Performs a synchronous read.

LONGLONG llPosition,
LONG lLength,
BYTE* pBuffer);


  • llPosition
    [in] Absolute file position.
  • lLength
    [in] Number of bytes required.
  • pBuffer
    [out] Where the data is written.

Return Values

Returns an HRESULT value that depends on the implementation of the interface. Current DirectShow implementation return values include:

Value Description
VFW_E_BADALIGN An invalid alignment was specified.
HRESULT_FROM_WIN32 Win32 error.
S_FALSE Size changed (probably due to end of file).
S_OK Success.


The SyncRead method works in a stopped state as well as in a running state. The read is not necessarily aligned. This method fails if the read is beyond the actual total length.

 Last updated on Tuesday, July 13, 2004

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