scope:

Introduction

Close synchronisation of signal sources and of signal processing is required in a television studio of any kind and this is particularly true in true digital studio or in studios operating in a mixed analogue and digital manner. Synchronisation is required at various levels: for the sample clock (13.5 MHz in the case of Recommendation 601), and the scanning line, field and frame, to a high degree of accuracy and stability so as to allow the freedom of mixing, effects and processing demanded in television programme production. Synchronisation is thus a basic function and its accuracy and stability are fundamental to successful television broadcasting.

Two requirements for synchronisation can be identified:-

(a) Input Synchronisation the synchronisation of the internal clocking of a process with the input signal. This is generally achieved by locking the clock generator to the input signal directly through a phase-locked leap, thus minimising jitter and drift.

(b) output Synchronisation the synchronisation of two or more signals with each other, by locking their respective generators to a common reference signal, as is generally done with cameras and telecines.