VISTEK V1667, V1667/SY & V1667/SY-VHS
12-bit pal/ntsc to sdi adaptive
comb filter decoder
6
Issue 3
2.2
Frame Synchroniser Module (Optional)
A Frame Synchroniser module may be optionally fitted to the V1667. It is located into sockets P1, P2, P3 and
P4. Its presence is automatically detected by the on board micro-processor and is consequently integrated
into the signal processing path.
With a Frame Synchroniser fitted, the user may adjust the V1667 output timing relative to the reference input
by up to a maximum offset of + 127 lines. This operation is described in Section
5.2 Timing Parameter
Selection and Adjustment
.
If a Frame Synchroniser module is fitted, but there is no reference input, then the decoder will enter a
minimum delay mode. In this mode the synchroniser is bypassed, and the delay through the unit is fixed at
7µs.
See Section
8.3 VHS Input Option
for a description of the VHS frame synchroniser option.
2.3
Frame Synchroniser Delay
When the Frame Synchroniser option is fitted there is a TTL output signal to indicate the amount of extra
delay inserted above the minimum as specified for the unit. The signal has a constant period of two frames
and a variable mark space ratio which depends on the amount of delay inserted. The HIGH portion of the
signal indicates the delay.
A typical waveform is as shown below:
DELAY
2 FRAMES
Note:
If the input and reference signals are asynchronous then the width of the delay pulse will vary,
and will be dependent on the relative timing of the two signals.
2.4
Insertion Delay
The insertion delay through the V1667 is dependent on whether a Frame Synchroniser option is fitted.
Without a Frame Synchroniser it is deterministic and fixed. With the Frame Synchroniser fitted there is a
delay range, and the absolute delay will be dependent on the relative timing between the input video signal
and the reference input.
In each case the delay is measured between the composite video input and the input to the SDI serialiser.
Condition
Unit Delay
V1667 + No Frame Synchroniser Module
7µs
V1667 + Frame Synchroniser Module
7µs (Minimum)
1 Frame + 7µs (Maximum)
