JP2872774B

A method and an apparatus for decoding image signals capable of achieving a reproduction of the image signals with a high image quality by using a relatively low speed inverse orthogonal transform device. In the apparatus, interframe difference information is integrated by using the orthogonal transform coefficients for the interframe differential signals recovered from the input encoded signals in order to reproduce the image signals, which is carried out in one of two processing modes including: a first processing mode for applying an inverse orthogonal transform to the orthogonal transform coefficients in order to recover the interframe differential signals, and then integrating the interframe difference information by using the recovered interframe differential signals on a pel domain defined in terms of picture elements, in a case where a number of input blocks per unit time in the input encoded signals is less than a prescribed threshold value; and a second processing mode for integrating the interframe difference information by using the orthogonal transform coefficients on a transformed domain defined in terms of the orthogonal transform coefficients, in a case where the number of input blocks per unit time in the input encoded signals is not less than a prescribed threshold value.