What interfaces are used for digital audio transmission?
S / PDIF (Sony / Phillips Digital Interface Format – digital information format
terface from Sony and Philiрs) – digital interface for home radio
team.
AES / EBU (Society of Audio Engineers / European Broadcasting Union – Society
sound engineers / European Broadcasting Association) – digital engineering
terface for studio radio equipment.
Both interfaces are serial and use the same form
marking mat and coding system: BMC code with automatic synchronization
(Biphasic brand code: code with a double change representation of a unit
phase) and can transmit signals in PCM format of up to 24 bits
at sample rates up to 48 kHz.
Each signal sample is transmitted as a 32-bit word (frame), in which
rum 20 digits are used to transmit the count, and 12 – to form
synchronization preamble, transmission of additional information and
parity bit. 4 bits of the service group can be used to
extension of the sample format to 24 bits.
192 consecutive frames form a block, the beginning of which is marked
special preamble code of the first frame.
In addition to the parity bit, the service part of the word contains a validity bit
(Validity), which must be zero for each valid answer
accounts. If a word is received with a single bit of Validity or with a violation
parity in the word, the receiver interprets the entire sample as wrong and
you can choose to replace it with the old value or interpolate
based on multiple adjacent valid reads. Counts
marked invalid can transmit CD players that
DAT recorders and other devices, yes, when reading information from
the media could not be corrected during read errors
Ki.
The service part of the word also includes the C bits (Channel Status – Status
channel) and U (user bit). Constant price
kidney of each of these bits, taken one at a time from each block frame,
forms a 192-bit word of block service bits, where information is transmitted
information about the title of the work, track number,
device, CD subcodes, etc. S / PDIF transmits
copy protection settings (SCMS).
The standard encoding format is designed to transmit one and two
channel signal, however, when service bits are used to
By encoding the channel number, a multi-channel signal can be transmitted.
On the electrical side, S / PDIF provides a coaxial connection
cable with characteristic impedance of 75 ohms and RCA connectors (“tulle
pan “), signal amplitude – 0.5 V. AES / EBU provides connection
2-wire shielded symmetrical cable with transformer
decoupling via RS-422 interface with signal amplitude 3-10 V, connectors –
Cannon XLR 3-pin. There are also optical options
transceivers: TosLink (plastic fiber) and AT&T Link
(fiberglass).
