AVStream Driver Reference Information
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Vertical Blanking Interval (VBI) Capture
The Osprey 530/540/560 does not support VBI raw capture. It only supports decoded capture of the
two special streams, Closed Caption (CC) and vertical interval timecode (VITC). If your application
requires VBI capture for WST teletext decoding or other purposes, and you are using analog inputs,
you can use an Osprey 100 or 200 series device instead.
The Osprey AVStream driver provides DirectShow-compatible VBI pins. VBI data includes Vertical
Interval Timecode (VITC) in both the NTSC and PAL worlds. In NTSC, line 21 Closed Captioning,
(although it is part of the video interval rather than true VBI data) is commonly treated as VBI data.
In PAL, World Standard Teletext (WST) is encoded in the VBI data region.
The driver delivers VBI data as raw waveforms, which are then decoded by external DirectShow
filters. DirectShow provides three filters under the classification “WDM Streaming VBI Codecs” that
will decode data from VBI pins:
CC Decoder
NABTS/FEC VBI Codec
WST Codec
With the Osprey AVStream driver, either the CC pin or the VBI pin can be used to obtain closed
caption data. If the VBI pin is used, an extra filter is required to turn the raw waveform into CC
character pairs. The filtergraph below shows NTSC CC using the VBI pin; the graph in the CC section
above shows CC from the CC pin; in the graph below, a CC Decoder filter must be inserted into the
graph.
For PAL/SECAM, the following graph will display teletext and CC. (In this graph, to view CCs you have
to select the CC page – probably page 801 - in the WST Decoder properties.)
When SimulStream is not installed, the driver supports two VBI pin instances. In practice, a
DirectShow Smart Tee Filter can be inserted into the graph to make any number of VBI pins. When
SimulStream is installed, any number of VBI pins is allowed.
Summary of Contents for Osprey PCI
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Page 29: ...Osprey PCI User Guide ViewCast 23 Figure 15 VbiGraph utility...
Page 56: ...Setting Driver Properties 50 ViewCast Figure 35 Extras...
Page 67: ...Osprey PCI User Guide ViewCast 61 Figure 46 Weighting...
Page 70: ...Setting Driver Properties 64 ViewCast...
Page 77: ...Osprey PCI User Guide ViewCast 71...
Page 107: ...Osprey PCI User Guide ViewCast 101...
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Page 118: ...Appendix C Troubleshooting 112 ViewCast...
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