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The IDsCaptureDriverBuffer::Lockmethod is called to obtain a valid read pointer to the sound buffer's audio data.
HRESULT Lock( LPLPVOID ppvAudio1 , LPDWORD pdwLen1 , LPLPVOID ppvAudio2 , LPDWORD pdwLen2 , DWORD dwWritePosition , DWORD dwWriteLen , DWORD dwFlags );
Parameters
Return Values
Returns DS_OK if successful, or one of the following error values otherwise:
Remarks
This method accepts an offset and a count of bytes, and the driver returns two write pointers and their associated sizes. Two pointers are required because sound buffers are circular. If the locked bytes do not wrap around the end of the buffer, the second pointer ( *ppvAudio2) should be NULL. However, if the bytes do wrap around, the second pointer should point to the beginning of the buffer.
For some devices (such as DMA-based cards that do not support hardware secondary buffers), repeated calls to IDsCaptureDriverBuffer::Lockand IDsCaptureDriverBuffer::Unlockare unnecessary. In this case, the driver should specify the DSDCAPS_DONTNEEDLOCK flag in the DSDRIVERDESCstructure returned by IDsCaptureDriver::GetDriverDescmethod. If this flag is specified, then the IDsCaptureDriverBuffer::Lockmethod is never called by DirectSound. In that case, the IDsCaptureDriverBuffer::Lockmethod should simply return DSERR_UNSUPPORTED.
Last updated on Tuesday, July 13, 2004
© 2004 Microsoft Corporation. All rights reserved.