User manual

Digital Interface Tester
4-127
AM700 Audio Measurement Set User Manual
Digital Interface Terminology
Sampling frequency Frequency of the audio signal samples. If more than
one audio signal is transmitted through the same inter-
face, the signal samples are at the same frequency.
Audio sample word Digital audio signal amplitude. Representation is linear
in a twos complement binary form. Positive numbers
correspond to positive analog voltages at the input of
the analog-to-digital converter (ADC). The number of
bits per word can be specified from 16 to 24 in two
coding ranges (less than or equal to 20 bits and less
than or equal to 24 bits).
Auxiliary sample bit The four least-significant bits (LSBs) can be assigned
as auxiliary sample bits and used to carry information
when the number of audio sample bits is less than or
equal to 20.
Validity bit A bit used to indicate if the audio sample bits in the
subframe (time slots 4 to 27 or 8 to 27, depending on
the audio word length) are suitable for analog conver-
sion.
Channel status Bits that are coded with information associated with
each audio channel. The bits are in a fixed format
derived from a block (a group of 192 consecutive
frames).
User data Bits provided to carry any other information.
Parity bit A bit used to detect an odd number of errors occurring
in the interface.
Preambles Specific bit patterns at the beginning of a subframe
used for synchronization. There are three bit patterns
and their inverse recognized as preambles in the digital
data stream.
Subframe Defined fixed data structure used to carry the digital
information.
Frame Two successive and associated subframes.