ASF: Advanced Systems Format

ASF stands for Advanced Systems Format, it's Microsoft's proprietary digital audio/digital video container format, especially meant for streaming media. The most common file types contained within an ASF file are Windows Media Audio (WMA) and Windows Media Video (WMV). Note that the file extension abbreviations are different from the codecs which have the same name. When an ASF file is played back, content is delivered to you as a continuous flow of data. You no longer have to wait for the whole video and audio file fully download before you start to view them. As a result, this file format is specially designed to run on networks.

Advanced Streaming Format is an open file format specification for streaming multimedia files containing text, graphics, sound, video, and animation. Advanced Streaming Format (ASF) does not define the format for any media streams within the file. Rather, it defines a standardized, extensible file container that is not dependent on a particular operating system or communication protocol, or on a particular method (such as HTML or MPEG 4) used to compose the data stream in the file. An ASF file consists of three objects: a Header object containing information about the file itself, a Data object containing the media streams, and an optional Index object that can help support random access to data within the file. The ASF specification has been submitted to the ISO (International Organization for Standardization) for consideration. A number of programs capture this file extension.

How to play .ASF files on Mac OS X?

A solution is VLC. It plays a wide variety of video formats, including VCDs and DVDs.

Another solution is MPlayer, which plays a wide variety of formats. It's still under development and has some rough edges, so at this point VLC is a better choice.

VLC media player (also known as VLC) is a highly portable free and open-source media player and streaming media server written by the VideoLAN project. It is a cross-platform media player, with versions for Microsoft Windows, Mac OS X, Linux, BeOS, MorphOS, BSD, Solaris, iOS, and eComStation.

VLC media player supports many audio and video compression methods and file formats, including DVD-video, video CD and streaming protocols. It is able to stream over computer network and to transcode multimedia files.