ViewCast Osprey-450e - Manual (Page 34)

Setting Driver Properties
28 ViewCast
of the displayed video. In films and analog broadcast video, however, lines 21 and 284 are often
used for Closed Caption. In broadcast video, lines 22 and 285 are sometimes used for proprietary
ancillary data. If these lines are used for data they will appear as moving bands or streaks across the
top lines. Therefore, the most generally useful start lines are 23 / 286.
Some broadcast video also uses additional top line pairs for ancillary data. We are seeing cases
where the top line has to be set to lines 26 / 289 in order to hide all the data lines.
You can set start lines all the way up to 27 / 290. (On the PCI products which have a Direct Mode
option, PostProcessing Mode must be set in order to have top lines below 23 / 286.)
When the start lines are below 23 / 286, the bottom of the video frame spills off the bottom of the
485-line NTSC-standard frame. In this case the driver adds black lines at the bottom of the frame.
Note: If you select start line 21 / 284, Closed Captions cannot be decoded. On the Osprey-
240e/450e, CC cannot be decoded if the start lines are 22 / 285 as well as 21 / 284.
Changes to this control take effect only when all video streams are stopped and restarted. All
streams must be stopped before any are restarted.