by David Iffland on Jan 29, 2015 | Discuss ShareShare |
YouTube launched their experimental HTML5 video player in January 2010.
After five years of working with other browser vendors and the community,
they announced that HTML5 videos are now served by default for certain
browsers, casting aside the previous Adobe Flash video player.
In a blog post, YouTube Engineering Manager Richard Leider said that
Adaptive Bitrate (ABR) technology support was a key factor to their decision:
Adaptive Bitrate (ABR) streaming is critical for providing a quality video
experience for viewers - allowing us to quickly and seamlessly adjust
resolution and bitrate in the face of changing network conditions.
The ABR in question is Dynamic Adaptive Streaming over HTTP, known as MPEG-
DASH. According to Ross Gardler of Microsoft Open Technologies, MPEG-DASH
reduces the need for buffering:
With MPEG-DASH, the video stream will automatically drop to a lower
definition when the network becomes congested. This reduces the likelihood
of the viewer seeing a "paused" video while the player downloads the next
few seconds to play (aka buffering). As network congestion reduces, the
video player will in turn return to a higher quality stream.
Indeed, Leider says that "ABR has reduced buffering by more than 50 percent
globally and as much as 80 percent on heavily-congested networks." In a 2014
interview, Leider said that "YouTube playback uses DASH on TVs, game
consoles, set-top boxes, Chromecast, desktop browsers, mobile web, [and]
mobile handsets."
MPEG-DASH playback is available in browsers that support the W3C Media
Source Extensions (MSE), which is why the YouTube HTML5 player switch is
limited to Chrome, IE 11, Safari 8, and some beta versions of Firefox.
According to the specification, MSE "allows JavaScript to dynamically
construct media streams for
