A detecting circuit detects a boundary in a bit stream which is coded in compliance with a predetermined rule. The boundary is a point at which discontinuity of reproduction time occurs. An inverting circuit inverts a specific bit in a header of a succeeding bit stream immediately subsequent to the boundary, in response to the detection of the boundary by the detecting circuit. The boundary can thus be detected easily by simply monitoring the specific bit, for example, in outputting the decoded bit streams. This consequently facilitates synchronous management and the like of the bit streams. The specific bit is included in the bit stream. Thus, detecting the specific bit allows simple and accurate detection of the boundary at which discontinuity of the reproduction time occurs.