IWMReader::Open method (wmsdkidl.h)

Статья
4/26/2023

[The feature associated with this page, Windows Media Format 11 SDK, is a legacy feature. It has been superseded by Source Reader and Sink Writer. Source Reader and Sink Writer have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Source Reader and Sink Writer instead of Windows Media Format 11 SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The Open method opens an ASF file for reading.

Syntax

HRESULT Open(
  [in] const WCHAR       *pwszURL,
  [in] IWMReaderCallback *pCallback,
  [in] void              *pvContext
);

Parameters

[in] pwszURL

Pointer to a wide-character null-terminated string containing the path and name of the file to be opened. This method accepts a path to a folder on a local machine, a path to a network share, or a uniform resource locator (URL).

[in] pCallback

Pointer to the object that implements the IWMReaderCallback interface.

[in] pvContext

Generic pointer, for use by the application. This is passed to the application in calls to OnStatus.

Return value

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Return code	Description
S_OK	The method succeeded.
E_POINTER	The pCallback parameter is NULL.
E_OUTOFMEMORY	There is not enough available memory.
E_UNEXPECTED	The method failed for an unspecified reason.

Remarks

This method is asynchronous; it returns very quickly and sends a WMT_OPENED status notification to the application's IWMStatusCallback::OnStatus method when the file is opened and ready for use.

Because the method returns before the file is opened, a return value of S_OK does not necessarily mean that the file has been opened successfully. To ascertain the success of the call, you must check the value of the hr parameter of OnStatus when the WMT_OPENED notification is received.

If hr equals NS_E_NO_STREAM it means that the header is not yet available, and that a WMT_SOURCE_SWITCH event will be sent as soon as the header becomes available. No WMT_EOF will be sent before the WMT_SOURCE_SWITCH.

Applications that read files from behind a firewall will have better performance when opening files if the address is specified using the domain name server (DNS) name instead of the IP address.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only],Windows Media Format 7 SDK, or later versions of the SDK
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	wmsdkidl.h (include Wmsdk.h)
Library	Wmvcore.lib; WMStubDRM.lib (if you use DRM)

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