CBaseFilter.GetState method

Article
07/27/2023

[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 It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation.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 GetState method retrieves the filters's state (running, stopped, or paused). This method implements the IMediaFilter::GetState method.

Syntax

HRESULT GetState(
   DWORD        dwMilliSecsTimeout,
   FILTER_STATE *State
);

Parameters

dwMilliSecsTimeout: Time-out interval, in milliseconds.
State: Pointer to a variable that receives a member of the FILTER_STATE enumerated type, indicating the filter's state.

Return value

Returns S_OK or E_POINTER.

Remarks

In the base class, all state transitions are synchronous and the dwMilliSecsTimeout parameter is ignored. If a derived class performs asynchronous state transitions, it should override this method to wait during state transitions, with a time-out of dwMilliSecsTimeout milliseconds.

If your filter does not deliver data while paused, override the GetState method to return the value VFW_S_CANT_CUE when the filter is paused (see Delivering Samples). For example:

CMyFilter::GetState(DWORD dw, FILTER_STATE *pState)
{
    CheckPointer(pState, E_POINTER);
    *pState = m_State;
    if (m_State == State_Paused)
        return VFW_S_CANT_CUE;
    else
        return S_OK;
}

Requirements

Requirement	Value
Header	Amfilter.h (include Streams.h)
Library	Strmbase.lib (retail builds); Strmbasd.lib (debug builds)