digico D5T, Руководство по эксплуатации

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4-23
Chapter 4
4.8.3 External Sync Sources ........................................................
Word Clock and AES/EBU
The worksurface rear panel has connectors for Word Clock and AES/EBU inputs, either of which can be used as the master sync source
by pressing the appropriate on-screen button - note that the AES/EBU worksurface input is for sync only, and cannot be used for audio.
Video Sync
Also located on the worksurface rear panel is the Video Sync input. Although this carries only a frame boundary signal, the console can
generate a full digital word-clock from it. This means that when you choose to sync to the video signal, you have to choose the sample
rate you want to generate between frame boundaries, in just the same way as when the console is providing the master sync.
Sync to Audio Signal
Any of the console's digital audio inputs can be selected as sync source. If you choose the Audio Signal option in the Sync control panel,
you can then choose any input signal group and number, in just the same way as the audio component of the signal is selected as the
source for a console input channel. When you have selected a signal group, the panel displays a green "OK " light to indicate when a
signal in that group carries a valid sync source.
Please note the Digico's experience shows by far the most trouble free master sync source will be an AES/EBU signal (from the AES sync
input or audio input). Word clock is second best and video is the more difficult source to implement.
4.8.4 Sample Rate and Conversion .............................................
The default sample rate for the console is set up at installation, and it is this sample rate which will be used when the console is operating
as the master digital sync source. If the console is synchronised with an external digital audio unit, the sample rate used by the external
unit becomes the master sample rate for the system.
Sample Rate Convertors
The AES/EBU Rack Modules are equipped with input Sample Rate Convertors (SRC). By default these are switched on at all times.
These allow the console to synchronise incoming digital signals of differing sample-rates, to avoid the glitching which occurs when signals
with different sample-rates are mixed.
SRC also allows the same sample rate but different clock phase to be connected without problems (such as systems locked to external
video sources).
SRC is also provided on the AES/EBU outputs. By default the outputs are locked to the console rate, however other rates can be preset to
specific outputs, for example to allow a 44.1KHz output to a CDR from a console running 48KHz.
Switching of both the input and output SRC is not adjustable from the mixer screens but is configured in the socket setup file of the control
computer, as this requires careful consideration of clocking issues within the system as a whole. For most users the default setup will
work for the majority of applications.