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IWMEncDeviceControlPlugin::get_PreRoll

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The get_PreRoll method retrieves the number of frames that you want a device to play before encoding begins.

Syntax

HRESULT get_PreRoll(
  long*  plPreroll
);

Parameters

plPreroll

[out]  Pointer to a long containing the number of frames to preroll.

Return Values

If the method succeeds, it returns S_OK. If it fails, it supports the IErrorInfo interface and returns an HRESULT error code.

Return code Number Description
E_POINTER 0x80004003 The pointer to the preroll value is NULL.

Remarks

This value is relative to the mark-in time. Pre-rolling the tape enables it to stabilize so that lines, jitters, or other artifacts resulting from the startup of the device are not encoded.

Requirements

Header: wmdevctl.h

Library: wmdevctl.dll

See Also