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ASF Indexer

The ASF indexer is a WMContainer layer component that is used to read or write Index Objects in an Advanced Systems Format (ASF) file. For information about the structure of an ASF file, see ASF File Structure.

An application can use the indexer to perform seeking based on presentation time or to generate new index entries for an ASF file. The ASF indexer implements the IMFASFIndexer interface.

Index typeDescription
Presentation time-based Index

Provides presentation time-based indexing for audio and video streams in index blocks to make indexing more space efficient. Each index block references index entries that contain a byte offset.

The offset is the position of the data packet being seeked, relative to the start of the ASF Data Object.

GUID_NULL must be used as the GUID type for the index identifier. For more information; see Using the Indexer to Write a New Index.

Timecode Index

Facilitates seeking by timecode in streams which contain timecode metadata. The timecodes conform to a SMPTE format (Hours:Minutes:Seconds:Frames). Each index block references index entries that contain a byte offset.

The offset is the position of the data packet being seeked, relative to the start of the ASF Data Object.

Note   Timecode index objects are not currently supported.

Frame-based Index

Provides frame-based indexing for video streams. Indexes into the frame-based index are in terms of frame numbers, with the first frame for a stream in the ASF file corresponding to entry 0 in the frame-based index object. Each index block references index entries that contain a byte offset.

Note   Frame-based index objects are not currently supported.

 

This section contains the following topics.

TopicDescription
Indexer Creation and Configuration How to create an indexer object and configure it for reading an existing index or for writing a new ASF Index Object for a file.
Using the Indexer to Seek in a File How to use the indexer to seek within an ASF file.
Using the Indexer to Write a New Index How to use the indexer to generate index entries and write a new Index Object for an ASF file.

 

Related topics

ASF Support in Media Foundation

 

 

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