Advanced Streaming Format

Advanced Streaming Format (or ASF, later renamed into Advanced Systems Format) is Microsoft's proprietary digital audio/digital video container format, especially meant for streaming media. ASF is part of the Windows Media framework.

Related Topics:
Microsoft - Proprietary - Digital audio - Digital video - Container format - Streaming media - Windows Media

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

Related Topics:
Encode - Codec - QuickTime - AVI - Ogg

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The ASF format is based on serialized objects which are essentially byte-sequences identified by a GUID marker.

Related Topics:
Serialized - Byte - GUID

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The most common filetypes contained within an ASF file are Windows Media Audio (WMA) and Windows Media Video (WMV).

Related Topics:
Windows Media Audio - Windows Media Video

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

Related Topics:
Metadata - ID3 - MP3

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The format is often confused with Microsoft's own implementation of MPEG-4 video format (Windows Media Video), because most ASF streams are encoded using this codec.

Related Topics:
MPEG-4 - Windows Media Video

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The ASF container structure is patented in the United States (United States Patent 6,041,345 Levi, et al. March 21, 2000) by Microsoft. They have invoked this patent against VirtualDub, a free video conversion program. Interestingly, Apple's iTunes software now has the capability to convert WMA files to AAC http://www.apple.com/itunes/import.html.

Related Topics:
VirtualDub - Apple - ITunes

~ ~ ~ ~ ~ ~ ~ ~ ~ ~