Advanced Systems Format
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Advanced Streaming Format ( ASF or, later renamed the Advanced Systems Format) is a system developed by Microsoft, proprietary container format for digital audio and video that is specifically designed for streaming. ASF is part of the Windows Media framework.
The format does not specify the type of encoding, but only the structure of the audio / video streams. This means that ASF files can be encoded with different codecs, so it is a container format. This is similar to the functionality of the QuickTime, MP4 or Ogg formats.
Construction
The ASF format is based on objects which are essentially byte sequences identified by a GUID and mark.
The most common contents of an ASF file are:
- Windows Media Audio (WMA)
- Windows Media Video ( WMV )
ASF files can also contain objects to represent metadata such as artist, title, album and genre for an audio file, or the director of a film, similar to the ID3 tags of MP3 files.
ASF files containing only WMA audio can with the file extension ". Wma", and files containing only WMA audio and WMV video, be provided with the file extension ". Wmv ". But you can also. " Asf " have as an ending.
ASF is often used to describe Microsoft 's implementation of MPEG -4 ASP video format (Windows Media Video) confused as most ASF streams encoded with this standard.
Patents
The ASF structure ( container, no special codec) is in the U.S. ( United States Patent 6,041,345 Levi, March 21, 2000) patented by Microsoft. Microsoft has made this patent against the free video conversion utility VirtualDub law. The reason for this was the control over the content of ASF files, as only Microsoft programs can play this after the official version. Meanwhile, however, are also free programs such as MPlayer, VLC media player and Xine able to reproduce this container format FFmpeg supports reading and writing of the format. The developers of the programs have not been prosecuted by Microsoft.