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IVMRMixerControl::GetAlpha method (strmif.h)

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[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The GetAlpha method retrieves the constant alpha value that is applied to this video stream.

Syntax

HRESULT GetAlpha(
  [in]  DWORD dwStreamID,
  [out] float *pAlpha
);

Parameters

[in] dwStreamID

Specifies the input stream.

[out] pAlpha

Pointer to a variable of type float that receives the current alpha value.

Return value

If the method succeeds, it returns S_OK. If it fails, it returns an error code.

Return code Description
E_POINTER
 pAlpha is invalid.
VFW_E_NOT_CONNECTED
 The pin is not connected.

Requirements

Requirement Value
Minimum supported client Windows XP with SP1 [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Target Platform Windows
Header strmif.h (include Dshow.h)
Library Strmiids.lib

See also

Error and Success Codes

IVMRMixerControl Interface

IVMRMixerControl::SetAlpha

Using the Video Mixing Renderer