IWMHeaderInfo3::GetAttributeIndices method (wmsdkidl.h)

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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 It has been superseded by Source Reader and Sink Writer.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 GetAttributeIndices method retrieves a list of valid attribute indices within specified parameters. You can retrieve indices for all attributes with the same name or for all attributes in a specified language. The indices found are for a single specific stream. Alternatively, you can retrieve the specified indices for the entire file.

Syntax

HRESULT GetAttributeIndices(
  [in]      WORD    wStreamNum,
  [in]      LPCWSTR pwszName,
  [in]      WORD    *pwLangIndex,
  [out]     WORD    *pwIndices,
  [in, out] WORD    *pwCount
);

Parameters

[in] wStreamNum

WORD containing the stream number for which to retrieve attribute indices. Passing zero retrieves indices for file-level attributes. Passing 0xFFFF retrieves indices for all appropriate attributes, regardless of their association to streams.

[in] pwszName

Pointer to a wide-character null-terminated string containing the attribute name for which you want to retrieve indices. Pass NULL to retrieve indices for attributes based on language. Attribute names are limited to 1024 wide characters.

[in] pwLangIndex

Pointer to a WORD containing the language index of the language for which to retrieve attribute indices. Pass NULL to retrieve indices for attributes by name.

[out] pwIndices

Pointer to a WORD array containing the indices that meet the criteria described by the input parameters. Pass NULL to retrieve the size of the array, which will be returned in pwCount.

[in, out] pwCount

On output, pointer to a WORD containing the number of elements in the pwIndices array.

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.
NS_E_SDK_BUFFERTOOSMALL	The size specified in pwCount is too small.
NS_E_INVALID_REQUEST	wStreamNum is not a valid stream number, pwLangIndex is not a valid language index, or pwszName is not a valid name.
E_POINTER	A pointer is not valid.

Remarks

You must make two calls to GetAttributeIndices for each set of indices retrieved. On the first call, pass NULL as pwIndices. On return, the variable pointed to by pwCount is set to the number of elements required for the array of indices. Then allocate memory for the array and make the second call, passing a pointer to the array as pwIndices.

If you use 0xFFFF for the stream number, the index values returned will be global indices. Only use a global index for calls to other methods of the IWMHeaderInfo3 interface if you will also be using 0xFFFF for the stream number. The global index value for an attribute will be different than the value used when specifying a specific stream number (or stream 0 for file-level attributes).

Index values obtained by using this method are given in descending order by index. This is to aid in deleting attributes, which should always be done in descending order.

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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