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IDMOVideoOutputOptimizations interface (mediaobj.h)

  • Articolo

[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 It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation.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 IDMOVideoOutputOptimizations interface supports video optimizations on a Microsoft DirectX Media Object (DMO).

Inheritance

The IDMOVideoOutputOptimizations interface inherits from the IUnknown interface. IDMOVideoOutputOptimizations also has these types of members:

Methods

The IDMOVideoOutputOptimizations interface has these methods.

 
IDMOVideoOutputOptimizations::GetCurrentOperationMode

The GetCurrentOperationMode method retrieves the optimization features in effect.
IDMOVideoOutputOptimizations::GetCurrentSampleRequirements

The GetCurrentSampleRequirements method retrieves the optimization features required to process the next sample, given the features already agreed to by the application.
IDMOVideoOutputOptimizations::QueryOperationModePreferences

The QueryOperationModePreferences method retrieves the DMO's preferred optimization features.
IDMOVideoOutputOptimizations::SetOperationMode

The SetOperationMode method notifies the DMO of the optimization features that are in effect.

Remarks

This interface enables an application to negotiate with a DMO about video output optimizations. A DMO exposes this interface when it can perform optimizations that require support from the application. The application can query the DMO for its preferred features, and then agree (or not agree) to provide them. The DMO must process output even if the application rejects the optimizations.

For example, a video decoder might generate an output frame by applying deltas to the previous output frame. When queried, it requests that the application supply the previous frame in the output buffer. The application can agree to this request or not.

Video optimizations are negotiated separately for each output stream.

The following pseudo-code shows how an application might negotiate with the DMO:

IDMOVideoOutputOptimizations *pVidOpt;
// Query the DMO for IDMOVideoOutputOptimizations (not shown).

BOOL  bWantsPreviousBuffer = FALSE;
DWORD wFlags;
pVidOpt->QueryOperationModePreferences(0,&dwFlags);

if (dwFlags & DMO_VOSF_NEEDS_PREVIOUS_SAMPLE) 
{
    // Agree to the request.      
    pVidOpt->SetOperationMode(0, DMO_VOSF_NEEDS_PREVIOUS_SAMPLE);
    bWantsPreviousBuffer = TRUE;
}

// Processing loop
while (there is input).
{
    ProcessInput(0, ...);
    if (bWantsPreviousBuffer)
        pDMO->ProcessOutput(0, ...) // Use the same buffer as last time.
    else
        pDMO->ProcessOutput(0, ...) // OK to use a new buffer.
}

Requirements

Requirement Value
Target Platform Windows
Header mediaobj.h (include Dmo.h)