Abstract: An encoder, a method for adjusting decoding calculation, and computer program product therefor are provided. The encoder, comprising a parameter generator, an adder and a complexity computation unit, adjusts decoding calculation according to a first encoding parameter which is generated based on a video frame. The method and the computer program product therefor operate: the parameter generator to generate an image quality parameter; the adder to add the first encoding parameter and the image quality parameter to generate a second encoding parameter; the complexity computation unit to perform a complexity computation according to the second encoding parameter and to generate a third encoding parameter and an updating parameter; the parameter generator to update the image quality parameter according to the updating parameter; and the encoder to encode the video frame based on the third encoding parameter.