Frame identification system

摘要

A digital television signal includes successive frames of two fields each comprising 313 data segments with the first data segment in each field functioning as a field sync. The field sync segment comprises a 511 PN sequence and three 63 pseudo-random number (PN) sequences, with the middle one of the 63 PN sequences alternating polarity in successive fields. A reference data segment is compared with the 511 PN sequence in each data segment and the data segment with the least number of errors is identified as the first data segment in the field. The corresponding portion of the reference segment is compared with the middle 63 PN sequences in the identified first data segments and that with the least number of errors is determined to be the first segment in the frame. Confidence counters are used to assure reliable determinations.