Patent ID: 7672522

Claim:
An image decoding apparatus for performing a decoding process under a prescribed coding method, comprising: a decoding unit configured to perform the decoding process on picture data encoded with the coding method; and a control unit configured to control the decoding unit based on types of a mode signal received by the control unit such that the decoding unit: performs a first process as part of the decoding process to extract and decode an I-picture and prescribed pieces of P-pictures based on a location of the I-picture in the picture data when the received mode signal is of a first type; performs a second process as part of the decoding process to decode a macroblock in the picture data based on a prediction signal obtained through reversible encoding when the received mode signal is of a second type; and performs a third process to decode as part of the decoding process direct current components of transformation coefficients with transformation coding when the received mode signal is of a third type.