Advanced Systems Format (formerly Advanced Streaming Format, Active Streaming Format) is

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

's proprietary

digital audio Digital audio is a representation of sound recorded in, or converted into, digital signal (signal processing), digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical sampling (signal processing), ...

digital video Digital video is an electronic representation of moving visual images (video) in the form of encoded digital data. This is in contrast to analog video, which represents moving visual images in the form of analog signals. Digital video comprises ...

container format A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Nota ...

, especially meant for

streaming media Streaming media refers to multimedia delivered through a Computer network, network for playback using a Media player (disambiguation), media player. Media is transferred in a ''stream'' of Network packet, packets from a Server (computing), ...

. ASF is part of the Media Foundation framework.

Overview and features

ASF is based on serialized '' objects'' which are essentially

byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable un ...

sequences identified by a

GUID A Universally Unique Identifier (UUID) is a 128-bit label used to uniquely identify objects in computer systems. The term Globally Unique Identifier (GUID) is also used, mostly in Microsoft systems. When generated according to the standard methods ...

marker. The format does not specify how (i.e. with which

codec A codec is a computer hardware or software component that encodes or decodes a data stream or signal. ''Codec'' is a portmanteau of coder/decoder. In electronic communications, an endec is a device that acts as both an encoder and a decoder o ...

) the video or audio should be encoded; it just specifies the structure of the video/audio stream. This is similar to the function performed by the QuickTime File Format, AVI, or

Ogg Ogg is a digital multimedia container format designed to provide for efficient streaming and manipulation of digital multimedia. It is maintained by the Xiph.Org Foundation and is free and open, unrestricted by software patents. Its name is ...

formats. One of the objectives of ASF was to support playback from digital media servers, HTTP servers, and local storage devices such as

hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating hard disk drive platter, pla ...

s. The most common media contained within an ASF file are

Windows Media Audio Windows Media Audio (WMA) is a series of audio codecs and their corresponding audio coding formats developed by Microsoft. It is a proprietary technology that forms part of the Windows Media framework. Audio encoded in WMA is stored in a digi ...

(WMA) and

Windows Media Video Windows Media Video (WMV) is a series of video codecs and their corresponding video coding formats developed by Microsoft. It is part of the Windows Media framework. WMV consists of three distinct codecs: the original video compression technolog ...

(WMV). The most common file extensions for ASF files are extension (audio-only files using Windows Media Audio, with MIME-type audio/x-ms-wma) and (files containing video, using the Windows Media Audio and Video codecs, with MIME-type video/x-ms-asf). These files are identical to the old files but for their extension and MIME-type. The different extensions are used to make it easier to identify the content of a media file. ASF files can also contain objects representing

metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...

, 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 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany under the lead of Karlheinz Brandenburg. It was designed to greatly reduce the amount ...

files. It supports scalable media types and stream prioritization; as such, it is a format optimized for streaming. The ASF container provides the framework for

digital rights management Digital rights management (DRM) is the management of legal access to digital content. Various tools or technological protection measures, such as access control technologies, can restrict the use of proprietary hardware and copyrighted works. DRM ...

in Windows Media Audio and Windows Media Video. An analysis of an older scheme used in WMA reveals that it is using a combination of

elliptic curve cryptography Elliptic-curve cryptography (ECC) is an approach to public-key cryptography based on the algebraic structure of elliptic curves over finite fields. ECC allows smaller keys to provide equivalent security, compared to cryptosystems based on modula ...

key exchange, DES block cipher, a custom block cipher, RC4 stream cipher and the

SHA-1 In cryptography, SHA-1 (Secure Hash Algorithm 1) is a hash function which takes an input and produces a 160-bit (20-byte) hash value known as a message digest – typically rendered as 40 hexadecimal digits. It was designed by the United States ...

hashing function. ASF container-based media are sometimes still streamed on the internet either through the MMS protocol or the RTSP protocol. Mostly, however, they contain material encoded for 'progressive download', which can be distributed by any webserver and then offers the same advantages as streaming: the file starts playing as soon as a minimum number of bytes is received and the rest of the download continues in the background while one is watching or listening. The

Library of Congress The Library of Congress (LOC) is a research library in Washington, D.C., serving as the library and research service for the United States Congress and the ''de facto'' national library of the United States. It also administers Copyright law o ...

Digital Preservation project considers ASF to be the ''de facto'' successor of

RIFF A riff is a short, repeated motif or figure in the melody or accompaniment of a musical composition. Riffs are most often found in rock music, punk, heavy metal music, Latin, funk, and jazz, although classical music is also sometimes based ...

. In 2010

Google Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...

picked RIFF as the container format for

WebP WebP is a raster graphics file format developed by Google intended as a replacement for JPEG, PNG, and GIF file formats. It supports both lossy and lossless compression, as well as animation and alpha transparency. Google announced the WebP ...

License

The specification is downloadable from the Microsoft website, and the format can be implemented under a

license A license (American English) or licence (Commonwealth English) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another part ...

from Microsoft that however does not allow distribution of sources and is not compatible with

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

licenses. The author of the free software project

VirtualDub VirtualDub is a free and open-source video capture and video processing utility for Microsoft Windows written by Avery Lee. It is designed to process linear video streams, including filtering and recompression. It uses AVI container format to s ...

reported that a Microsoft employee informed him that his software violated a Microsoft patent regarding ASF playback. Certain error-correcting techniques related to ASF were patented in the United States
United States Patent 6,041,345
Levi, et al. March 21, 2000) by Microsoft until August 10, 2019.

References

External links

An Overview of Advanced Systems FormatOverview of the ASF FormatLibrary of Congress analysis of ASF format sustainability
* ttp://msdn.microsoft.com/en-us/library/ms983653(loband).aspx MSDN How To Embed Windows Media Player in a HTML Web Page (For Webmasters)br>Creating A Windows Media Custom Experience (For Webmasters)
{{DEFAULTSORT:Advanced System Format Internet Explorer Digital container formats Microsoft Windows multimedia technology Digital rights management systems

Overview and features

License

See also

References

External links