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.