Advanced streaming format
| Advanced streaming format | |
|---|---|
| File extension : |
.asf
|
| MIME type : | video / x-ms-asf, application / vnd.ms-asf |
| Magic number : | 30 26 b2 75 |
| Developed by: | Microsoft |
| Type: | Container format |
| Container for: |
Audio , video , text codecs: WMA , WMV , ... |
| Website : | Microsoft ASF Specification |
Advanced Streaming Format (or ASF , later renamed Advanced Systems Format ) is a proprietary container format for digital audio and video developed by Microsoft that is specifically designed for streaming . ASF is part of the Windows Media Framework .
The format does not determine the type of encoding, only the structure of the audio / video stream. This means that ASF files can be encoded with different codecs , so it is a container format. This is comparable to the functionality of the QuickTime , MP4 or Ogg formats.
construction
The ASF format is based on objects whose byte sequences are recognized by means of a GUID marking.
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 movie, similar to the ID3 tags of MP3 files.
ASF files that only contain WMA audio can have the file extension ".wma", and files that only contain WMA audio and WMV video can have the file extension ".wmv". But they can also have ".asf" as the ending.
ASF is often confused with Microsoft's own implementation of the MPEG-4 Windows Media Video ( ASP ) video format , as most ASF streams have been encoded using this standard.
Patents
The ASF structure (the container, not a special codec) is patented by Microsoft in the United States (United States Patent 6,041,345 Levi, March 21, 2000). Microsoft has asserted this patent against the free video conversion program VirtualDub . The reason for this was the control over the contents of ASF files, since only programs from Microsoft can reproduce them according to the official reading. In the meantime, however, free programs such as MPlayer , VLC media player (partially restricted) and Xine can also play this container format, FFmpeg supports reading and writing. The developers of the programs have not yet been prosecuted by Microsoft.