IWMHeaderInfo::SetAttribute method (wmsdkidl.h)

Artículo
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 It has been superseded by Source Reader and Sink Writer.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 SetAttribute method sets a descriptive attribute that is stored in the header section of the ASF file. This method is replaced by IWMHeaderInfo3::AddAttribute, and should not be used.

Syntax

HRESULT SetAttribute(
  [in] WORD              wStreamNum,
  [in] LPCWSTR           pszName,
  [in] WMT_ATTR_DATATYPE Type,
  [in] const BYTE        *pValue,
  [in] WORD              cbLength
);

Parameters

[in] wStreamNum

WORD containing the stream number. To set a file-level attribute, pass zero.

[in] pszName

Pointer to a wide-character null-terminated string containing the name of the attribute. Attribute names are limited to 1024 wide characters.

[in] Type

A value from the WMT_ATTR_DATATYPE enumeration type.

[in] pValue

Pointer to a byte array containing the value of the attribute.

[in] cbLength

The size of pValue, 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	A parameter does not contain a valid value.
E_NOTIMPL	Not implemented.
E_UNEXPECTED	The method failed for an unspecified reason.
NS_E_INVALID_STATE	The object is not in a configurable state, or no profile has been set.

Remarks

Refer to the Attributes section for a list of predefined attributes. For predefined attributes, the Type parameter must match the data type defined for that attribute. For custom attributes, you can specify any type except WMT_TYPE_GUID, but the buffer size (given by cbLength) must match the type. See WMT_ATTR_DATATYPE for more information.

The IWMHeaderInfo interface does not support the WMT_TYPE_GUID data type. To use this data type, you must use the methods of the IWMHeaderInfo3 interface.

Attributes in MP3 files cannot be specific to a particular stream. For MP3 files, always set the stream number to zero. 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.

This method does not support attributes with values larger than 64 kilobytes. To include large attributes in your file, use the methods of the IWMHeaderInfo3 interface.

The writer object supports this method only before the IWMWriter::BeginWriting method has been called. The reader and synchronous reader objects do not support this method.

Before you can use this method through the IWMHeaderInfo interface of a writer object to set DRM attributes, you must set a profile for the writer to use.

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 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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