Miranda NV5100MC Master Control, Справочное руководство

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NV5100MC Master Control • Reference Man ual 169
A. Special Features
Machine Control and Pre-Roll
bution of any device internal latency. That is because pre-roll sources that are not also machine
control sources are not controlled by the DC21 which is the only place latency values are used.
A transition’s pre-roll time might be further modified by the system pre-roll value specified in the
general settings of MasterConfig. For any transition, the maximum of system preroll or effective
preroll will be used as that transition’s pre-roll.
We recommend that configurers set a value for system preroll at the maximum of all pre-roll values
so that all transitions will exhibit the same (maximum) preroll period.
This diagram shows a sample pre-roll transition:
Figure A-2. Pre-Roll Timing
It shows 3 pre-roll sources, A, B, and C with different pre-roll values. The pre-roll value for C — an
Intuition XG key — is small in comparison to the transition period which is 60 frames. The transi-
tion is a V-fade, so the point at which all new video must begin is 30 frames into the transition (the
middle).
The longest effective pre-roll is 162 frames. The pre-rolls and the transition are timed so that the
transition starts 30 frames before all three pre-rolls finish (simultaneously). There is therefore a
132-frame delay before the transition itself actually begins.
S
The operator is obligated to press the transition button about 4.5 seconds (132 frames) before
the program video starts to fade. Automation must also start pre-roll transitions ahead of time.
To do so, the automation system must either be able to calculate the effective pre-roll for a tran-
sition or assume a fixed (maximum) pre-roll time. A fixed system-wide preroll value can elimi-
nate the need for these calculations.
The system pre-roll value (120 frames) is not greater than the longest source pre-roll, so it is dis-
missed in this case. Had it been greater, it would have been used as the transition’s pre-roll value.
Notes
1 A source’s effective pre-roll period elapses at the first appearance of that sources video for that
transition, and typically not at the start of the transition. See Figure A-2.
2 Hot cuts can pre-roll too.
3 Master control’s machine control and pre-roll functions do little to ensure that a tape, or any
other medium, is properly cued. Correct playout is always the operator’s responsibility.
4 There is an ‘Abort’ button to cancel pre-roll transitions before a transition completes the pre-
roll period.
60
30 60 90 120 150 180
A
B
C Pre-roll = 5 sec; latency = 12 frames
Pre-roll = 3 sec; latency = 8 frames
Pre-roll = 5 frames (for Intuition XG)
Press of
Transition
Button
Pre-Roll Period
System pre-roll = 4 sec
Start A Start B Start C
Program
Preset