IWMIStreamProps::GetProperty method (wmsdkidl.h)

Artigo
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 It has been superseded by Source Reader and Sink Writer.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 GetProperty method retrieves a named property from the IStream.

Syntax

HRESULT GetProperty(
  [in]      LPCWSTR           pszName,
  [out]     WMT_ATTR_DATATYPE *pType,
  [out]     BYTE              *pValue,
  [in, out] DWORD             *pdwSize
);

Parameters

[in] pszName

Pointer to a null-terminated string containing the name of the property to retrieve. You should use the global identifier to refer to properties so that any error will appear at compile time. The following table lists the available IStream properties.

Property name	Global identifier
ReloadIndexOnSeek	g_wszReloadIndexOnSeek
StreamNumIndexObjects	g_wszStreamNumIndexObjects
FailSeekOnError	g_wszFailSeekOnError
PermitSeeksBeyondEndOfStream	g_wszPermitSeeksBeyondEndOfStream
UsePacketAtSeekPoint	g_wszUsePacketAtSeekPoint
SourceBufferTime	g_wszSourceBufferTime
SourceMaxBytesAtOnce	g_wszSourceMaxBytesAtOnce

[out] pType

Pointer to a variable that will receive one member of the WMT_ATTR_DATATYPE enumeration type. This value indicates the type of data in the buffer at pValue.

[out] pValue

Pointer to a byte buffer that will receive the property value. The type of data returned to the buffer is indicated by the value pointed to by pType.

[in, out] pdwSize

Pointer to a DWORD containing the size of the buffer at pValue. On return, this value will be set to the correct size of the property value.

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_INVALIDARG	pType, pValue, or pdwSize is NULL. OR The buffer is not big enough to hold the requested value.
E_FAIL	pszName specifies an invalid property name.

Return code

Description

S_OK

The method succeeded.

E_INVALIDARG

pType, pValue, or pdwSize is NULL.

The buffer is not big enough to hold the requested value.

E_FAIL

pszName specifies an invalid property name.

Remarks

You should make two calls to GetProperty for each property you want to retrieve. On the first call, pass NULL as pValue. On return, the value pointed to by pdwSize will be set to the buffer size required to hold the property value. Then you can allocate the required amount of memory for the buffer and pass a pointer to it as pValue on the second call.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only],Windows Media Format 9 Series 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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