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

Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation producing Software, computer software, consumer electronics, personal computers, and related services headquartered at th ...

's proprietary digital audio/ digital video

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. Not ...

, especially meant for

streaming media Streaming media is multimedia that is delivered and consumed in a continuous manner from a source, with little or no intermediate storage in network elements. ''Streaming'' refers to the delivery method of content, rather than the content i ...

. ASF is part of the

Media Foundation Media Foundation (MF) is a COM-based multimedia framework pipeline and infrastructure platform for digital media in Windows Vista, Windows 7, Windows 8, Windows 8.1, Windows 10, and Windows 11. It is the intended replacement for Microsoft Direc ...

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 unit ...

sequences identified by a

GUID A universally unique identifier (UUID) is a 128-bit label used for information in computer systems. The term globally unique identifier (GUID) is also used. When generated according to the standard methods, UUIDs are, for practical purposes, uni ...

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

codec A codec is a device or computer program 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 on a signal or ...

) 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 QuickTime File Format (QTFF) is a computer file format used natively by the QuickTime framework. Design The format specifies a multimedia container file that contains one or more tracks, each of which stores a particular type of data: audio, ...

, AVI, or

Ogg Ogg is a free, open container format maintained by the Xiph.Org Foundation. The authors of the Ogg format state that it is unrestricted by software patents and is designed to provide for efficient streaming and manipulation of high-quality di ...

formats. One of the objectives of ASF was to support playback from digital media servers,

HTTP server An HTTP server is a computer (software) program (or even a software component included in an other program) that plays the role of a server in a client–server model by implementing the ''server part'' of the HTTP and/or HTTPS network proto ...

s, 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 platters coated with magn ...

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. WMA consists of four distinct codecs. The ...

(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 technology ...

(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, such as the artist, title, album and genre for an audio track, or the director of a video track, much like the

ID3 ID3 is a metadata container most often used in conjunction with the MP3 audio file format. It allows information such as the title, artist, album, track number, and other information about the file to be stored in the file itself. There are tw ...

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, with support from other digital scientists in the United States and elsewhere. Orig ...

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 (TPM) such as access control technologies can restrict the use of proprietary hardware and copyrighted work ...

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 compared to non-EC cryptography (based on plain Galois fields) to provide e ...

key exchange, DES block cipher, a custom block cipher,

RC4 In cryptography, RC4 (Rivest Cipher 4, also known as ARC4 or ARCFOUR, meaning Alleged RC4, see below) is a stream cipher. While it is remarkable for its simplicity and speed in software, multiple vulnerabilities have been discovered in RC4, ren ...

stream cipher and the

SHA-1 In cryptography, SHA-1 (Secure Hash Algorithm 1) is a cryptographically broken but still widely used hash function which takes an input and produces a 160-bit (20- byte) hash value known as a message digest – typically rendered as 40 hexadec ...

hashing function. ASF container-based media are sometimes still streamed on the internet either through the MMS protocol or the

RTSP The Real Time Streaming Protocol (RTSP) is an application-level network protocol designed for multiplexing and packetizing multimedia transport streams (such as interactive media, video and audio) over a suitable transport protocol. RTSP is u ...

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 the research library that officially serves the United States Congress and is the ''de facto'' national library of the United States. It is the oldest federal cultural institution in the country. The librar ...

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

RIFF A riff is a repeated chord progression or refrain in music (also known as an ostinato figure in classical music); it is a pattern, or melody, often played by the rhythm section instruments or solo instrument, that forms the basis or accompanim ...

. In 2010

Google Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...

picked RIFF as the container format for

WebP WebP is an image 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 format ...

License

The specification is downloadable from the Microsoft website,ASF Specification Download
/ref> and the format can be implemented under a

license A license (or licence) 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 party (licensee) as an element of an agreeme ...

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 the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

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 t ...

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 2019-08-10.

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