IVMRMixerControl9::GetAlpha method (vmr9.h)

项目
4/26/2023

[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 It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation.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. This value corresponds to the input pin. For example, the first input pin is stream 0.

[out] pAlpha

Pointer to a variable that receives the current alpha value.

Return value

The method returns an HRESULT. Possible values include those in the following table.

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

Remarks

Include DShow.h and D3d9.h before Vmr9.h.

Requirements

Requirement	Value
Minimum supported client	Windows XP with SP2 [desktop apps only]
Minimum supported server	Windows Server 2003 R2 [desktop apps only]
Target Platform	Windows
Header	vmr9.h
Library	Strmiids.lib

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