INTERNATIONAL ORGANISATION FOR STANDARDISATION
ORGANISATION INTERNATIONALE DE NORMALISATION
ISO/IEC JTC1/SC29/WG11
CODING OF MOVING PICTURES AND AUDIO
ISO/IEC JTC1/SC29/WG11 W13533
April 2012, Incheon, KR
Source: Communication Group
Title: White paper on MPEG-DASH Standard
Author: Iraj Sodagar
MPEG-DASH: The Standard for Multimedia Streaming Over Internet
1
Iraj Sodagar
Microsoft Corporation, 1 Microsoft Way, Redmond, WA, USA 98052
Watching the Olympics live over the Internet? Streaming last week’s episode of your favorite TV show to your game
console? Watching a 24-hours news TV channel on your mobile phone? These use cases might already seem possible as
parts of our daily lives. In fact, during the 2008 Olympics, NBC reported delivering of 3.4 petabytes of video content
over the Internet [1]. But multimedia streaming over the Internet is still its infancy compared to its potential market.
One reason is that today every commercial platform is a closed system: it has its own manifest and content formats and
streaming protocols. In other words, there is no interoperability between devices and servers of various vendors. A
recent study indicated that in a few years video content could make up the vast majority of Internet traffic [2]. One of
the main enablers would be an adopted standard that provides interoperability between various servers and devices.
Achieving such interoperability will be instrumental for the growth of the market, since a common ecosystem of content
and services will be able to provision a broad range of devices such as PCs, TVs, laptops, set-top boxes, game consoles,
tablets and mobiles phones. MPEG-DASH was developed to do just that.
Why HTTP Streaming?
Delivery of video content over the Internet had started in the 1990s with timely delivery and consumption of large
amounts of data being the main challenge. The IETF’s Real-time Transport Protocol (RTP) was designed to define
packet formats for audio and video content along with stream session management which allowed delivery of those
packets with very low overhead. RTP works well in managed IP networks. However, in today’s Internet, managed
networks have been replaced by Content Delivery Networks (CDN), many of which do not support RTP streaming. In
addition, RTP packets are often not allowed through firewalls. Finally, RTP streaming requires the server to manage a
separate streaming session for each client, making large scale deployments resource intensive.
With the increase of Internet bandwidth and the tremendous growth of the World Wide Web, the value of delivering
audio or video data in very small packets has diminished. Multimedia content can now be delivered very efficiently in
larger segments (in contrast to small packets) using HTTP. HTTP streaming has several benefits. First, Internet
infrastructure has evolved to efficiently support HTTP. For instance, CDNs provide localized “edge” caches which
reduce long-haul traffic. Also, HTTP is “firewall friendly” since almost all firewalls are configured to support its
outgoing connections. HTTP server technology is a commodity and therefore supporting HTTP streaming for millions
of users is very cost effective. Second, with HTTP streaming the client manages the streaming without the need of
maintaining a session state on the server. Therefore, provisioning a large number of streaming clients does not impose
any additional cost on server resources beyond standard web usage of HTTP and can be managed by a CDN using
standard HTTP optimization techniques.
Because of the above reasons, HTTP streaming has become a popular approach in commercial deployments. For
instance, streaming platforms such as Apple’s HTTP Live Streaming (HLS) [3], Microsoft’s Smooth Streaming [4], and
Adobe’s HTTP Dynamic Streaming [5] all use HTTP streaming as their underlying method of delivery. However, each
implementation uses different manifest and segment formats and therefore, to receive the content from each server, a
device must support its corresponding proprietary client protocol. A standard for HTTP streaming of multimedia
1
The original article was published in IEEE Multimedia, Oct-Nov 2011. It was updated in April 2013.
