What does the HDCD code look like?
The HDCD code is very similar to the packet type of data sent in the Ethernet network protocol. During the final quantization, the encoder inserts it into the least significant bit (LSB) of the 16 bit audio word. Specifically, these code packets are only a little more than one millisecond in duration and are inserted at several 10s of millisecond intervals. The packet of HDCD code is a pseudo random noise encoded bit stream that is only inserted when the encoder deems it necessary to inform the decoder that a change in the encoding algorithm has occurred. This pseudo random code is used for the HDCD command function less than five percent of the time (typically only 1-2 percent). The use of the 16th bit for the HDCD command code is inaudible because the code is inserted for only a very small portion of time and because it is used as dither for the remaining 15 bits when it is inserted. Pacific Microsonics experimentally confirmed this by inserting the HDCD code at several times the nor
