Abstract: A DCT coefficient output from a DCT circuit 21 is quantized by different quantization outputs by quantization circuits 22 to 25, and code lengths obtained by encoding the respective quantization outputs are calculated by code length calculation circuits 28 to 31. The code lengths corresponding to one frame obtained by the code length calculation circuits 28 to 31 are accumulated by adders 33 to 36, thereby obtaining a plurality of calculated total bit counts corresponding to the plurality of quantization coefficients. A comparator 37, multipliers 38 and 39, and an adder 40 select, of the plurality of calculated total bit counts, two calculated total bit counts that are close to a target total bit count, and obtain a scale factor used for obtaining a quantization coefficient corresponding to the target total bit count. An optimum quantization coefficient for the subsequent second scanning operation is generated by a quantization coefficient generator 27 by using the scale factor.