| 摘要 |
In a quantizing circuit 15 , DCT coefficients output from a DCT circuit 14 are quantized with the quantizing step corresponding to a quantizing index supplied from a quantizing index determining circuit 25 . In the quantizing index determining circuit 25 , the quantizing index is determined on the basis of a first variable corresponding to an occurrence code amount as a data accumulative amount of a buffer 17 and a second variable corresponding to the activity of macroblocks output from an activity detection circuit 24 . In this case, the quantizing index determining circuit 25 adaptively sets a fixing mode for fixing the first variable or a variable mode for making variable the first variable.
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