Broadcast Engineer's Reference Book
Providing detailed coverage and quick access to key technologies, standards and practices, this authoritative reference work covers the broad landscape of television technology in one handy source.
TABLE OF CONTENTS Broadcast Engineer's Reference Book
Chapter 2.6: Sound in Syncs
Gordon Anderson
Technical Training
Tandberg Television Ltd
Overview
'Sound in Syncs' (SiS) is the name for the process of placing digitally encoded sound into the line sync portion of a composite TV signal. Mono SiS (then just called SiS) was developed in the late 1960s by the BBC and was the first hybrid multiplex of analogue and digital signals in common use in broadcasting.
SiS confers all the benefits of digitising a waveform (improved signal-to-noise, low distortion, no degradation with distance) on the audio signal. In addition, SiS also 'marries' the audio and video signals together, so that they can travel through a complex contribution or distribution system without becoming inadvertently separated and without 'lip-sync' problems occurring.
The challenge for the designers of these systems was to introduce a digital signal into a complex analogue waveform without introducing crosstalk into the video ('sound on vision').
2.6.1 Mono Sound in Syncs
Mono SiS was used by broadcasters in the United Kingdom for over 15 years (from 1970 onwards) before being gradually replaced by a 'Dual-Channel' (DC) system. The digital audio was converted back to analogue before being transmitted. The use of SiS improved sound quality everywhere in the UK but the major beneficiaries were those who lived furthest from the London studios.
The EBU Eurovision network used Mono SiS from 1974 until it was superseded by an MPEG-2 digital system in 1997.
Mono SiS was also used by Bell Canada on its terrestrial circuits.
2.6.1.1 Sampling
The audio signal is passed...
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