module for obtaining a second image. The inverse discrete cosine transform module transforms the first image data into the second image having a lower degree than the first image data when the mode is a field mode, which performs the discrete cosine transform by each field, using a first basis. The inverse discrete cosine transform module transforms the first image data into the second image with keeping field information when the mode is a frame mode which performs the discrete cosine transform by each frame, using a second basis. A number of calculations included in the inverse discrete cosine transform using the second basis function is substantially equal to a number of calculations included in the inverse discrete cosine transform using the first basis.
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