Crystal Vision
Introduction
TANDEM-200 User Manual R1.7
9
13/02/2008
External reference
Digital output option cards may be used with an external word clock or AES reference.
Link jumpers are provided on the digital option cards to select 110 Ohm, HiZ or 75 Ohm
impedance.
Handling ancillary data
Ancillary data can be placed in both the vertical and horizontal blanking intervals of the
serial component video signal (SDI). The vertical ancillary data space or VANC is used
for such data as VITS or VITC whilst AES/EBU digital audio data is embedded in the
horizontal blanking data interval or HANC. Data packet management provides controls to
choose how new audio packets created for re-embedding audio are inserted into the
HANC data space.
Data packet management provides the following ancillary data handling options:
•
Support for contiguous HANC data packing
•
Automatic mark audio group for deletion
•
Blank entire HANC data space, except the EDH insert
•
Wide range of formats to embed on all HANC lines or leave a gap around the
vertical switching point
•
Variable error masking and error handling
•
Enable or disable EDH processing
Details of HANC processing and EDH processing can be found in the Data Packet
Management chapter.
SDI PLL function
There is a single PLL module, like a "time base corrector" that may be inserted into either
SDI 1 only, SDI 2 only, or left out of circuit (OFF).
The SDI signal accumulates an ever-increasing amount of jitter as it progresses through
an SDI installation, and as it passes through most equipment in its path. To minimise this
effect, TANDEM-100 has an SDI crystal controlled re-clocker which sets the output SDI
signal to the same mean frequency as the input, but re-clocked by a crystal controlled
Phase Locked Loop [PLL]. This produces extremely low jitter in the SDI output, even in
the presence of a very high level of jitter in the incoming signal. Typically, jitter of 1 or 2
nanoseconds peak to peak will be reduced to a few hundred picoseconds.
The PLL can be placed in either an SDI 1 or SDI 2 input path prior to processing, so all of
the functions of that side, as well as the SDI output, benefit.
