AVStream Driver Reference Information
This capability requires custom programming. Refer to the Osprey AVStream SDK Users’ Guide. A sample SDK applet named TCApp illustrates the interface.
Figure 69. Timecode Video Marking
Timecode stamping must be enabled in the driver before it can be used, and the field and line number correctly set. To access the controls, go to the Device property tab and click Extras.
It is recommended that you disable timecode marking when not in use, especially the auto search feature (on a slow machine it uses several percent of CPU bandwidth) especially if timecodes are not present.
Note: VITC and LTC – Longitudinal Timecode – are two distinct encoding systems, and this driver supports only VITC.
A suggested reference on timecode is Timecode: a user’s guide – 3rd ed., John Ratcliff, Focal Press, 1999.
Vertical Blanking Interval (VBI) capture
The Osprey AVStream driver provides
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, you can use either the CC pin or the VBI pin to obtain closed caption data. If you use the VBI pin, an extra filter is required to turn the raw waveform into CC character pairs.
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, multiple VBI pins are allowed.
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