The ISDB-T multiplex frame pattern explained

ISDB-T defines the so-called Broadcast Transport Stream, an MPEG transport stream adapted to carry hierarchical information. This BTS is created in the transmission side, but it has to be perfectly recovered in reception. To that end there is an algorithm defined in the standard which we found not clear regarding the implementation. We also found the bibliography regarding this algorithm was poor. After our experience implementing gr-isdbt, the first open, free and software-based ISDB-T receiver, fully implemented in GNU Radio, we were able to understand this algorithm and decided to describe it step by step from the implementation point of view.