advanced streaming format (file format) (ASF)

Advanced Streaming Format (ASF) is a container format developed by Microsoft for storing and transferring synchronized multimedia content. With ASF, multimedia data, audio and video from different source information can be compressed and synchronized together. The playback quality is determined by the compression and the selectable compression factor.

ASF can be considered as a universal container for synchronized file formats, in which files with different file formats are combined as a data package.

The ASF file format is organized in objects. Each object is uniquely identified worldwide by the Global User Identifier( GUID) with its 128 bits. There are three object types: the Header Object, the Data Object and the Index Object. The Header Object describes the file content, the Data Object contains the audio and video data that are stored in ASF Data Units, and the Index Object is used for synchronization and contains the timing information for the Data Units.

As with RealAudio, playback starts immediately after the ASF file is called. The ASF specifications are published, unlike the RealAudio specifications. The files can be played using Internet Explorer and Netscape Navigator.

The extension of ASF files is *.asf or for a video file *.wmv.