Grass Valley Imagestore 750 v.3.0.1 - Manual (Page 72)

56
Features
Closed Captions
The co-processor completes any out-transitions and then cuts down its first layer.
The Imagestore 750 receives a ‘30 0’ tally command from the co-processor, but does nothing
with its own keying layers because there is still one co-processor layer active.
4 Cut down the final visible layer of the co-processor ‘36 0’.
The Imagestore 750 maps the command ‘6 0’ to ‘32 0’ and forwards it to the co-processor.
The co-processor completes any out-transitions and then cuts down its third layer.
The Imagestore 750 receives a ‘32 0’ tally command from the co-processor, and then cuts
down DSK 1 because there are no co-processor layers active.
Note that ‘Default Keyer Assign’ can be cut down (or up) at any point to override the automatic
keyer management.
 In the master control environment, we recommend that ‘Keyer Follow Up’ be disabled so
that Intuition XG graphics can be previewed by iMC panel users without automatically
appearing on-air. Automation then must be responsible for cutting up the assigned DSK
with Intuition XG layers.
Closed Captions
Closed caption information is usually passed through the Imagestore 750 regardless of what the
closed caption option is. The reason for the option is that when the standard is set as NTSC (525),
closed caption information is found within the active picture (lines 20 and 21), and it will be
destroyed when graphics are keyed over these lines.
When the closed caption option is enabled ( Setup > Miscellaneous > Closed Cap at the
front panel menu), the Imagestore 750 ensures that the close caption information is preserved
regardless of keyed graphics being present on lines 20 and 21. Disabling the option instructs the
keyers and mixers to treat these lines as part of the active picture so that they may be mixed
with the key.
For HD, closed caption information is contained in vertical ancillary data (VANC) on line 9, which
is outside the active picture. Because this information is never processed by the keyers, the
closed caption information is preserved, regardless of the option selected.
Please note that when an SDI picture is routed to a DVE, the closed caption information might
be visible at the top of the DVE window. To avoid this problem, we recommend that all DVE
sequences be cropped by 2.5% at the top to remove this undesirable effect.
Timecode
The following timecode formats are supported by the Imagestore 750:
• Linear (or longitudinal) timecode (LTC).
Received on the GPI/LTC port (or its 44-pin terminal block adaptor). (See GPIO / LTC on
page 207.)
Supports dropframe and non-dropframe.
Supports forward and backward directions.
• Vertical interval timecode (VITC).
Received from the external reference.
Supports dropframe and non-dropframe.