ViewCast Osprey-450e - Manual (Page 77)

Osprey 240e/450e User Guide
ViewCast 71
CC streaming interface
The driver supports an Osprey custom property which provides the closed caption character stream
for use by custom applications. The Osprey filter named CCLineInterp.ax, supplied with the driver
package, provides user-mode support for this captioning mode. The Osprey sample applet named
CCChannels.exe, also supplied with the driver package, demos a CC line interpreter and XDS (vchip)
extraction and display. Both the filter and the applet are provided in source code form in the SDK.
Vertical Interval Timecode (VITC)
Vertical Interval Timecode (VITC) data is embedded in the Vertical Blanking Intervals (VBIs) of some
video content. Timecodes mark each frame with an hour / minute / second / frame number marking
that can be use for frame-precise editing.
Figure 60. ActiveMovie Window
The current Osprey VITC implementation is preliminary in nature. The features and method of
implementation are subject to change. We invite comments on the timecode-related capabilities
that you need for your application.
Osprey’s approach to VITC is to invisibly watermark the video bits of each outgoing video frame with
its timestamp data. The illustration shows a timecode extracted from a watermarked frame and
rendered as text on the video. Four elements are used to produce it:

The device extracts timecode data from the vertical blanking interval (VBI) waveform.

The driver watermarks timecode into the video preview or capture pin’s output data.

A custom filter decodes the watermark from the video and renders it.

A GraphEdit graph combines the required filters.
The Osprey Timecode Filter resides in the module TCOverlay.ax and is installed and registered as
part of the standard driver installation. The source code for this filter is included in the Osprey
AVStream SDK.
The Osprey Timecode Filter also exposes to applications a custom property and callback function
that allows it to return the VITC data for each frame along with the frame’s timestamp to the