CSourceSeeking.CheckCapabilities 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 It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation.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 CheckCapabilities method queries whether the stream has specified seeking capabilities. This method implements the IMediaSeeking::CheckCapabilities method.

Syntax

HRESULT CheckCapabilities(
   DWORD *pCapabilities
);

Parameters

pCapabilities: Pointer to a bitwise combination of one or more AM_SEEKING_SEEKING_CAPABILITIES attributes.

Return value

Returns one of the HRESULT values listed in the following table.

Return code	Description
S_FALSE	Not all of the capabilities in pCapabilities are present.
S_OK	All capabilities in pCapabilities are present.
E_POINTER	NULL pointer argument.

Remarks

As implemented, this method checks the value of *pCapabilities against the CSourceSeeking::m_dwSeekingCaps member variable. However, it does not set *pCapabilities equal to m_dwSeekingCaps, as described for the IMediaSeeking::CheckCapabilities method. Also, in the case where none of the specified capabilities are available, the method does not return E_FAIL. A more complete implementation would be as follows:

STDMETHODIMP CheckCapabilities(DWORD *pCapabilities)
{
    CheckPointer(pCapabilities, E_POINTER)
;
    DWORD dwCaps;
    HRESULT hr = GetCapabilities(&dwCaps);
    if (SUCCEEDED(hr))
    {
        dwCaps &= *pCapabilities;
        if (dwCaps)
        {
            hr =  (dwCaps == *pCapabilities ? S_OK : S_FALSE );
        }
        else 
        {
            hr = E_FAIL;
        }
        *pCapabilities = dwCaps;
    }
    else 
    {
        *pCapabilities = 0;
    }
    return hr;
}

Requirements

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