Dynamic Adaptive Streaming over HTTP
Encyclopedia
Dynamic Adaptive Streaming over HTTP (DASH) is a multimedia streaming technology currently being developed under MPEG. Work on DASH started in 2010; it became a Draft International Standard in January 2011, and it is expected to become an International Standard in November 2011.
technology where a multimedia
file is partitioned into one or more segments and delivered to a client using HTTP.
A media presentation description (MPD) describes segment information (timing, URL, media characteristics such as video resolution
and bit rates
).
Segments can contain any media data, however the specification provides specific guidance and formats for use with two types of containers: MPEG-4 file format
or MPEG-2 Transport Stream.
DASH is audio/video codec
agnostic. One or more representations (i.e., versions at different resolutions or bit rates) of multimedia files are typically available, and selection can be made based on network
conditions, device capabilities and user preferences, enabling adaptive bitrate streaming.
DASH is a technology related to Adobe Systems
's HTTP Dynamic Streaming, Apple Inc.'s HTTP Live Streaming
(HLS) and Microsoft
's Smooth Streaming. DASH is based on Adaptive HTTP streaming (AHS) in 3GPP
Release 9 and on HTTP Adaptive Streaming (HAS) in Open IPTV Forum Release 2.
As part of their collaboration with MPEG, 3GPP Release 10 has adopted DASH (with specific codecs and operating modes) for use over wireless networks.
The first DASH player implementations are the DASH VLC plugin of the Institute of Information Technology (ITEC) at Alpen-Adria University Klagenfurt and the multimedia framework of the GPAC group at Telecom ParisTech. Content generation is possible using MP4Box from GPAC or the wrapper tool DASHEncoder (also of ITEC) .
Overview
DASH is a multimedia streamingStreaming media
Streaming media is multimedia that is constantly received by and presented to an end-user while being delivered by a streaming provider.The term "presented" is used in this article in a general sense that includes audio or video playback. The name refers to the delivery method of the medium rather...
technology where a multimedia
Multimedia
Multimedia is media and content that uses a combination of different content forms. The term can be used as a noun or as an adjective describing a medium as having multiple content forms. The term is used in contrast to media which use only rudimentary computer display such as text-only, or...
file is partitioned into one or more segments and delivered to a client using HTTP.
A media presentation description (MPD) describes segment information (timing, URL, media characteristics such as video resolution
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
and bit rates
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
).
Segments can contain any media data, however the specification provides specific guidance and formats for use with two types of containers: MPEG-4 file format
ISO base media file format
ISO base media file format defines a general structure for time-based multimedia files such as video and audio. It is used as the basis for other media file formats...
or MPEG-2 Transport Stream.
DASH is audio/video codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
agnostic. One or more representations (i.e., versions at different resolutions or bit rates) of multimedia files are typically available, and selection can be made based on network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
conditions, device capabilities and user preferences, enabling adaptive bitrate streaming.
DASH is a technology related to Adobe Systems
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
's HTTP Dynamic Streaming, Apple Inc.'s HTTP Live Streaming
HTTP Live Streaming
HTTP Live Streaming is an HTTP-based media streaming communications protocol implemented by Apple Inc. as part of their QuickTime X and iPhone software systems. It works by breaking the overall stream into a sequence of small HTTP-based file downloads, each download loading one short chunk of an...
(HLS) and Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
's Smooth Streaming. DASH is based on Adaptive HTTP streaming (AHS) in 3GPP
3GPP
The 3rd Generation Partnership Project is a collaboration between groups of telecommunications associations, known as the Organizational Partners...
Release 9 and on HTTP Adaptive Streaming (HAS) in Open IPTV Forum Release 2.
As part of their collaboration with MPEG, 3GPP Release 10 has adopted DASH (with specific codecs and operating modes) for use over wireless networks.
The first DASH player implementations are the DASH VLC plugin of the Institute of Information Technology (ITEC) at Alpen-Adria University Klagenfurt and the multimedia framework of the GPAC group at Telecom ParisTech. Content generation is possible using MP4Box from GPAC or the wrapper tool DASHEncoder (also of ITEC) .