Miranda NV5100MC Master Control, Справочное руководство

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60 Rev 2.10 • 17 Feb 11
4. MCPMs
MCPM Architecture
3 An effect in “clear preset” mode is removed from the preset bus immediately after a transition
(unless it was on program before the transition).
While the MCPM is performing a transition, it does not allow changes to:
1 The preset bus.
2 The video effects on the program bus.
3 The audio overs on the program bus.
4 Transition type or rate.
Changes
It is not possible to change the source of an effect until the effect is off the program bus.
Hot Cuts
A “hot cut” occurs when an operator switches a main source, video effect, or audio over directly on
the program bus, without executing a transition.
If the MCPM is in transition and a “hot cut” is requested, the MCPM cancels the transition and the
following will occur immediately:
1 Any video effects that were “on” prior to the transition on both the program and preset buses
will be left “on.” All other video effect will be “off” on the program bus.
2 If the same audio over was “on” prior to the transition on both the program and preset buses, it
will be left “on.” Otherwise all audio overs will be “off” on the program bus.
3 The program output will switch to the selected source.
Caution
You can expect video and audio artifacts when operators perform hot cuts.
A hot cut (on the program bus) is unlike a transition (even a cut transition). In a tran-
sition, video and audio signals are already acquired on the preset bus and the pro-
gram bus prior to the transition.
In a hot cut, the program bus must acquire a new signal. This time required for the
reacquisition is approximately 4 or 5 lines of video. Ancillary data, such as AFD,
can be lost because the video processor cannot acquire it in time. If it does lose
ancillary data, the video processor will get the data in the next frame, but the video
will suffer for one frame. (Without AFD, for example, the video can appear with the
wrong aspect ratio.)
In a hot cut, the audio disembedder takes about 1/2 frame to re-sync. Audio disconti-
nuities (glitches) are perceptible.
Although the MCPM or MCE can recover in one frame or less, other downstream
equipment might not be able to recover the signal as quickly. If the AFD information
is lost, a frame synchronizer or aspect ratio converter can require a significant num-
ber of frames to adjust to the new video signal and its format. Dolby E decoders can
require several seconds to re-sync.
Operators may correct problems with hot cuts, but must expect a certain amount of
time for the on-air signal to re-sync, up to several seconds, depending on the equip-
ment installed.
In summary: do not perform hot cuts unless you must correct a serious problem.