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 audio is a representation of sound In physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy ...

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 compr ...

container format, especially meant for

streaming media Streaming media is multimedia Multimedia is a form of communication that uses a combination of different content forms such as text, audio, images, animations, or video Video is an e ...

. ASF is part of the Media Foundation framework.

Overview and features

ASF is based on serialized ''

objects Object may refer to: General meanings * Object (philosophy) An object is a philosophical term often used in contrast to the term '' subject''. A subject is an observer and an object is a thing observed. For modern philosophers like Descarte ...

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

codec A codec is a device or computer program A computer program is a sequence or set of instructions in a programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-b ...

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

HTTP server An HTTP server is a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of oper ...

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 hard disk platter, platters ...

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

Windows Media Audio Windows Media Audio (WMA) is a series of audio codec An audio codec is a device or computer program capable of encoding or decoding a digital data stream (a codec A codec is a device or computer program A computer program is a sequence or ...

(WMA) and Windows Media Video (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 is " data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the 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 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 wor ...

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 Public-key cryptography, or asymmetric cryptography, is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key an ...

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

SHA-1 In cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia ''-logy'' is a suffix in the English language, used with words originally adapted from Ancie ...

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 In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple anal ...

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 Research is " creative and systematic work undertaken to increase the stock of knowledge Knowledge can be defined as awareness of facts or as practical skills, and may also ref ...

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

RIFF A riff is a repeated chord progression or refrain in music Music is generally defined as the art of arranging sound to create some combination of form, harmony, melody, rhythm or otherwise expressive content. Exact definiti ...

. In 2010

Google Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing Cloud computing is the on-demand availability of computer system resources, especially dat ...

picked RIFF as the container format for

WebP WebP is an image file format An Image file format is a file format for a digital image. There are many formats that can be used, such as JPEG, PNG, and GIF. Most formats up until 2022 were for storing 2D images, not 3D ones. The data st ...

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 In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language A programming language is a system of notation for writin ...

licenses. The author of the free software project VirtualDub 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