| 摘要 |
In a fixed bit-rate encoding method, a unit block composed of a predetermined number of transform blocks is constructed by dividing input image data into transform blocks and a unit for fixing the bit-amount is constructed by extracting one of the predetermined number of unit blocks, to thereby perform transform-encoding. A real compression scale factor is calculated by quantizing the transform coefficient obtained by a transform-encoding operation according to initial compression scale factors and by comparing the bit-amount quantized in a unit block with a target bit-amount. The transform coefficient is quantized in a unit block using said real compression scale factor, and the quantized transform coefficient is variable-length-encoded to have the bit-amount fixed in an bit-amount fixing unit. The encoded DC coefficient and a predetermined number of low-frequency AC coefficients are recorded in an IDC data region and the all of the encoded coefficients are recorded in a DDC data region. The fixed bit-rate is easily performed by setting a bit-amount fixing unit as a cluster which is smaller than a frame. When the high-speed search operation is performed, information of the scanning position corresponding to each searching speed is scanned after scanning only the IDC region located in the leading end of the recording track, including most of the image information. Accordingly, most of the image information is reproduced even when the head does not scan the whole recording track.
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