SMPTE 421, informally known as VC-1, is a

video coding format A video coding format (or sometimes video compression format) is a content representation format of digital video content, such as in a data file or bitstream. It typically uses a standardized video compression algorithm, most commonly based on ...

. Most of it was initially developed as

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 video format Windows Media Video 9 in 2003. With some enhancements including the development of a new Advanced Profile, it was officially approved as an

SMPTE The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded by Charles Francis Jenkins in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association of engineers, technologists, and e ...

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 A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling discl ...

s that applied to the technology, including

Panasonic is a Japanese multinational electronics manufacturer, headquartered in Kadoma, Osaka, Kadoma, Japan. It was founded in 1918 as in Fukushima-ku, Osaka, Fukushima by Kōnosuke Matsushita. The company was incorporated in 1935 and renamed and c ...

LG Electronics LG Electronics Inc. () is a South Korean Multinational corporation, multinational major appliance and consumer electronics corporation headquartered in Yeouido-dong, Seoul, South Korea. LG Electronics is a part of LG, LG Corporation, the fourth ...

and

Samsung Electronics Samsung Electronics Co., Ltd. (SEC; stylized as SΛMSUNG; ) is a South Korean multinational major appliance and consumer electronics corporation founded on 13 January 1969 and headquartered in Yeongtong District, Suwon, South Korea. It is curr ...

. VC-1 is supported in the now-deprecated Microsoft Silverlight, the briefly-offered

HD DVD HD DVD (short for High Density Digital Versatile Disc) is an obsolete high-density optical disc format for storing data and playback of high-definition video.

disc format, and the

Blu-ray Disc Blu-ray (Blu-ray Disc or BD) is a Digital media, digital optical disc data storage format designed to supersede the DVD format. It was invented and developed in 2005 and released worldwide on June 20, 2006, capable of storing several hours of ...

format.

Format

VC-1 is an evolution of the conventional block-based motion-compensated hybrid video coding design also found in H.261, MPEG-1 Part 2, H.262/MPEG-2 Part 2, H.263, and

MPEG-4 Part 2 MPEG-4 Part 2, MPEG-4 Visual (formally International Organization for Standardization, ISO/International Electrotechnical Commission, IEC 14496-2) is a video encoding specification designed by the Moving Picture Experts Group (MPEG). It belongs to ...

. It was widely characterized as an alternative to the

ITU-T The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is one of the three Sectors (branches) of the International Telecommunication Union (ITU). It is responsible for coordinating Standardization, standards fo ...

and

MPEG The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by International Organization for Standardization, ISO and International Electrotechnical Commission, IEC that sets standards for media coding, includ ...

video codec standard known as H.264/MPEG-4 AVC. The Advanced Profile of VC-1 contains tools designed for coding

interlaced Interlaced video (also known as interlaced scan) is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. Th ...

video sequences as well as

progressive scan Progressive scanning (alternatively referred to as noninterlaced scanning) is a format of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence. This is in contrast to interlaced video us ...

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 In high-definition television (HDTV) and video display technology, 1080i is a video display format with 1080 lines of vertical resolution and Interlaced video, interlaced scanning method. This format was once a standard in HDTV. It was particular ...

format. Both

HD DVD HD DVD (short for High Density Digital Versatile Disc) is an obsolete high-density optical disc format for storing data and playback of high-definition video.

and

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 Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...

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. Microsoft designated VC-1 as the

Xbox 360 The Xbox 360 is a home video game console developed by Microsoft. As the successor to the Xbox (console), original Xbox, it is the second console in the Xbox#Consoles, Xbox series. It was officially unveiled on MTV on May 12, 2005, with detail ...

video game console A video game console is an electronic device that Input/output, outputs a video signal or image to display a video game that can typically be played with a game controller. These may be home video game console, home consoles, which are generally ...

's official video format, and game developers could use VC-1 for

full motion video Full-motion video (FMV) is a video game narration technique that relies upon pre-recorded video files (rather than Sprite (computer graphics), sprites, vector graphics, vectors, or 3D models) to display action in the game. While many games featur ...

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 The PlayStation 3 (PS3) is a home video game console developed and marketed by Sony Computer Entertainment (SCE). It is the successor to the PlayStation 2, and both are part of the PlayStation brand of consoles. The PS3 was first released on ...

console and the

FFmpeg FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing vide ...

project also includes a VC-1 decoder. On August 24, 2012, the

Raspberry Pi Raspberry Pi ( ) is a series of small single-board computers (SBCs) developed in the United Kingdom by the Raspberry Pi Foundation in collaboration with Broadcom Inc., Broadcom. To commercialize the product and support its growing demand, the ...

Foundation announced hardware decoding support for VC-1.

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 four character code.

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." A number of high definition movies and videos have been released commercially in a format dubbed WMV HD. These titles are encoded with WMV3 Main Profile @ High Level (MP@HL).

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 Windows Media Player (WMP, officially referred to as Windows Media Player Legacy to retronym, distinguish it from Windows Media Player (2022), the new Windows Media Player introduced with Windows 11) is the first media player (application soft ...

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, also known as Windows Media Video 9 Advanced Profile, implements a more recent and fully compliant Advanced Profile of the VC-1 codec standard. It 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. The Windows Media Video 9 Advanced Profile codec also offers this same improvement in encoding efficiency with interlaced contents. A decoder for WVC1 is included in 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

Bit rates and resolutions

Other implementations

Due to its origins in Microsoft's WMV9 codec, the most popular implementations of VC-1 encoders have so far been done by Microsoft, though third-party implementations exist as well. Sonic Cinevision PSE, a professional VC-1 encoding tool used predominantly in

HD DVD HD DVD (short for High Density Digital Versatile Disc) is an obsolete high-density optical disc format for storing data and playback of high-definition video.

and

Blu-ray Blu-ray (Blu-ray Disc or BD) is a digital optical disc data storage format designed to supersede the DVD format. It was invented and developed in 2005 and released worldwide on June 20, 2006, capable of storing several hours of high-defin ...

encoding, is a commercial version of Microsoft's PEP (Parallel Encoder) encoding tool and VC-1 Analyzer tool. Microsoft owns the code development whereas

Sonic Solutions Sonic Solutions was an American computer software company headquartered in Novato, California. In addition to having a number of offices in the U.S., the company also maintained offices in Europe and Asia. It was acquired by Rovi Corporation in 2 ...

owns the sales and distribution. Microsoft 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. The

project includes a free VC-1 decoder.

Encoding software

Windows Media Encoder Windows Media Encoder (WME) is a discontinued, freeware Multimedia, media codec, encoder developed by Microsoft which enables content developers to convert or capture both live and prerecorded audio, video, and computer screen images to Windows Me ...

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 Expression Studio supports encoding VC-1 video to the Windows Media ( ASF) file format and the IIS Smooth Streaming format. Video encoder products made by Inlet, Digital Rapids,

Harmonic In physics, acoustics, and telecommunications, a harmonic is a sinusoidal wave with a frequency that is a positive integer multiple of the ''fundamental frequency'' of a periodic signal. The fundamental frequency is also called the ''1st har ...

, 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 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 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 GPUs. The former is typically found in consumer electronics devices such as

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.

hardware prior to Raspberry Pi 4 supports VC-1 hardware-accelerated decoding, although it requires purchasing of a license key.

Legal status

Although heavily associated with

, there are 18 member companies within the VC-1 patent pool. The majority of patents are held by four companies: Microsoft (324 patents),

(122 patents),

(96 patents), and

(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

MPEG LA MPEG LA was an American company based in Denver, Colorado that licensed patent pools covering essential patents required for use of the MPEG-2, MPEG-4, IEEE 1394, VC-1, ATSC, MVC, MPEG-2 Systems, AVC/H.264 and HEVC standards. Via Licensin ...

, the LLC licensing body or directly to its members, who claim to hold essential patents on the format (since it is a non-exclusive licensing body). Over 92.9% of the patents have expired as of November 26, 2024.

Patent holders

The following organizations hold one or more patents in the VC-1 patent pool, as listed by

References

External links

* *
VC-1 reference software analysis
at the MultimediaWiki * – IETF RTP Payload Format for Video Codec 1 * for the Raspberry Pi {{DEFAULTSORT:Vc-1 American inventions HD DVD High-definition television Japanese inventions Microsoft initiatives Open standards covered by patents Microsoft Silverlight SMPTE standards South Korean inventions Video codecs Video compression

Format

Microsoft codec implementations

WMV3

WMVA

WVC1

Profiles

Bit rates and resolutions

Other implementations

Encoding software

Hardware-based encoding and decoding

Legal status

Patent holders

See also

References

External links