Dynamic Adaptive Streaming over HTTP (DASH), also known as MPEG-DASH, is an adaptive bitrate streaming technique that enables high quality streaming of media content over the Internet delivered from conventional HTTP web servers. Similar to Apple's HTTP Live Streaming (HLS) solution, MPEG-DASH works by breaking the content into a sequence of small segments, which are served over HTTP. An early HTTP web server based streaming system called SProxy was developed and deployed in the Hewlett Packard Laboratories in 2006.[2][3] It showed how to use HTTP range requests to break the content into small segments. SProxy shows the effectiveness of segment based streaming, gaining best Internet penetration due to the wide deployment of firewalls, and reducing the unnecessary traffic transmission if a user chooses to terminate the streaming session earlier before reaching the end. Each segment contains a short interval of playback time of content that is potentially many hours in duration, such as a movie or the live broadcast of a sport event. The content is made available at a variety of different bit rates, i.e., alternative segments encoded at different bit rates covering aligned short intervals of playback time. While the content is being played back by an MPEG-DASH client, the client uses a bit rate adaptation (ABR) algorithm[4] to automatically select the segment with the highest bit rate possible that can be downloaded in time for playback without causing stalls or re-buffering events in the playback.[5] The current MPEG-DASH reference client dash.js[6] offers both buffer-based (BOLA[7]) and hybrid (DYNAMIC[5]) bit rate adaptation algorithms. Thus, an MPEG-DASH client can seamlessly adapt to changing network conditions and provide high quality playback with few stalls or re-buffering events.
MPEG-DASH is the first adaptive bit-rate HTTP-based streaming solution that is an international standard.[8] MPEG-DASH should not be confused with a transport protocol — the transport protocol that MPEG-DASH uses depends on which version of HTTP is used: TCP over HTTP and HTTP/2, or UDP over HTTP/3. MPEG-DASH uses existing HTTP web server infrastructure that is used for delivery of essentially all World Wide Web content. It allows devices like Internet-connected televisions, TV set-top boxes, desktop computers, smartphones, tablets, etc. to receive multimedia content (video, TV, radio, etc.) delivered via the Internet, coping with variable Internet receiving conditions. Standardizing an adaptive streaming solution is meant to provide confidence to the market that the solution can be adopted for universal deployment, compared to similar but more proprietary solutions like Smooth Streaming by Microsoft, or HDS by Adobe. Unlike HDS, or Smooth Streaming, DASH is codec-agnostic, which means it can use content encoded with any coding format, such as H.265, H.264, VP9, etc.[9]
Standardization
MPEG-DASH technology was developed under MPEG. Work on DASH started in 2010; it became a Draft International Standard in January 2011, and an International Standard in November 2011.[8][10] The MPEG-DASH standard was published in April, 2012 but has been revised in 2019 and then once more in 2022 as [1].
The DASH Industry Forum (DASH-IF)[13] further promotes and catalyzes the adoption of MPEG-DASH and helps transition it from a specification into a real business. It consists of major streaming and media companies, including Microsoft, Netflix, Google, Ericsson, Samsung, Adobe, etc. and creates guidelines on the usage of DASH for different use cases in practice.
MPEG-DASH is integrated in other standards, e.g. MPEG-DASH is supported in HbbTV (as of Version 1.5).[14]
Overview
DASH is an adaptive bitrate streaming technology where a multimedia file is partitioned into one or more segments and delivered to a client using HTTP.[15] A media presentation description (MPD) describes segment information (timing, URL, media characteristics like video resolution and bit rates), and can be organized in different ways such as SegmentList, SegmentTemplate, SegmentBase and SegmentTimeline, depending on the use case. Segments can contain any media data, however the specification provides specific guidance and formats for use with two types of containers: ISO base media file format (e.g. MP4 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[16] and QoE (Quality of Experience) fairness.[17] DASH standard does not specify the adaptive bitrate streaming (ABR) logic.[18] DASH is also agnostic to the underlying application layer protocol. Thus, DASH can be used with any protocol, e.g., DASH over CCN.[19]
On July 27, 2015, MPEG LA announced a call for MPEG-DASH-related patents in order to create a single patent pool for this technology.[20] MPEG LA announced its MPEG-DASH patent portfolio licence. MPEG-LA claims that the included patents are essential to the MPEG Dynamic Adaptive Streaming over HTTP standard.[21]
MPEG-DASH is available natively on Android through the ExoPlayer,[22] on Samsung Smart TVs 2012+, LG Smart TV 2012+, Sony TV 2012+, Philips NetTV 4.1+, Panasonic Viera 2013+ and Chromecast.[23] YouTube as well as Netflix already support MPEG-DASH, and different MPEG-DASH players are available.[24]
While MPEG-DASH isn't directly supported in HTML5, there are JavaScript implementations of MPEG-DASH which allow using MPEG-DASH in web browsers using the HTML5 Media Source Extensions (MSE).[25] There are also JavaScript implementations such as the bitdash player[26] which support DRM for MPEG-DASH using the HTML5 Encrypted Media Extensions.[27] In combination with WebGL, the HTML5-based adaptive bitrate streaming of MPEG-DASH enables also the efficient streaming of 360° video for live and on-demand use cases.[28]
Clients and libraries
Shaka Player, is the open source DASH HTML5 video player from Google for Low Bandwidth Connections.[29][30][31][32][33]
The cross-platform FOSS multimedia framework GStreamer has supported MPEG-DASH and WebM DASH since at least v1.4.[37]
The open-source library libdash[38] is platform independent and runs on mobile platforms such as Android, iOS, Windows Phone.
bitmovin provides the bitdash MPEG-DASH player for HTML5 and Flash.[39]
VideoJS is an open-source HTML5 video player, supports HLS, DASH, WebM, and progressive MP4 for Live and VOD streaming.[29][30]
Clappr is an open-source HTML5 video player, uses HTMLVideoElement, supports DASH, HLS, progressive, ad insertion, dynamic overlays, picture-in-picture[30][29]
Servers
Note that no specific support is required from the server for DASH content, with the exception of Live Streaming.
Wowza Streaming Engine has support MPEG-DASH playback with DVR and provides DASH Stream Target publishing to Akamai.[40]
Brightcove Zencoder has support for MPEG-DASH transmuxing/transcoding.[41]
ITEC offers a validation service for MPEG-DASH Media Presentation Description (MPD) files[34]
Multiple DASH datasets[56] are offered by the Institute of Information Technology (ITEC) at Alpen-Adria University Klagenfurt,[51][57] the GPAC group at Telecom ParisTech[52] and Digital TV Labs.[58]
The BBC has DASH test streams, including DASH over HTTP/2.[59]
Windows 10 used to have native support for DASH streaming in EdgeHTML, a proprietary browser engine that was used in Microsoft Edge (now referred to as Edge Legacy) before the transition to the Chromium-based Blink browser engine. Edge Legacy was included in Windows 10 up till version 2004. It was replaced by Edge Chromium in version 20H2.
DASH support on other browsers & operating systems is available via Media Source Extensions.
^Zhang, Bo; Teixeira, Thiago; Reznik, Yuriy (24 June 2021). "Performance of Low-Latency HTTP-based Streaming Players". Proceedings of the 12th ACM Multimedia Systems Conference. pp. 356–362. doi:10.1145/3458305.3478442. ISBN9781450384346. S2CID237596948.
