IMemAllocator::GetBuffer

  • Article

This method retrieves a container for a sample.

HRESULT GetBuffer(
  IMediaSample** ppBuffer,
  REFERENCE_TIME* pStartTime,
  REFERENCE_TIME* pEndTime,
  DWORD dwFlags
);

Parameters

  • ppBuffer
    [out] Pointer to a retrieved media sample buffer.
  • pStartTime
    [in] Either NULL or set to the beginning time of the sample to retrieve. Only the video renderer uses this.
  • pEndTime
    [in] Either NULL or set to the ending time of the sample to retrieve. Only the video renderer uses this.
  • dwFlags
    [in] GetBuffer supports the following flags.
    Flag Description
    AM_GBF_NOTASYNCPOINT Dynamic format changes are not allowed on this buffer because it is not a key frame.
    AM_GBF_PREVFRAMESKIPPED Set to TRUE if this sample is the first after a discontinuity. Only the video renderer uses this.

Return Values

Returns an HRESULT value that depends on the implementation. HRESULT can be one of the following standard constants, or other values not listed.

Value Description
E_FAIL Failure.
E_POINTER Null pointer argument.
E_INVALIDARG Invalid argument.
E_NOTIMPL Method is not supported.
S_OK or NOERROR Success.

Remarks

IMemAllocator::GetBuffer is a locking, synchronous method to get the next free buffer. Upon return, the properties are invalid, but the buffer pointer and size are correct. This method succeeds only if memory has been committed. GetBuffer returns with an error value if it is blocked waiting for a buffer, and the IMemAllocator::Decommit method is called on another thread.

If the pStartTime and pEndTime parameters are not NULL, they specify the intended start and end time for the sample in stream time (reference clock time minus the stream time offset). The video renderer applies these parameters when using DirectDraw to schedule when to return a sample. If pStartTime and pEndTime are NULL the video renderer will not use DirectDraw.

Requirements

DirectShow applications and DirectShow filters have different include file and link library requirements. See Setting Up the Build Environment for more information.

OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.

See Also

IMemAllocator Interface

Last updated on Wednesday, April 13, 2005

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