Windows Media: Advanced Systems Format (.ASF files)
Advanced Systems Format (.ASF files)
Advanced Systems Format (formerly Advanced Streaming Format) is Microsoft's proprietary digital audio/digital video container format, especially meant for streaming media. ASF is part of the Windows Media framework.
The format does not specify how the video or audio should be encoded, but instead just specifies the structure of the video/audio stream. What this means is that .ASF files can be encoded with basically any audio/video codec and still would be in ASF format. This is similar to the function performed by the QuickTime, AVI, or Ogg formats. One of the objectives of the ASF format was to support playback from digital media servers, HTTP servers, and local storage devices.
According to Microsoft, with ASF any object can be placed into an ASF data stream, including audio and video, scripts, ActiveX controls, and HTML documents with T.A.G. Author. This approach, similar to Flash and Shockwave movies, provides less flexibility in terms of updating and serving content, but it offers more stable client-side playback of various media elements and tighter authoring controls.
ASF files have MIME type application/vnd.ms-asf or video/x-ms-asf. (Advanced Stream Redirector .ASX files also have MIME type video/x-ms-asf.)
The ASF format is based on serialized objects which are essentially byte-sequences identified by a GUID marker.
Certain error-correcting techniques related to ASF are patented in the United States (United States Patent 6,041,345 Levi, et al. March 21, 2000) by Microsoft. Although the format is publicly documented by Microsoft, its license limits implementations to closed-source development projects only. Interestingly, Apple's iTunes software now has the capability to convert WMA files to any iTunes supported format.
Inside .ASF files. Extensions of ASF files: .ASF, .WMA, .WMV.
The most common filetypes contained within an ASF file are Windows Media Audio (WMA) and Windows Media Video (WMV). ASF files can also contain objects representing metadata, such as the artist, title, album and genre for an audio track, or the director of a video track, much like the ID3 tags of MP3 files.
Files containing only WMA audio can be named using a .WMA extension, and files of only audio and video content may have the extension .WMV. Both may use the .ASF extension if desired.
ASF and Digital rights management (DRM)
The ASF container provides the framework for digital rights management in Windows Media Audio and Windows Media Video. Janus is the codename for a recent version of Windows Media DRM, which is sometimes used in conjunction with WMA. The DRM technology supports time-limited music such as those offered by unlimited music download services, such as Yahoo! Music Unlimited, Napster and Virgin Digital. Janus DRM is incompatible with most portable audio devices since they typically support up to WMA DRM Version 9. CD tracks ripped with Windows Media Player are "protected" (DRM-restricted) by default, though this setting can be changed.
Some players like ubiquitous Apple iPod do not support DRM protected .WMA files. Besides DRM protected WMA files consume more energy and it means that you can listen to less music on your portable devices. Luckily in many cases it is possible to remove DRM protection using lossy or lossless DRM removal software (DRM remover).
Players supporting Windows Media .ASF files
ASF files are played by players such as MPlayer or Windows Media Player.
Windows Media Player (WMP) 11 is the latest version of Microsoft's media player. You can download Windows Media Player for Windows, Windows Mobile and Mac OS platforms.
Downloading/Recording/Capturing/Ripping/Saving Windows Media video stream
To download/record/capture/rip/save .WMV/.ASF video stream you may use streaming media recorder that supports Windows Media format and the protocol used (RTSP, MMS or HTTP).
WM Recorder is an easy and very powerful stream recorder. It can record Windows Media video streams (.ASF, .WMV) and audio streams (.WMA) streamed through the RTSP, MMS and HTTP protocols. In the PRO and ADA mode WM Recorder can capture packets from Windows Media Player. That is why WM Recorder can capture more Windows Media streams than any other stream recorder.
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