|Microsoft DirectX 9.0|
The AllocateSurface method allocates a DirectDraw surface.
HRESULT AllocateSurface( DWORD_PTR dwUserID, VMRALLOCATIONINFO* lpAllocInfo, DWORD* lpdwActualBuffers, LPDIRECTDRAWSURFACE7* lplpSurface );
[in] An application-defined DWORD_PTR cookie that uniquely identifies this instance of the VMR for use in scenarios when one instance of the allocator-presenter is used with multiple VMR instances.
[in] Specifies the VMRALLOCATIONINFO structure. See Remarks.
[in] [out] On input this parameter is used to request the number of buffers desired. On output it receives the actual number of buffers created.
[out] Address of a pointer that receives the Direct3D surface.
If the method succeeds, it returns S_OK. If it fails, it returns an error code.
|E_POINTER||One of the pointers is invalid.|
|E_INVALIDARG||In dwFlags, the AMAP_3D_TARGET was combined with AMAP_FORCE_SYSMEM or AMAP_ALLOW_SYSMEM.|
|E_FAIL||One or more members of the BITMAPINFOHEADER structure specified by lpAllocInfo->lpHdr is incorrect.|
Before calling AllocateSurface explicitly, a client application should call IVMRSurfaceAllocator::FreeSurface to be sure that the DirectDraw decoding surface front buffer is NULL. If it is not NULL at the time an application calls AllocateSurface, the debug version of quartz.dll will cause an assertion.
When implementing this method in a custom allocator-presenter, you must examine the value of lpAllocInfo->lpHdr->biBitCount. If biBitCount is zero, then you must set it to the pixel depth for the current display. If BiBitCount is left at zero, the surface allocation will fail and a new (default) VMR will be created.