Advanced Systems Format

This image illustrates the computer icons that Windows Vista displays for Advanced Systems Format, depending on the file name extension. From left to right, the icons correspond to .asf, .wma, and .wmv files.

Filename extension| `.asf .wma .wmv`
Type code| 'ASF_'
Uniform Type Identifier (UTI)| com.microsoft.advanced-systems-format
Magic number| 30 26 B2 75 8E 66 CF 11 A6 D9 00 AA 00 62 CE 6C[1]
Developed by| Microsoft
Initial release| Proprietary: 16 September 1996; 29 years ago (1996-09-16)[2][3]
Public: 26 February 1998; 28 years ago (1998-02-26)[4]
Latest release|

01.20.03
(December 2004; 21 years ago (2004-12))

Type of format| Container format
Container for| Windows Media Audio, Windows Media Video, VC-1
Open format?| No[5]

Advanced Systems Format (formerly Advanced Streaming Format, Active Streaming Format) is Microsoft's proprietary digital audio/digital video container format, especially meant for streaming media. ASF is part of the Media Foundation framework.

## Contents

* 1 Overview and features
* 2 License
* 3 See also
* 4 References
* 5 External links

## Overview and features

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

The format does not specify how (i.e. with which codec) 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 servers, and local storage devices such as hard disk drives.

The most common media contained within an ASF file are Windows Media Audio (WMA) and Windows Media Video (WMV). The most common file extensions for ASF files are extension .WMA (audio-only files using Windows Media Audio, with MIME-type `audio/x-ms-wma`) and .WMV (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 .ASF 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.[6]

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. 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 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 key exchange, DES block cipher, a custom block cipher, RC4 stream cipher and the SHA-1 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 Digital Preservation project considers ASF to be the de facto successor of RIFF.[1] In 2010 Google picked RIFF as the container format for WebP.

## License

The specification is downloadable from the Microsoft website,[7] and the format can be implemented under a license from Microsoft that however does not allow distribution of sources and is not compatible with open source 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.[8]

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.

## See also

* Audio Video Interleave (AVI)
* Comparison of container formats

## References

1. ↑ 1.0 1.1 "ASF (Advanced Systems Format)". Digital Preservation. Library of Congress. 2014-02-04. http://www.digitalpreservation.gov/formats/fdd/fdd000067.shtml.
2. ↑ "Advanced Streaming Format". https://www.tech-insider.org/digital-video/research/1997/asf/index.htm.
3. ↑ "Microsoft Introduces NetShow, A Platform for Delivering Multimedia Content Over Intranets". 1996-09-16. https://news.microsoft.com/1996/09/16/microsoft-introduces-netshow-a-platform-for-delivering-multimedia-content-over-intranets/.
4. ↑ Fleischman, Eric (26 February 1998), Advanced Streaming Format (ASF) Specification, Internet Engineering Task Force, I-D draft-fleischman-asf-01, https://tools.ietf.org/html/draft-fleischman-asf-01, retrieved 13 December 2021
5. ↑ ASF (Advanced Systems Format) (Full draft). Sustainability of Digital Formats. Washington, D.C.: Library of Congress. 6 April 2007. Retrieved 1 December 2021.
6. ↑ "The Difference Between ASF and WMV/WMA Files". http://support.microsoft.com/kb/284094.
7. ↑ "ASF Specification Download". http://download.microsoft.com/download/7/9/0/790fecaa-f64a-4a5e-a430-0bccdab3f1b4/ASF_Specification.doc.
8. ↑ Advogato: Microsoft patents ASF media file format, stops reverse engineering, http://www.advogato.org/article/101.html, retrieved 2019-03-11

## External links

* An Overview of Advanced Systems Format
* Overview of the ASF Format
* Library of Congress analysis of ASF format sustainability
* ASF Container Format - v2.0 (free available but unused) and v1.0 (reconstructed)
* MSDN How To Embed Windows Media Player in a HTML Web Page (For Webmasters)
* Creating A Windows Media Custom Experience (For Webmasters)

* v
* t
* e

Multimedia compression and container formats

Video
compression|

| ISO, IEC, MPEG|

* MJPEG
* Motion JPEG 2000
* MPEG-1
* MPEG-2
* Part 2
* MPEG-4
* Part 2 / ASP
* Part 10 / AVC
* MPEG-H
* Part 2 / HEVC
* MPEG-I
* Part 3 / VVC

|

ITU-T, VCEG|

* H.120
* DCT
* H.261
* H.262
* H.263
* H.264 / AVC
* H.265 / HEVC
* H.266 / VVC
* DV

SMPTE|

* VC-1
* VC-2
* VC-3
* VC-5

TrueMotion|

* TrueMotion S
* DCT
* VP3
* VP6
* VP7
* VP8
* VP9
* AV1

Others|

* Apple Video
* AVS
* Bink
* Cinepak
* Daala
* DVI
* EVC
* FFV1
* Huffyuv
* Indeo
* Lagarith
* Microsoft Video 1
* MSU Lossless
* OMS Video
* Pixlet
* ProRes 422
* ProRes 4444
* QuickTime
* Animation
* Graphics
* RealVideo
* RTVideo
* SheerVideo
* Smacker
* Sorenson Video/Spark
* Theora
* Thor
* WMV
* XEB
* YULS

Audio
compression|

| ISO, IEC, MPEG|

* MPEG-1 Layer II
* Multichannel
* MPEG-1 Layer I
* MPEG-1 Layer III (MP3)
* AAC
* HE-AAC
* AAC-LD
* MPEG Surround
* MPEG-4 ALS
* MPEG-4 SLS
* MPEG-4 DST
* MPEG-4 HVXC
* MPEG-4 CELP
* MPEG-D USAC
* MPEG-H 3D Audio

|

ITU-T|

* G.711
* A-law
* µ-law
* G.718
* G.719
* G.722
* G.722.1
* G.722.2
* G.723
* G.723.1
* G.726
* G.728
* G.729
* G.729.1

IETF|

* Opus
* iLBC
* Speex
* Vorbis

3GPP|

* AMR
* AMR-WB
* AMR-WB+
* EVRC
* EVRC-B
* EVS
* GSM-HR
* GSM-FR
* GSM-EFR

ETSI|

* AC-3
* AC-4
* DTS

Others|

* ACELP
* ALAC
* Asao
* ATRAC
* AVS
* CELT
* Codec 2
* DRA
* FLAC
* iSAC
* Monkey's Audio
* TTA
* True Audio
* MT9
* Musepack
* OptimFROG
* OSQ
* QCELP
* RCELP
* RealAudio
* RTAudio
* SD2
* SHN
* SILK
* Siren
* SMV
* SVOPC
* TwinVQ
* VMR-WB
* VSELP
* WavPack
* WMA
* MQA
* aptX
* aptX HD
* aptX Low Latency
* aptX Adaptive
* LDAC
* LHDC
* LLAC

Image
compression|

| IEC, ISO,
IETF, W3C,
ITU-T, JPEG|

* CCITT Group 4
* DCT
* HEIF
* HEVC
* JPEG
* JPEG XR
* JPEG XT
* TIFF/EP
* Arithmetic
* JBIG
* JBIG2
* JPEG-LS
* JPEG 2000
* LZ
* GIF
* PNG
* TIFF
* TIFF/IT

|

Others|

* APNG
* BPG
* DjVu
* EXR
* FLIF
* ICER
* MNG
* PGF
* QTVR
* WBMP
* WebP

Containers|

| ISO, IEC|

* MPEG-ES
* MPEG-PES
* MPEG-PS
* MPEG-TS
* ISO base media file format
* MPEG-4 Part 14 (MP4)
* Motion JPEG 2000
* MPEG-21 Part 9
* MPEG media transport

|

ITU-T|

* H.222.0
* T.802

IETF|

* RTP
* Ogg

SMPTE|

* GXF
* MXF

Others|

* 3GP and 3G2
* AMV
* ASF
* AIFF
* AVI
* AU
* BPG
* Bink
* Smacker
* BMP
* DivX Media Format
* EVO
* Flash Video
* IFF
* M2TS
* Matroska
* WebM
* QuickTime File Format
* RatDVD
* RealMedia
* RIFF
* WAV
* MOD and TOD
* VOB, IFO and BUP

Collaborations|

* NETVC
* MPEG LA
* HEVC Advance

Methods|

* Discrete cosine transform
* DCT
* MDCT
* Entropy
* Arithmetic
* Huffman
* Modified
* FFT
* LPC
* ACELP
* CELP
* LSP
* WLPC
* Lossless
* Lossy
* LZ
* DEFLATE
* LZW
* PCM
* A-law
* µ-law
* ADPCM
* DPCM
* Transform
* Wavelet
* Daubechies
* DWT
* Transform

Lists|

* Comparison of audio coding formats
* Comparison of video codecs
* List of codecs

See Compression methods for techniques and Compression software for codecs

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