YouTube

YouTube is a video-sharing website, created by three former PayPal employees in February 2005, on which users can upload, view and share videos.

The company is based in San Bruno, California, and uses Adobe Flash Video and HTML5 technology to display a wide variety of user-generated video content, including movie clips, TV clips, and music videos, as well as amateur content such as video blogging and short original videos. Most of the content on YouTube has been uploaded by individuals, although media corporations including CBS, BBC, VEVO, Hulu, and other organizations offer some of their material via the site, as part of the YouTube partnership program.

Unregistered users may watch videos, and registered users may upload an unlimited number of videos. Videos that are considered to contain potentially offensive content are available only to registered users 18 years old and older.

In November 2006, YouTube, LLC was bought by Google Inc. for US$1.65 billion, and now operates as a subsidiary of Google.

Playback
Viewing YouTube videos on a personal computer requires the Adobe Flash Player plug-in to be installed on the browser. The Adobe Flash Player plug-in is one of the most common pieces of software installed on personal computers and accounts for almost 75% of online video material.

In January 2010, YouTube launched an experimental version of the site that uses the built-in multimedia capabilities of web browsers supporting the HTML5 standard. This allows videos to be viewed without requiring Adobe Flash Player or any other plug-in to be installed. The YouTube site has a page that allows supported browsers to opt in to the HTML5 trial. Only browsers that support HTML5 Video using the H.264 or WebM formats can play the videos, and not all videos on the site are available.

Uploading
All YouTube users can upload videos up to 15 minutes in duration. Users who have a good track record of complying with the site's Community Guidelines may be offered the ability to upload videos of unlimited length, which requires verifying the account, normally through a mobile phone. When YouTube was launched in 2005, it was possible to upload long videos, but a ten-minute limit was introduced in March 2006 after YouTube found that the majority of videos exceeding this length were unauthorized uploads of television shows and films. The 10-minute limit was increased to 15 minutes in July 2010. File size is limited to 2 GB for uploads from YouTube web page, and to 20 GB if Java-based Advanced Uploader is used.

YouTube accepts videos uploaded in most container formats, including .AVI, .MKV, .MOV, .MP4, DivX, .FLV, and .ogg and .ogv. These include video formats such as MPEG-4, MPEG, VOB, and .WMV. It also supports 3GP, allowing videos to be uploaded from mobile phones. Videos with progressive scanning or interlaced scanning can be uploaded, but for the best video quality, YouTube prefers interlaced videos to be deinterlaced prior to uploading. All the video formats on YouTube use progressive scanning.

Quality and codecs
YouTube originally offered videos at only one quality level, displayed at a resolution of 320x240 pixels using the Sorenson Spark codec (a variant of H.263), with mono MP3 audio. In June 2007, YouTube added an option to watch videos in 3GP format on mobile phones. In March 2008, a high quality mode was added, which increased the resolution to 480x360 pixels. In November 2008, 720p HD support was added. At the time of the 720p launch, the YouTube player was changed from a 4:3 aspect ratio to a widescreen 16:9. With this new feature, YouTube began a switchover to H.264/MPEG-4 AVC as its default video compression format. In November 2009, 1080p HD support was added. In July 2010, YouTube announced that it had launched a range of videos in 4K format, which allows a resolution of up to 4096x3072 pixels.

YouTube videos are available in a range of quality levels. The former names of standard quality (SQ), high quality (HQ) and high definition (HD) have been replaced by numerical values representing the vertical resolution of the video. The default video stream is encoded in H.264/MPEG-4 AVC format, with stereo AAC audio.

1 fmt was an undocumented URL parameter that allowed selecting YouTube quality mode without using player user interface. Since December 2010, this parameter is no longer supported. 2 Approximate values based on statistical data; actual bitrate can be higher or lower due to variable encoding rate.

3D videos
In a video posted on July 21, 2009, YouTube software engineer Peter Bradshaw announced that YouTube users can now upload 3D videos. The videos can be viewed in several different ways, including the common anaglyph (cyan/red lens) method which utilizes glasses worn by the viewer to achieve the 3D effect. The YouTube Flash player can display stereoscopic content interleaved in rows, columns or a checkerboard pattern, side-by-side or anaglyph using a red/cyan, green/magenta or blue/yellow combination. In May 2011, an HTML5 version of the YouTube player began supporting side-by-side 3D footage that is compatible with Nvidia 3D Vision.

Content accessibility
One of the key features of YouTube is the ability of users to view its videos on web pages outside the site. Each YouTube video is accompanied by a piece of HTML, which can be used to embed it on a page outside the YouTube website. This functionality is often used to embed YouTube videos in social networking pages and blogs. Embedding, as well as ranking and commenting, can be disabled by the video owner.

YouTube does not usually offer a download link for its videos, and intends for them to be viewed through its website interface. A small number of videos, such as the weekly addresses by President Barack Obama, can be downloaded as MP4 files. Numerous third-party web sites, applications and browser plug-ins allow users to download YouTube videos. In February 2009, YouTube announced a test service, allowing some partners to offer video downloads for free or for a fee paid through Google Checkout.

Community policy
YouTube has a set of community guidelines aimed to reduce abuse of the site's features. Generally prohibited material includes sexually explicit content, videos of animal abuse, shock videos, content uploaded without the copyright holder's consent, hate speech, spam, and predatory behaviour. Despite the guidelines, YouTube has faced criticism from news sources for content in violation of these guidelines.

Copyrighted material
At the time of uploading a video, YouTube users are shown a screen with the message "Do not upload any TV shows, music videos, music concerts or advertisements without permission, unless they consist entirely of content that you created yourself". Despite this advice, there are still many unauthorized clips of copyrighted material on YouTube. YouTube does not view videos before they are posted online, and it is left to copyright holders to issue a takedown notice pursuant to the terms of the Digital Millennium Copyright Act.

Organizations including Viacom, Mediaset, and the English Premier League have filed lawsuits against YouTube, claiming that it has done too little to prevent the uploading of copyrighted material. Viacom, demanding $1 billion in damages, said that it had found more than 150,000 unauthorized clips of its material on YouTube that had been viewed "an astounding 1.5 billion times". YouTube responded by stating that it "goes far beyond its legal obligations in assisting content owners to protect their works". During the same court battle, Viacom won a court ruling requiring YouTube to hand over 12 terabytes of data detailing the viewing habits of every user who has watched videos on the site. The decision was criticized by the Electronic Frontier Foundation, which called the court ruling "a setback to privacy rights". In June 2010, Viacom's lawsuit against Google was rejected in a summary judgment, with U.S. federal Judge Louis L. Stanton stating that Google was protected by provisions of the Digital Millennium Copyright Act. Viacom announced its intention to appeal the ruling. Since Viacom filed its lawsuit in 2008, YouTube has introduced the "Video ID" system, which checks uploaded videos against a database of copyrighted content with the aim of reducing violations.

In August 2008, a US court ruled in Lenz v. Universal Music Corp. that copyright holders cannot order the removal of an online file without first determining whether the posting reflected fair use of the material. The case involved Stephanie Lenz from Gallitzin, Pennsylvania, who had made a home video of her 13-month-old son dancing to Prince's song "Let's Go Crazy", and posted the 29-second video on YouTube.

In the case of Smith v. Summit Entertainment LLC, Matt Smith sued Summit Entertainment for the wrongful use of copyright takedown notice on YouTube. He asserted seven courses of action and four were ruled in Smith's favor.

Controversial content
YouTube has also faced criticism over the offensive content in some of its videos. The uploading of videos containing defamation, pornography, and material encouraging criminal conduct is prohibited by YouTube's terms of service. Controversial areas have included Holocaust denial and the Hillsborough disaster, in which 96 football fans from Liverpool were crushed to death in 1989.

YouTube relies on its users to flag the content of videos as inappropriate, and a YouTube employee will view a flagged video to determine whether it violates the site's terms of service. In July 2008, the Culture and Media Committee of the House of Commons of the United Kingdom stated that it was "unimpressed" with YouTube's system for policing its videos, and argued that "proactive review of content should be standard practice for sites hosting user-generated content". YouTube responded by stating:

"We have strict rules on what's allowed, and a system that enables anyone who sees inappropriate content to report it to our 24/7 review team and have it dealt with promptly. We educate our community on the rules and include a direct link from every YouTube page to make this process as easy as possible for our users. Given the volume of content uploaded on our site, we think this is by far the most effective way to make sure that the tiny minority of videos that break the rules come down quickly." In October 2010, U.S. Congressman Anthony Weiner urged YouTube to take down from its website videos of imam Anwar al-Awlaki, saying that by hosting al-Awlaki's messages, "We are facilitating the recruitment of homegrown terror". British security minister Pauline Neville-Jones commented: "These Web sites would categorically not be allowed in the U.K. They incite cold-blooded murder, and as such are surely contrary to the public good." In November 2010, YouTube removed from its site some of the hundreds of videos featuring al-Awlaki's calls to jihad. It stated that it had removed videos that violated the site’s guidelines prohibiting "dangerous or illegal activities such as bomb-making, hate speech and incitement to commit violent acts", or came from accounts "registered by a member of a designated foreign terrorist organization". In December 2010, YouTube added "promotes terrorism" to the list of reasons that users can give when flagging a video as inappropriate.

User comments
Most videos enable users to leave comments, and these have attracted attention for the negative aspects of both their form and content. When Time in 2006 praised Web 2.0 for enabling "community and collaboration on a scale never seen before", it added that YouTube "harnesses the stupidity of crowds as well as its wisdom. Some of the comments on YouTube make you weep for the future of humanity just for the spelling alone, never mind the obscenity and the naked hatred". The Guardian in 2009 described users' comments on YouTube as follows: "Juvenile, aggressive, misspelled, sexist, homophobic, swinging from raging at the contents of a video to providing a pointlessly detailed description followed by a LOL, YouTube comments are a hotbed of infantile debate and unashamed ignorance – with the occasional burst of wit shining through."In September 2008, The Daily Telegraph commented that YouTube was "notorious" for "some of the most confrontational and ill-formed comment exchanges on the internet", and reported on YouTube Comment Snob, "a new piece of software that blocks rude and illiterate posts".