Priori training in a mobile DTV system

An apparatus for decoding digital data includes a processor for recreating a priori training information received with the digital data for provision to a maximum a posteriori (MAP) decoder. The processor detects locations of symbols in the input data stream and regenerates data corresponding to each location. The regenerated data is used by the processor to recreate a priori information suitable to each location of the input data stream location and provides the recreated a priori information to the MAP decoder to aid in the decoding of the digital data. In a preferred implementation, the a priori training data is structured so that after deterministic processing and trellis encoding at the transmitter, it can be regenerated by the processor as a pseudo noise (PN) sequence using a PN sequence generator.