Site Contents
- Introduction
- Audio Data Format
- Interface Applications
- Hardware Specifications
- Data Transmission
- Digital-Analog Converter
- Resetting & Auto-Switching
- History & Characteristics
- Data & Cabling Details
- Coding Format
- Conversion Circuits
- Internal Connection
- External Connection
- Optical Output Circuit
- Transmission Line
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SPDIF: History & Characteristics
Background
Advent of Compact Disc (CD) Player in the early 1980s was a step in the direction of digital audio. At the initial stage, the signals were within the cabinet and could leave only after conversion to analog signal. Now the mission is keeping the signals in digital domain for as long a period as possible as that is the only means to ensure rich signal quality. Communication of various devices with each other in the digital domain is required to achieve this quality.
Introduction Of SPDIF
The task as stated above gave rise to many interfaces that ultimately evolved into the global audio standard IEC958 from EBU. In Japan however the equivalent of this standard is EIAJ CP-340. Sony Philips Digital Interface Format and the hi-fi audio system SACD were developed by Sony and Philips jointly. The latter has found a rival in DVD-audio both competing in the war of format. Public preference is however still tilted towards CDs because of their widespread presence in consumer devices.
Characteristics
SPDIF or the standard digital audio interface IEC958 of EBU (European Broadcasting Union) has specified characteristics. The audio format is linear 16 bit by default but can be expanded up to 24 bit. Audio sampling frequencies permitted are 44.1 kHz from CD, 48 kHz from DAT and 32 kHz from DSR. Communication is one way from transmitter to receiver. Control information bit is VUCP (Validity, User, Channel Status, and Parity). The bit V indicates validity of the audio sample. Bit U is user free coding for song runtime and track number. Sampling rate, copy permit and emphasis are represented by bit C. P bit is for detecting error to ensure quality reception. Coding format is Bi-phase mark except the preambles for the purpose of sync. Bandwidth occupation is from 100kHz to 6Mhz but without DC. Signal bit rate according to the sample frequencies are 2.8Mhz, 2Mhz and 3.1Mhz for 44.1kHz, 32kHz and 48kHz respectively.