View source for VC-1

{{Short description|Video coding format developed by Microsoft}}
{{Other uses|VC1 (disambiguation){{!}}VC1}}
{{distinguish|AVC1|AV1}}
{{Infobox file format
| name = VC-1
| icon = 
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| caption = 
| noextcode = 
| nomimecode = 
| mime = 
| type code = 
| uniform_type = 
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| developer = [[Society of Motion Picture and Television Engineers|SMPTE]], [[Microsoft]], [[Panasonic]], [[LG Electronics|LG]], [[Samsung Electronics|Samsung]], [[#Patent holders|etc.]]
| released = {{start date and age|2006|02|24|df=y}}
| latest_release_version = SMPTE ST 421:2013
| latest_release_date = {{start date and age|2013|10|08|df=y}}
| type = [[Video coding format]]
| contained_by = 
| extended_from = [[Windows Media Video|WMV 9]]
| extended_to = 
| standards = SMPTE ST 421
| open = Yes
| free = No<ref>{{cite tech report |publisher=Library of Congress |location=Washington, D.C. |series=Sustainability of Digital Formats |type=Full draft |title=Windows Media 9 Video Codec; SMPTE VC-1 |date=26 May 2010 |url=https://www.loc.gov/preservation/digital/formats/fdd/fdd000081.shtml |access-date=13 December 2021}}</ref>
| url = {{#statements:official website}}
}}
'''SMPTE 421''',<ref>{{Cite journal |date=October 2013 |title=ST 421:2013 - SMPTE Standard - VC-1 Compressed Video Bitstream Format and Decoding Process |url=https://ieeexplore.ieee.org/document/7290900 |archive-url=https://web.archive.org/web/20180606164955/https://ieeexplore.ieee.org/document/7290900/ |url-status=dead |archive-date=June 6, 2018 |journal=St 421:2013 |pages=i–493 |doi=10.5594/SMPTE.ST421.2013|isbn=978-1-61482-770-2 |url-access=subscription }}</ref> informally known as '''VC-1''', is a [[video coding format]]. Most of it was initially developed as [[Microsoft]]'s proprietary video format [[Windows Media Video|Windows Media Video 9]] in 2003. With some enhancements including the development of a new Advanced Profile, it was officially approved as an [[Society of Motion Picture and Television Engineers|SMPTE]] standard on April 3, 2006. It was primarily marketed as a lower-complexity competitor to the [[H.264/MPEG-4 AVC]] standard. After its development, several companies other than Microsoft asserted that they held [[patent]]s that applied to the technology, including [[Panasonic]], [[LG Electronics]] and [[Samsung Electronics]].

VC-1 is supported in the now-deprecated [[Microsoft Silverlight]], the briefly-offered [[HD DVD]] disc format, and the [[Blu-ray Disc]] format.

==Format==
VC-1 is an evolution of the conventional block-based [[motion compensation|motion-compensated]] hybrid video coding design also found in [[H.261]], [[MPEG-1#Part 2: Video|MPEG-1 Part 2]], [[H.262/MPEG-2 Part 2]], [[H.263]], and [[MPEG-4 Part 2]]. It was widely characterized as an alternative to the [[ITU-T]] and [[MPEG]] video codec standard known as [[H.264/MPEG-4 AVC]]. The Advanced Profile of VC-1 contains tools designed for coding [[Interlaced video|interlaced]] video sequences as well as [[progressive scan]] video. The main goal of the development and standardization of the VC-1 Advanced Profile was to support interlace-optimized compression of interlaced content without first converting it to progressive scan, making it more attractive to broadcast and video industry professionals using the [[1080i]] format.

Both [[HD DVD]] and [[Blu-ray Disc]] adopted VC-1 as a supported video format, meaning their video playback devices are required to be capable of decoding and playing video-content compressed using VC-1. [[Windows Vista]] partially supports HD DVD playback by including the VC-1 decoder and some related components needed for playback of VC-1 encoded HD DVD movies.<ref name = "MicrosoftVC1">{{Cite web | year = 2006 | work = Windows Media | url = http://www.microsoft.com/windows/windowsmedia/howto/articles/vc1techoverview.aspx | title = VC-1 Technical Overview | publisher = Microsoft | access-date = October 5, 2006 }}</ref>

Microsoft designated VC-1 as the [[Xbox 360]] [[video game console]]'s official video format, and game developers could use VC-1 for [[full motion video]] included with games. By means of an October 31, 2006 update, all formats of Windows Media Video could be played on the Xbox 360 from a disc, USB storage device, or streaming from a PC via Windows Media Connect/Windows Media Player 11.

VC-1 is supported in the [[PlayStation 3]] console and the [[FFmpeg]] project also includes a VC-1 decoder.<ref name= "FFmpeg VC-1 Google 2006 SoC">{{cite web| url= http://code.google.com/soc/2006/ffmpeg/about.html | title= VC-1 | work = Summer of Code| access-date = 2007-03-21 | archive-url = https://web.archive.org/web/20070913044216/http://code.google.com/soc/2006/ffmpeg/appinfo.html?csaid=5AA777DB19E2BB24 | archive-date = 2007-09-13}}</ref>

On August 24, 2012, the [[Raspberry Pi]] Foundation announced hardware decoding support for VC-1.<ref name = "Raspberry Pi VC-1 Support">{{cite web | year = 2012 | url = http://www.raspberrypi.org/archives/1839 | title = Raspberry Pi VC-1 Hardware Decoding | publisher = Raspberry Pi Foundation | access-date = August 24, 2012 | archive-date = October 4, 2013 | archive-url = https://web.archive.org/web/20131004233225/http://www.raspberrypi.org/archives/1839 | url-status = dead }}</ref>

==Microsoft codec implementations==
The VC-1 codec specification has so far been implemented by Microsoft in the form of three codecs, each identified with a unique [[FourCC|four character code]].<ref>{{cite web|last=Sullivan|first=Gary J.|title=DirectX Video Acceleration Specification for Windows Media Video v8, v9 and vA Decoding (Including SMPTE 421M "VC-1")|url=http://download.microsoft.com/download/5/d/c/5dc91455-0a8c-4d57-8975-0afe1cfaf0dd/DXVA_WMV.pdf|work=Microsoft Developer Network (MSDN) Library, Windows Development Kit, Windows Driver Kit, Device and Driver Technologies, Display Devices (Adapters and Monitors), Design Guide, Windows 2000 Display Driver Model Design Guide|publisher=[[Microsoft]]|access-date=29 October 2010|orig-year=December 2007|date=August 2010}}</ref>

===WMV3===
The Simple and Main Profiles of VC-1 remained completely faithful to the existing WMV3 implementation, making WMV3 bitstreams fully VC-1 compliant.
The WMV3 codec was designed to primarily support progressive encoding for computer displays. An interlaced encoding mode was implemented, but quickly became deprecated when Microsoft started implementing WMV Advanced Profile. Whereas WMV3 progressive encoding was implemented using the [[YUV 4:2:0]] color sampling scheme, the deprecated interlaced mode was implemented using the less common [[YUV 4:1:1]] sampling scheme.

The [[Windows Media Video]] 9 (WMV3) codec implements the Simple and Main modes of the VC-1 codec standard, providing high-quality video for streaming and downloading. "It provides support for a wide range of bit rates, from high-definition content at one-half to one-third the bit rate of MPEG-2, to low-bit-rate Internet video delivered over a dial-up modem. This codec also supports professional-quality downloadable video with two-pass and variable bit rate (VBR) encoding."<ref name=MSDN-WMC>{{cite web|title=About the Windows Media Codecs|url=http://msdn.microsoft.com/en-us/library/windows/desktop/gg153556(v=vs.85).aspx|work=Microsoft Developer Network|publisher=Microsoft|access-date=28 April 2014}}</ref>

===WMVA===
WMVA was the original implementation of WMV Advanced Profile prior to the acceptance of the VC-1 draft by SMPTE. The codec was distributed with [[Windows Media Player]] 10 and Windows Media Format SDK 9.5 install packages. There are slight bitstream differences between WMVA and WVC1, so consequently WMVA is handled by a different [[DirectShow]] decoder than WVC1. Some 3rd party hardware and software decoders only decode WMVA based content. As of 2006, WMVA is considered a deprecated codec because it is not fully VC-1 compliant.

===WVC1===
WVC1 (renamed by Microsoft to Windows Media Video 9) offers support for interlaced content and is transport independent. With the previous version of the Windows Media Video 9 Series codec, users could deliver progressive content at data rates as low as one-third that of the MPEG-2 codec and still get equivalent or comparable quality to MPEG-2{{Citation needed|date=February 2010}}. The Windows Media Video 9 Advanced Profile codec also offers this same improvement in encoding efficiency with interlaced contents{{Citation needed|date=February 2010}}. A decoder for WVC1 is included in [[Windows Media Player|Windows Media Player 11]], which is bundled with Windows Vista and is available as a download for Windows XP. This implementation is supported in [[Microsoft Silverlight]].

==Profiles==
{| class="wikitable" style="margin:1em auto; font-size: 100%; text-align: center;"
|-
!
!Simple
!Main
!Advanced
|-
! Baseline intra frame compression
| {{yes}}
| {{yes}}
| {{yes}}
|-
! Variable-sized transform
| {{yes}}
| {{yes}}
| {{yes}}
|-
! 16-bit transform
| {{yes}}
| {{yes}}
| {{yes}}
|-
! Overlapped transform
| {{yes}}
| {{yes}}
| {{yes}}
|-
! 4 motion vector per macroblock
| {{yes}}
| {{yes}}
| {{yes}}
|-
! {{frac|1|4}} pixel luminance motion compensation
| {{yes}}
| {{yes}}
| {{yes}}
|-
! {{frac|1|4}} pixel chrominance motion compensation
| {{no}}
| {{yes}}
| {{yes}}
|-
! Start codes
| {{no}}
| {{yes}}
| {{yes}}
|-
! Extended motion vectors
| {{no}}
| {{yes}}
| {{yes}}
|-
! Loop filter
| {{no}}
| {{yes}}
| {{yes}}
|-
! Dynamic resolution change
| {{no}}
| {{yes}}
| {{yes}}
|-
! Adaptive macroblock quantisation
| {{no}}
| {{yes}}
| {{yes}}
|-
! [[B frames]]
| {{no}}
| {{yes}}
| {{yes}}
|-
! Intensity compensation
| {{no}}
| {{yes}}
| {{yes}}
|-
! Range adjustment
| {{no}}
| {{yes}}
| {{yes}}
|-
! Field and frame coding modes
| {{no}}
| {{no}}
| {{yes}}
|-
! [[Group of pictures|GOP]] Layer
| {{no}}
| {{no}}
| {{yes}}
|-
! Display metadata
| {{no}}
| {{no}}
| {{yes}}
|-
!
!Simple
!Main
!Advanced
|}

==Bit rates and resolutions==
{| class="wikitable" style="margin:1em auto;"
|- style="text-align: center;"
! Profile
! Level
! Maximum [[Bit rate|Bit Rate]]
! Resolution / Framerate
|- style="background:#f9f9f9;"
|rowspan=2| '''Simple'''
| Low
| 96 kbit/s
| 176 × 144 / 15 ([[Common Intermediate Format|QCIF]])
|- style="background:#f9f9f9;"
| Medium
| 384 kbit/s
| 240 × 176 / 30<br>352 × 288 / 15 ([[Common Intermediate Format|CIF]])
|- style="background:#efefef;"
|rowspan=3| '''Main'''
| Low
| 2 Mbit/s
| 320 × 240 / 24 ([[QVGA]])
|- style="background:#efefef;"
| Medium
| 10 Mbit/s
| 720 × 480 / 30 (480p)<br>720 × 576 / 25 (576p)
|- style="background:#efefef;"
| High
| 20 Mbit/s
| 1920 × 1080 / 30 (1080p)
|- style="background:#f9f9f9;"
|rowspan=5| '''Advanced'''
| L0
| 2 Mbit/s
| 352 × 288 / 30 (CIF)
|- style="background:#f9f9f9;"
| L1
| 10 Mbit/s
| 720 × 480 / 30 (NTSC-SD)<br>720 × 576 / 25 (PAL-SD)
|- style="background:#f9f9f9;"
| L2
| 20 Mbit/s
| 720 × 480 / 60 (480p)<br>1280 × 720 / 30 (720p)
|- style="background:#f9f9f9;"
| L3
| 45 Mbit/s
| 1920 × 1080 / 24 (1080p)<br>1920 × 1080 / 30 (1080i)<br>1280 × 720 / 60 (720p)
|- style="background:#f9f9f9;"
| L4
| 135 Mbit/s
| 1920 × 1080 / 60 (1080p)<br>2048 × 1536 / 24<br>2048 × 2048 / 30
|}

==Other implementations==
There are no external implementations of WMV9/AV-1 encoders. For example, Sonic Cinevision PSE- a VC-1 encoding tool, has ben written entirely by Microsoft itself.  Microsoft owns the code and [[Sonic Solutions]] was tasks with sales. Microsoft on it's own (without relying on Sonic company) also provides a separate VC-1 Encoder SDK which allows any company or software developer to integrate VC-1 encoding into their applications.
Non-Microsoft VC-1 implementations (based entirely on the SMPTE specifications) have been done by [[Ericsson Television]] and [[MainConcept]].<ref>{{cite web | title = MainConcept VC-1 Codec Package | publisher = [[MainConcept]]| url = http://www.mainconcept.com/products/sdks/video/vc-1.html | access-date = September 24, 2010}}</ref> The [[FFmpeg]] project includes a [[free software|free]] VC-1 decoder.<ref name="FFmpeg VC-1 Google 2006 SoC"/><ref>{{cite web|url=http://www.ffmpeg.org/|title=FFmpeg Home/News|publisher=FFmpeg|access-date=29 October 2010|date=March 9, 2007|quote=Nine months without news but with heavy development. A few select highlights are decoders for VC-1/WMV3/WMV9, VMware, VP5, VP6 video and WavPack, IMC, DCA audio and a WMA encoder.}}</ref>

==Encoding software==
[[Windows Media Encoder]] 9 Series encodes VC-1 compliant video files, including WVC1 [[FourCC]] media. Windows Media Format 11 Runtime or Windows Media Player 11 must be installed on the computer to ensure full VC-1 compliance across all three profiles (Simple, Main and Advanced). If either of these are installed, [[Windows Movie Maker]] can also save VC-1 compliant videos, as can any other application built on the Windows Media Format SDK or Windows Media Codec DMOs. A Windows Media Encoder Studio Edition was initially announced for professional encoding but later cancelled by Microsoft. [[Microsoft Expression Encoder]] which is part of [[Microsoft Expression Studio|Expression Studio]] supports encoding VC-1 video to the Windows Media ([[Advanced Systems Format|ASF]]) file format and the [[Adaptive bitrate streaming#Microsoft Smooth Streaming|IIS Smooth Streaming]] format.

Video encoder products made by Inlet, [[Digital Rapids Corporation|Digital Rapids]], [[Harmonic Inc.|Harmonic]], Envivio, [[Elemental Technologies]], [[Anystream]], [[Telestream]] and Rhozet support VC-1 encoding (based on the Microsoft VC-1 Encoder SDK) for IPTV and Web streaming.

== Hardware-based encoding and decoding ==

Because VC-1 encoding and decoding requires significant computing power, software implementation that run on a general-purpose CPU are typically slow, especially when dealing with [[High-definition television|HD]] video content. To reduce CPU usage or to do real-time encoding, special-purpose hardware may be employed, either for the complete encoding or decoding process, or for acceleration assistance within a CPU-controlled environment. A hardware VC-1 encoder can be an [[Application-specific integrated circuit|ASIC]] or an [[FPGA]].

Hardware-accelerated (also known as hardware-assisted) video decoding can either be done on dedicated, special-purpose hardware or on generic, multi-purpose hardware such as [[GPU]]s. The former is typically found in consumer electronics devices such as [[Blu-ray Disc]] players and 3G/4G mobile phones, while the latter is typically found in PCs. Nearly all video cards manufactured since 2006 support some level of GPU-accelerated VC-1 decoding on the Windows platform via [[DirectX Video Acceleration]] APIs. The native Windows WMV9/VC-1 decoder (wmvdecod.dll) only supports DXVA profiles A, B and C, while 3rd party VC-1 decoders such as [[CyberLink]]'s support the full DXVA Profile D decode acceleration. There is no support for GPU-accelerated VC-1 decode on the MacOS platform.

[[Raspberry Pi]] hardware prior to Raspberry Pi 4 supports VC-1 hardware-accelerated decoding, although it requires purchasing of a license key.<ref>{{Cite web|title = New video features! MPEG-2 and VC-1 decode, H.264 encode, CEC support|url = https://www.raspberrypi.org/blog/new-video-features/|website = Raspberry Pi| date=24 August 2012 |access-date = 2015-11-29}}</ref>

== Legal status ==
Although heavily associated with [[Microsoft]], there are 18 member companies within the VC-1 [[patent pool]].<ref name="VC1PatentList">{{cite news |title=VC-1 Licensors |url=https://www.via-la.com/licensing-2/vc-1/vc-1-patent-list/ |access-date=2025-07-31 |publisher=[[Via-LA]]}}</ref> The majority of patents are held by four companies: Microsoft (324 patents), [[Panasonic]] (122 patents), [[LG Electronics]] (96 patents), and [[Samsung Electronics]] (96 patents).

As an SMPTE standard, VC-1 is open to implementation by anyone, although implementers may be required to pay licensing fees to the [[Via-LA]], the LLC licensing body or directly to its members, who claim to hold [[essential patent]]s on the format (since it is a non-exclusive licensing body).<ref>{{Cite web | url = http://www.mpegla.com/news/n_06-08-17_pr.pdf | title = MPEG LA, LLC. Press Release| access-date = August 17, 2006 |archive-url = https://web.archive.org/web/20061113145526/http://www.mpegla.com/news/n_06-08-17_pr.pdf <!-- Bot retrieved archive --> |archive-date = November 13, 2006}}</ref>

Over 94.7% of the patents have expired as of July 31, 2025.<ref name=VC1PatentList />

=== Patent holders ===
{{Transcluded section|Via-LA}}

The following organizations hold one or more patents in the VC-1 patent pool, as listed by [[Via-LA]].

{{#section-h:Via-LA|VC-1 licensors}}

==See also==
*[[AV1]]
*[[Comparison of H.264 and VC-1]]
*[[Video compression]]
*[[Dirac (video compression format)|VC-2 (Dirac)]]

==References==
{{Reflist}}

==External links==
*{{cite web | title=VC-1 Profiles and Levels | work=VC-1 | url=http://www.microsoft.com/windows/windowsmedia/forpros/events/NAB2005/VC-1.aspx#VC1_Profiles_and_Levels | access-date=December 12, 2005 }}
*{{cite web | title=Microsoft WMV Codec Implementations | work=VC-1 | url=http://www.microsoft.com/windows/windowsmedia/9series/codecs/video.aspx | access-date=February 28, 2006 }}
*[http://wiki.multimedia.cx/index.php?title=Understanding_VC-1 VC-1 reference software analysis] at the MultimediaWiki
*{{IETF RFC|4425|link=no}} – IETF RTP Payload Format for Video Codec 1
*{{cite web | title=VC-1 Decode License Announcement | work=VC-1 | url=http://www.raspberrypi.org/archives/1839 | access-date=August 24, 2012 | archive-date=October 4, 2013 | archive-url=https://web.archive.org/web/20131004233225/http://www.raspberrypi.org/archives/1839 | url-status=dead }} for the Raspberry Pi

{{Compression formats}}
{{High-definition}}
{{HD DVD}}
{{SMPTE standards}}

{{DEFAULTSORT:Vc-1}}
[[Category:American inventions]]
[[Category:HD DVD]]
[[Category:High-definition television]]
[[Category:Japanese inventions]]
[[Category:Microsoft initiatives]]
[[Category:Open standards covered by patents]]
[[Category:Microsoft Silverlight]]
[[Category:SMPTE standards]]
[[Category:South Korean inventions]]
[[Category:Video codecs]]
[[Category:Video compression]]