IWMHeaderInfo3::ModifyAttribute method (wmsdkidl.h)

Artikel
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 It has been superseded by Source Reader and Sink Writer.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 ModifyAttribute method modifies the settings of an existing attribute.

Syntax

HRESULT ModifyAttribute(
  [in] WORD              wStreamNum,
  [in] WORD              wIndex,
  [in] WMT_ATTR_DATATYPE Type,
  [in] WORD              wLangIndex,
  [in] const BYTE        *pValue,
  [in] DWORD             dwLength
);

Parameters

[in] wStreamNum

WORD containing the stream number to which the attribute applies. Pass zero for file-level attributes.

[in] wIndex

WORD containing the index of the attribute to change.

[in] Type

Type of data used for the new attribute value. For more information about the types of data supported, see WMT_ATTR_DATATYPE.

[in] wLangIndex

WORD containing the language index of the language to be associated with the new attribute. This is the index of the language in the language list for the file.

[in] pValue

Pointer to an array of bytes containing the attribute value.

[in] dwLength

DWORD containing the length of the attribute value, in bytes.

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	An illegal parameter combination, data type, or attribute name was used.
E_NOTIMPL	The method is not implemented on a reader object.
E_POINTER	A pointer is not valid.
NS_E_ATTRIBUTE_READ_ONLY	The attribute cannot be changed.
NS_E_INVALID_REQUEST	wStreamNum is not a valid stream number, or there is no attribute at wIndex.

Remarks

You can use 0xFFFF for the stream number to specify an attribute using its global index. Global index values range from 0 to one less than the count of attributes received from a call to IWMHeaderInfo3::GetAttributeCountEx where the stream number was set to 0xFFFF.

When setting attributes for MP3 files, the metadata editor will automatically insert a byte-order mark in accordance with the Unicode specification. If you manually insert a byte-order mark, this method will not fail, but the value will then have two marks, which can cause problems when reading the attribute.

The objects of the Windows Media Format SDK perform type checking on some supported metadata attributes, but not all of them. You should ensure that any attributes you use are set using the data type specified in the Attributes section of this documentation. Likewise, you cannot assume that an attribute set by another application will use the correct data type.

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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