Data Translation 18729, Руководство пользователя

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Chapter 2
22
Passthru Operations
In a passthru operation, a DT3120 board continuously captures and
displays video data until you stop the operation. Typically, you use
passthru to view images (in as close to real time as possible for the
configuration and passthru method chosen) for the purpose of
focusing or positioning the camera.
In addition to displaying passthru data, you can continuously store
the data to user-allocated buffers in host memory, if desired. This
operation is called continuous-acquire passthru mode.
This section describes the following aspects of passthru:
• Passthru modes,
• Source origin,
• Passthru scaling, and
• Overlays.
Passthru Modes
The DT3120 board supports bitmap passthru mode and
continuous-acquire passthru mode. This section describes these
modes.
Bitmap Passthru Mode
The DT3120 board supports asynchronous bitmap passthru mode.
In an asynchronous operation, the operation starts but gives control
to you immediately, allowing you to perform other operations while
data is displayed.
Bitmap passthru mode requires a frame in device memory into which
the image is captured.