company name	YouTube, LLC
company slogan	Broadcast Yourself
owner	Independent (2005–2006)Google Inc. (2006–present)
company logo
company type	Subsidiary,limited liability company
foundation	February 14, 2005
founder	Steve Chen Chad HurleyJawed Karim
area served	Worldwide
location city	901 Cherry Ave,San Bruno, California
location country
key people	Salar Kamangar, CEOChad Hurley, Advisor
screenshot
url	(see list of localized domain names)
registration	Optional (Only required for certaintasks such as viewing flagged videos,viewing flagged comments anduploading videos)
launch date
current status	Active
language	34 languages available through user interface
advertising	Google AdSense
alexa	3 ()
website type	video hosting service }}

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

Company history

YouTube was founded by Chad Hurley, Steve Chen, and Jawed Karim, who were all early employees of PayPal. Hurley had studied design at Indiana University of Pennsylvania, while Chen and Karim studied computer science together at the University of Illinois at Urbana-Champaign.

According to a story that has often been repeated in the media, Hurley and Chen developed the idea for YouTube during the early months of 2005, after they had experienced difficulty sharing videos that had been shot at a dinner party at Chen's apartment in San Francisco. Karim did not attend the party and denied that it had occurred, while Hurley commented that the idea that YouTube was founded after a dinner party "was probably very strengthened by marketing ideas around creating a story that was very digestible".

YouTube began as a venture-funded technology startup, primarily from a $11.5 million investment by Sequoia Capital between November 2005 and April 2006. YouTube's early headquarters were situated above a pizzeria and Japanese restaurant in San Mateo, California. The domain name www.youtube.com was activated on February 14, 2005, and the website was developed over the subsequent months.

The first YouTube video was entitled ''Me at the zoo'', and shows founder Karim at the San Diego Zoo. The video was uploaded on April 23, 2005, and can still be viewed on the site.

YouTube offered the public a beta test of the site in May 2005, six months before the official launch in November 2005. The site grew rapidly, and in July 2006 the company announced that more than 65,000 new videos were being uploaded every day, and that the site was receiving 100 million video views per day. According to data published by market research company comScore, YouTube is the dominant provider of online video in the United States, with a market share of around 43 percent and more than 14 billion videos viewed in May 2010. YouTube says that over 48 hours of new videos are uploaded to the site every minute, and that around three quarters of the material comes from outside the US. It is estimated that in 2007 YouTube consumed as much bandwidth as the entire Internet in 2000. Alexa ranks YouTube as the third most visited website on the Internet, behind Google and Facebook.

The choice of the name www.youtube.com led to problems for a similarly named website, www.utube.com. The owner of the site, Universal Tube & Rollform Equipment, filed a lawsuit against YouTube in November 2006 after being overloaded on a regular basis by people looking for YouTube. Universal Tube has since changed the name of its website to www.utubeonline.com. In October 2006, Google Inc. announced that it had acquired YouTube for $1.65 billion in Google stock, and the deal was finalized on November 13, 2006. Google does not provide detailed figures for YouTube's running costs, and YouTube's revenues in 2007 were noted as "not material" in a regulatory filing. In June 2008, a ''Forbes'' magazine article projected the 2008 revenue at $200 million, noting progress in advertising sales.

In November 2008, YouTube reached an agreement with MGM, Lions Gate Entertainment, and CBS, allowing the companies to post full-length films and television episodes on the site, accompanied by advertisements in a section for US viewers called "Shows". The move was intended to create competition with websites such as Hulu, which features material from NBC, Fox, and Disney. In November 2009, YouTube launched a version of "Shows" available to UK viewers, offering around 4,000 full-length shows from more than 60 partners. In January 2010, YouTube introduced an online film rentals service, which is currently available only to users in the US. The service offers over 6,000 films.

In March 2010, YouTube began free streaming of certain content, including 60 cricket matches of the Indian Premier League. According to YouTube, this was the first worldwide free online broadcast of a major sporting event.

On March 31, 2010, the YouTube website launched a new design, with the aim of simplifying the interface and increasing the time users spend on the site. Google product manager Shiva Rajaraman commented: "We really felt like we needed to step back and remove the clutter." In May 2010, it was reported that YouTube was serving more than two billion videos a day, which it described as "nearly double the prime-time audience of all three major US television networks combined". In May 2011, YouTube reported in its company blog that the site was receiving more than three billion views per day.

In October 2010, Hurley announced that he would be stepping down as chief executive officer of YouTube to take an advisory role, and that Salar Kamangar would take over as head of the company.

In April 2011, James Zern, a YouTube software engineer, revealed that 30 percent of videos accounted for 99 percent of views on the site.

Features

Video technology

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

Videos uploaded to YouTube by standard account holders are limited to 15 minutes in duration. When YouTube was launched in 2005, it was possible to upload longer 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. Partner accounts are permitted to upload longer videos, subject to acceptance by YouTube. File size is limited to 2 GB for uploads from YouTube web page, and to 20 GB if Java-based Advanced Uploader is used. In December 2010, YouTube announced that holders of standard accounts would be allowed to upload videos of unlimited length, provided that they have a good history of following the site's Community Guidelines and policy on copyright. 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.

45 ! colspan="4">MP4 style="background:#f2f2f2; text-align:left;" – 400 240 0.25 style="background:#f2f2f2; text-align:left;" 64

+Comparison of YouTube media encoding options

colspan="2" style="text-align:left;"

fmt value<

!! 5 !! 34 !! 35 !! 18 !! 22 !! 37 !! 38 !! 43 !! 44

17

FLV

|

WebM

3GP

rowspan="5" style="background:#f2f2f2; text-align:left;"

Video

Encoding ||

Sorenson H.263

MPEG-4 AVC (H.264)

VP8

MPEG-4 Visual

style="background:#f2f2f2; text-align:left;"

Profile

|

Main

Baseline

High

–

–

style="background:#f2f2f2; text-align:left;"

Max width (pixels)

|

640

854

640

1280

1920

4096

640

854

1280

176

style="background:#f2f2f2; text-align:left;"

Max height (pixels)

|

360

480

360

720

1080

3072

360

480

720

144

style="background:#f2f2f2; text-align:left;"

Bitrate (Mbit/s)

|

0.5

0.8–1.0

0.5

2.0–2.9

3.5–5.0

–

0.5

1

2

–

rowspan="4" style="background:#f2f2f2; text-align:left;"

Audio

Encoding ||

MP3

AAC

Vorbis

AAC

style="background:#f2f2f2; text-align:left;"

Channels

style="background:#f2f2f2; text-align:left;"

Sampling rate (Hz)

style="background:#f2f2f2; text-align:left;"

Bitrate (kbit/s)

|

128

96

152

128

192

–

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.

Platforms

Some smartphones are capable of accessing YouTube videos, dependent on the provider and the data plan. YouTube Mobile was launched in June 2007, and uses RTSP streaming for the video. Not all of YouTube's videos are available on the mobile version of the site.

Since June 2007, YouTube's videos have been available for viewing on a range of Apple products. This required YouTube's content to be transcoded into Apple's preferred video standard, H.264, a process that took several months. YouTube videos can be viewed on devices including Apple TV, iPod Touch and the iPhone. A TiVo service update in July 2008 allowed the system to search and play YouTube videos. In January 2009, YouTube launched "YouTube for TV", a version of the website tailored for set-top boxes and other TV-based media devices with web browsers, initially allowing its videos to be viewed on the PlayStation 3 and Wii video game consoles. In June 2009, YouTube XL was introduced, which has a simplified interface designed for viewing on a standard television screen.

Localization

On June 19, 2007, Google CEO Eric Schmidt was in Paris to launch the new localization system. The interface of the website is available with localized versions in 31 countries and a worldwide version.

! Country	! Language	! Launch date
	Spanish language
(Taiwan)
	[[Canadian English
[[South Korea
	Indian English
	Spanish
	Arabic
	Arabic
	Arabic
	Arabic
	Arabic
	Arabic

The YouTube interface suggests which local version should be chosen on the basis of the [[IP address of the user. In some cases, the message "This video is not available in your country" may appear because of copyright restrictions or inappropriate content.

The interface of the YouTube website is available in 30 different languages, including Catalan, Danish, Finnish, Greek, Hungarian, Norwegian and Slovene, which do not have local channel versions.

Plans for YouTube to create a local version in Turkey have run into problems, since the Turkish authorities asked YouTube to set up an office in Turkey, which would be subject to Turkish law. YouTube says that it has no intention of doing this, and that its videos are not subject to Turkish law. Turkish authorities have expressed concerns that YouTube has been used to post videos insulting to Mustafa Kemal Atatürk and some material offensive to Muslims.

In March 2009, a dispute between YouTube and the British royalty collection agency PRS for Music led to premium music videos being blocked for YouTube users in the United Kingdom. The removal of videos posted by the major record companies occurred after failure to reach agreement on a licensing deal. The dispute was resolved in September 2009. In April 2009, a similar dispute led to the removal of premium music videos for users in Germany.

April Fools

YouTube has featured an April Fools prank on the site on April 1 of every year since 2008: 2008: All the links to the videos on the main page were redirected to Rick Astley's music video "Never Gonna Give You Up", a prank known as "Rickrolling". 2009: When clicking on a video on the main page, the whole page turned upside down. YouTube claimed that this was a new layout. 2010: YouTube temporarily released a "TEXTp" mode, which translated the colors in the videos to random upper case letters. YouTube claimed in a message that this was done in order to reduce bandwidth costs by $1 per second. 2011: The site celebrated its "100th anniversary" with a "1911 button" and a range of sepia-toned silent, early 1900s-style films, including "Flugelhorn Feline", a parody of Keyboard Cat.

Censorship and filtering

Several countries have blocked access to YouTube, including: , YouTube is blocked in the People's Republic of China. Morocco shut down access to YouTube in 2008. Thailand blocked YouTube between 2006 and 2007 due to offensive videos relating to King Bhumibol Adulyadej. Turkey blocked access to YouTube between 2008 and 2010 after controversy over videos deemed insulting to Mustafa Kemal Atatürk. The block was lifted briefly but reimposed in November 2010. On December 3, 2006, Iran temporarily blocked access to YouTube, along with several other sites, after declaring them as violating social and moral codes of conduct. The YouTube block came after a video was posted online that appeared to show an Iranian soap opera star having sex. The block was later lifted and then reinstated after Iran's 2009 presidential election. On February 23, 2008, Pakistan blocked YouTube because of "offensive material" towards the Islamic faith, including display of the Danish cartoons of the prophet Muhammad. This led to a near global blackout of the YouTube site for around two hours, as the Pakistani block was inadvertently transferred to other countries. Pakistan lifted its block on February 26, 2008. Many Pakistanis circumvented the three-day block by using virtual private network software. In May 2010, following the Everybody Draw Mohammed Day, Pakistan again blocked access to YouTube, citing "growing sacrilegious content". On January 24, 2010, Libya blocked access to YouTube after it featured videos of demonstrations in the Libyan city of Benghazi by families of detainees who were killed in Abu Salim prison in 1996, and videos of family members of Libyan leader Muammar Gaddafi at parties. The blocking was criticized by Human Rights Watch.

Some schools have blocked access to YouTube, citing the inability to determine what sort of video material might be accessed by students.

YouTube was awarded a 2008 Peabody Award and cited for being "a 'Speakers' Corner' that both embodies and promotes democracy".

''Entertainment Weekly'' put it on its end-of-the-decade "best-of" list. It said: "Providing a safe home for piano-playing cats, celeb goof-ups, and overzealous lip-synchers since 2005."

Social impact

Before the launch of YouTube in 2005, there were few easy methods available for ordinary computer users who wanted to post videos online. With its simple interface, YouTube made it possible for anyone with an Internet connection to post a video that a worldwide audience could watch within a few minutes. The wide range of topics covered by YouTube has turned video sharing into one of the most important parts of Internet culture.

An early example of the social impact of YouTube was the success of The Bus Uncle video in 2006. It shows a heated conversation between a youth and an older man on a bus in Hong Kong, and was discussed widely in the mainstream media. Another YouTube video to receive extensive coverage is ''guitar'', which features a performance of Pachelbel's Canon on an electric guitar. The name of the performer is not given in the video. After it received millions of views ''The New York Times'' revealed the identity of the guitarist as Lim Jeong-hyun, a 23-year-old from South Korea who had recorded the track in his bedroom.

''Charlie Bit My Finger'', which was uploaded on May 22, 2007, is a viral video that has received the most views of any user generated YouTube video, with over 300 million views. The clip features two English brothers, with one-year-old Charlie biting the finger of his brother Harry, aged three. In ''Time'''s list of YouTube's 50 greatest viral videos of all time, "Charlie Bit My Finger" was ranked at number one.

Criticism

Copyrighted material

YouTube has been criticized for failing to ensure that uploaded videos comply with copyright law. 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". Since Viacom filed its lawsuit, YouTube has introduced a system called Video ID, which checks uploaded videos against a database of copyrighted content with the aim of reducing violations. 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.

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.

Privacy

In July 2008, Viacom won a court ruling requiring YouTube to hand over data detailing the viewing habits of every user who has watched videos on the site. The move led to concerns that the viewing habits of individual users could be identified through a combination of their IP addresses and log in names. The decision was criticized by the Electronic Frontier Foundation, which called the court ruling "a setback to privacy rights". U.S. District Court Judge Louis L. Stanton dismissed the privacy concerns as "speculative", and ordered YouTube to hand over documents totaling around 12 terabytes of data. Judge Stanton rejected Viacom's request that YouTube hand over the source code of its search engine, saying that it was a trade secret.

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. However, this procedure has been criticized by the United Kingdom government. 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, tied to the accused Fort Hood shooter, Christmas Day bomber, and attempted Times Square bomber, and on the U.S. targeted killing list, 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".

See also

Alternative media

CNN-YouTube presidential debates

Comparison of video hosting services

List of Internet phenomena

List of video hosting services

List of YouTube personalities

Viacom International Inc. v. YouTube, Inc.

YouTube Awards

YouTube Instant

YouTube Live

YouTube Symphony Orchestra

References

Bibliography

External links

YouTube mobile website

Category:BigTable implementations Category:Companies based in San Mateo County, California Category:Entertainment websites Category:Free music Category:Google acquisitions Category:Google services Category:Internet advertising and promotion Category:Internet companies of the United States Category:Internet properties established in 2005 Category:Multilingual websites Category:Subtitling Category:Video hosting Category:Video on demand services Category:Web 2.0

af:YouTube am:ዩ ቱብ ar:يوتيوب ast:YouTube az:Youtube bn:ইউটিউব zh-min-nan:YouTube be:YouTube be-x-old:YouTube bcl:YouTube bar:YouTube bs:YouTube bg:YouTube ca:YouTube cs:YouTube cy:YouTube da:YouTube de:YouTube et:YouTube el:YouTube es:YouTube eo:YouTube eu:YouTube fa:یوتیوب fo:Youtube fr:YouTube ga:YouTube gl:YouTube gu:યુ ટ્યુબ ko:유튜브 hy:ՅուԹյուբ hi:यू ट्यूब hsb:YouTube hr:YouTube ilo:Youtube id:YouTube ia:YouTube is:YouTube it:YouTube he:YouTube jv:YouTube kn:ಯೂಟ್ಯೂಬ್‌ pam:YouTube ka:YouTube kk:YouTube sw:YouTube ku:YouTube la:YouTube lv:YouTube lb:YouTube lt:YouTube hu:YouTube mk:YouTube ml:യൂട്യൂബ് mt:YouTube mr:यूट्यूब ms:YouTube my:ယူကျု(ဘ်) nah:YouTube nl:YouTube nds-nl:YouTube ja:YouTube no:YouTube nn:YouTube uz:YouTube pfl:YouTube pnb:یو ٹیوب pap:Youtube ps:يوټيوب km:YouTube nds:YouTube pl:YouTube pt:YouTube ro:YouTube ru:YouTube sah:YouTube stq:YouTube sq:YouTube simple:YouTube sk:YouTube sl:YouTube so:YouTube sr:Јутуб sh:YouTube fi:YouTube sv:Youtube tl:YouTube ta:யூடியூப் tt:YouTube te:యూ ట్యూబ్ th:ยูทูบ tg:YouTube tr:YouTube uk:YouTube ur:یوٹیوب vec:YouTube vi:YouTube wa:YouTube (waibe) yi:יוטוב zh-yue:YouTube diq:Youtube zh:YouTube