How does the HDCD Decoder detect a valid command code packet?
During the encode process by the Model 1 HDCD Processor, as one of the last steps during the formation of the command code packet, a synchronizing pattern is prepended to the data and a checksum is calculated and appended. Upon decode by the HDCD Decoder, the LSB of the audio is processed via a pattern matching circuit. If a specific synchronizing pattern is detected and it has valid format and matching checksums, only then is a command code packet registered as valid for that channel.
