TABLE OF CONTENTS Channel status data (represented by the C bit in each subframe) is commonly a problematic area with implementations of the standard two-channel interface. It is here that a number of incompatibilities arise between devices and it is here that the main differences exist between professional and consumer formats, because the usage of channel status in consumer and professional equipment is almost entirely different. In this section the principles of channel status usage will be explained, together with an introduction to potential problem areas, although discussion of practical situations is largely reserved until Chapter 7.
Although there is only one channel status (C) bit in each subframe, these are aggregated over a period of time to form a large data word that contains information about the audio signal being transmitted. The two audio channels theoretically have independent channel status data, although commonly the information is identical, since most applications are for stereo audio. Starting with the frame containing the Z preamble, channel status bits are collected for 192 frames (called a channel status block), resulting in 192 channel status bits for each channel. This long word is subdivided into 24 bytes, each bit of which has a designated function, but the function of these bits depends on whether the application is consumer or professional. The channel status information is updated at block rate, which is 4 ms at a sampling rate of 48 kHz and longer pro rata at other sampling...
