An encoding system conversion apparatus includes an encoding parameter prediction unit, which analyzes a first encoded image data encoded by a first encoding system that is intermittently read from a recording medium, and which predicts an encoding parameter for encoding with a second encoding system that is different from the first encoding system. The system also includes a conversion unit that converts the first encoded image data read out continuously from the recording medium to a second encoded image data by the second encoding system, based on the encoding parameter predicted by the encoding parameter prediction unit.