Bank C-A: Input Loss Mode
The
Input Loss Mode
function selects what type of video appears at the system’s four outputs when
the input signal is lost or invalid. These choices are available:
•
Black
- SDI black.
•
No Output
- flat line, no signal present.
•
Freeze
- the last valid image is automatically frozen (
ADC-8032A-S
only). The
freeze will affect either field 1, field 2 or the entire frame (as determined by the
Freeze Mode
function).
•
Re-initialize
– the card will re-initialize itself every 1.5 seconds. (This option may
be removed on future revisions.)
When a valid input signal is restored, the
Input Loss Mode
setting is ignored. Use the following steps
to set the Input Loss Mode:
1. Select Bank C, and rotate
Function Select
to position A.
2. Select the desired mode according to the table below:
•
Toggle
Mode Select
up
to advance up the list.
•
Toggle
Mode Select
down
to descend down the list.
Bank SW1 Function Select SW2 Mode Select Heads-Up Display Label Default
C
A
+ Freeze
No Output
- Black
IN LOSS RE-INIT
FREEZE
NO OUTPUT
BLACK
BLACK
Important
It is recommended that the
Hotswitch Mode
and
Input Loss
Mode
be set the same with either: both set to freeze, or both set to black.
There is circuitry in the sync stripper that removes unwanted
impulses to make the circuit more noise tolerant. During a
hotswitch, this could cause the
ADC-8032A
to interpret the signal
has been lost. Since the Input Loss mode overrides the Hotswitch
mode setting, having one set to freeze and the other set to black
could lead to a momentary glitch on the screen.
Bank C-B: Hotswitch Mode
The
ADC-8032A
uses a phase-locked-loop (PLL) to synchronize its pixel clock to the incoming
signal’s line rate. Because of this, any disturbance to the incoming line rate, such as an untimed
switch outside the lock window of the PLL, will cause the PLL to lose lock. It can take several fields
before the PLL can regain lock, and until it does so, the decoder cannot properly decode the incoming
video. The result is that untimed switches will result in a disruption to the output video.
To mask this disruption, a hotswitch mode was created. This is accomplished by momentarily freezing
the last good frame, or momentarily going to black while the untimed switch occurs. Going to black is
recommended since the output can be forced to black as soon as the hotswitch condition is detected.
Freezing must wait until the next field, in which case a single corrupted field could get through to the
output.
In Frame Sync, the output timing will be undisturbed as it is based on the external reference. In Line
Sync mode, as long as the input sources are on the same line relative to the external reference, and
they do not cross the threshold point (see Bank C-1 Timing Mode for details on the threshold point),
4-20
•
Using Banks
ADC-8032A User Manual (Iss. 04)