IMediaSeeking::CheckCapabilities method (strmif.h)

项目
10/21/2021
2 分钟可看完

The CheckCapabilities method queries whether a stream has specified seeking capabilities.

Syntax

HRESULT CheckCapabilities(
  [in, out] DWORD *pCapabilities
);

Parameters

[in, out] pCapabilities

On input, a pointer to a variable that contains a bitwise OR of one or more AM_SEEKING_SEEKING_CAPABILITIES attributes. When the method returns, the value indicates which of those attributes are available.

Return value

Returns an HRESULT value. Possible values include the following.

Return code	Description
S_FALSE	Some but not all of the capabilities in pCapabilities are present.
S_OK	All capabilities in pCapabilities are present.
E_FAIL	No capabilities in pCapabilities are present.
E_POINTER	NULL pointer argument.

Remarks

If you are only interested in a few specific capabilities, calling this method is more efficient than calling IMediaSeeking::GetCapabilities, which checks all the stream's seeking capabilities.

To call this method, declare a DWORD variable and set the value to the bitwise-OR combination of the AM_SEEKING_SEEKING_CAPABILITIES flags that you want to test. Pass the address of this value in the pCapabilities parameter. When the method returns, pCapabilities contains a subset of the original bits, indicating which capabilities are present. The return value indicates whether some, none, or all of the requested capabilities are present.

The following code example shows how to find out whether the stream supports forward seeking, backward seeking, and absolute seeking.

C++
// Set flags for the capabilities you want to check. DWORD dwCaps = AM_SEEKING_CanSeekAbsolute \| AM_SEEKING_CanSeekForwards \| AM_SEEKING_CanSeekBackwards; HRESULT hr = pMediaSeeking->CheckCapabilities(&dwCaps); if(FAILED(hr)) { // The stream cannot seek. } else if (hr == S_OK) { // The stream can seek forward, backward, and to an absolute position. } else if (hr == S_FALSE) // The stream has some of the capabilities. { if (dwCaps & AM_SEEKING_CanSeekAbsolute) { // The stream can seek to an absolute position. } if (dwCaps & AM_SEEKING_CanSeekForwards) { // The stream can seek forward. } if (dwCaps & AM_SEEKING_CanSeekBackwards) { // The stream can seek backward. } }

C++

// Set flags for the capabilities you want to check.
DWORD dwCaps = AM_SEEKING_CanSeekAbsolute |
AM_SEEKING_CanSeekForwards |
AM_SEEKING_CanSeekBackwards;
HRESULT hr = pMediaSeeking->CheckCapabilities(&dwCaps);
if(FAILED(hr))
{
// The stream cannot seek.
}
else if (hr == S_OK)
{

// The stream can seek forward, backward, and to an absolute position.
}
else if (hr == S_FALSE) // The stream has some of the capabilities.
{
if (dwCaps & AM_SEEKING_CanSeekAbsolute)
{
// The stream can seek to an absolute position.
}
if (dwCaps & AM_SEEKING_CanSeekForwards)
{
// The stream can seek forward.
}
if (dwCaps & AM_SEEKING_CanSeekBackwards)
{
// The stream can seek backward.
}
}

Requirements


Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	strmif.h (include Dshow.h)
Library	Strmiids.lib