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MF_PD_ASF_CODECLIST attribute

Contains information about the codecs and formats that were used to encode the content in an Advanced Systems Format (ASF) file. This attribute corresponds to the Codec List Object in the ASF header, defined in the ASF specification.

Data type

Byte array

Remarks

This attribute applies to presentation descriptors for ASF content.

The IMFASFContentInfo::GeneratePresentationDescriptor method creates the presentation descriptor and generates this attribute from the Codec List Object in the ASF header. An application that uses the ASF Media Source can get this attribute by calling IMFMediaSource::CreatePresentationDescriptor and then getting the attribute from the presentation descriptor.

The following table shows the layout of the attribute blob.

Codec List Object fieldData typeSizeDescription
Codec Entries CountDWORD4 bytesNumber of codecs
Codec EntriesBYTE[]VariesArray of codec information structures

 

The Code Entries field is an array of structures. The following table shows the format of each entry:

Codec List Object fieldData typeSizeDescription
TypeDWORD4 bytes

Codec type. This can be one of the following values:

  • 0x0001: Audio codec
  • 0x0002: Video codec
  • 0xFFFF: Unknown
Codec Name LengthDWORD4 bytesSize of the Codec Name string, in bytes, including the NULL character.
Codec NameWCHAR[]VariesNull-terminated Unicode string that contains the name of the codec, such as "Windows Media Video 9".
Codec Description LengthDWORD4 bytesSize of the Codec Description string, in bytes, including the NULL character.
Codec DescriptionWCHAR[]VariesA null-terminated Unicode string that contains a description of the codec.
Codec Information LengthDWORD4 bytesSize of the Codec Information field, in bytes.
Codec InformationBYTE[]VariesCodec data. The meaning of this data depends on the codec. Typically, this data indicates the format.

 

Note  The layout of the attribute blob does not exactly match the layout of the Codec List Object in the ASF header. In particular, string lengths are given in bytes and include the size of the NULL terminator.

Requirements

Minimum supported client

Windows Vista [desktop apps only]

Minimum supported server

Windows Server 2008 [desktop apps only]

Header

Wmcontainer.h

See also

IMFAttributes::GetBlob
IMFAttributes::SetBlob
IMFPresentationDescriptor
Presentation Descriptor Attributes
ASF Header Object
Presentation Descriptors

 

 

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