Microsoft Announces Support for MPEG-DASH in Microsoft Media Platform
Microsoft Media Platform will support MPEG-DASH, a recently ratified ISO/IEC standard for dynamic adaptive streaming over HTTP. Microsoft plans to support DASH and other open standards as part of an industry-wide initiative to establish reliable video delivery to Internet connected devices and enable true interoperability between adaptive streaming technologies from different vendors.
Microsoft was a key contributor in the development of MPEG-DASH. Microsoft chaired the MPEG working group that developed the DASH specification, and made significant technical contributions based on extensive experience with Microsoft Smooth Streaming. Much like Smooth Streaming, DASH uses Extensible Markup Language (XML) to describe media presentations in a manifest file which references media streams stored in ISO Base Media File Format. Combined with the standard HTTP protocol and existing Web content delivery networks, the DASH standard enables a better video experience for end users by automatically adapting to varying client and network conditions during playback.
Taking advantage of similarities between Smooth Streaming and DASH, Windows Azure Media Services will add support for DASH Live Profile later this year so that both Smooth Streaming and DASH devices can access the same live and on-demand video presentations using either manifest format. This will enable a smooth (pun intended) transition to DASH for millions of devices and services currently using Smooth Streaming.
In addition to server-side support, Microsoft will also add support for DASH to all its Smooth Streaming client development kits. The first step will be to enable DASH support in the Smooth Streaming Client for Silverlight, followed by support in Smooth Streaming Client SDKs for Windows 8, iOS, Xbox, Windows Phone and Smooth Streaming Client Porting Kit for embedded devices.
Microsoft has contributed to the development of the DECE UltraViolet® video format which enables download and adaptive streaming of premium movie and TV content; and to various international broadcast standards and consortia so that a common protected video format based on DECE Common File Format, MPEG Common Encryption, and MPEG-DASH specifications will be supported by all adaptive streaming services and devices to enable reliable interoperability for consumers, just like broadcast TV and DVD.
Finally, Microsoft along with a few other key companies founded the DASH Promoters Group, whose 50 members work to catalyze DASH adoption by providing implementation guidelines, performing interoperability tests, and harmonizing various consortia activates around DASH.
Frequently Asked Questions:
Q: What is MPEG?
A: MPEG stands for “Motion Picture Experts Group”, officially designated ISO/IEC JTC 1/SC 29/WG 11. MPEG is a working group of experts formed by ISO and IEC to set digital video and audio standards. It has been responsible for the creation of many digital media standards commonly in use today, such as MP3, AAC, MPEG-2 and MPEG-4 AVC (aka H.264).
Q: What is DASH?
A: DASH stands for “Dynamic Adaptive Streaming over HTTP”, and is the name of the MPEG created standard officially designated ISO/IEC 23009-1 “Information technology — Dynamic adaptive streaming over HTTP (DASH) — Part 1: Media presentation description and segment formats.”
Q: What is Dynamic Adaptive Streaming?
A: Adaptive streaming defines media “Segments” that are a few seconds long and a manifest or playlist format that describes alternative encodings of each Segment (different bitrates, resolutions, codecs, etc.). Devices can download a sequence of Segments of compatible types (e.g. a particular video bitrate and resolution, and audio language) from a set of alternatives typically stored on Web servers.
“Dynamic” adaptation is the ability of each device to automatically switch the next Segment selection to an alternative bitrate and resolution in order to adapt to changes in network bandwidth and client conditions without interrupting the video presentation. The video quality will only be as good as the effective network bandwidth allows, but will be the best possible quality rather than some “lowest common denominator” fixed bitrate that still causes “paused for rebuffering” errors when bandwidth temporarily reduces.
Since the adaptive intelligence is inside each device and Web servers and Content Delivery Networks (CDNs) are stateless HTTP servers, DASH allows the number of clients for a particular presentation to scale to large numbers with only a small increase in server load. With the explosion of video on the Internet (projected to be 90+% of all traffic in two years), it is critical to adopt a network efficient streaming method that can cope with congestion to prevent grid lock.
Q: Why was DASH developed?
A: With the emergence of various competing HTTP-based adaptive streaming solutions over the past several years – Microsoft Smooth Streaming, Apple HTTP Live Streaming, Adobe HTTP Dynamic Streaming, to name a few – it quickly became obvious that multiple competing adaptive streaming technologies were contributing to the fragmentation of the streaming media market, increasing storage and bandwidth costs, and impairing customer reach. Efforts to standardize HTTP-based adaptive streaming began in 3GPP in 2009 and continued in MPEG shortly thereafter, successfully assembling key industry experts to collaborate on a common specification that would ultimately simplify workflows, reduce cost and increase content reach and device interoperability. DASH was ratified by ISO/IEC as a standard in November 2011.
Q: What are the benefits of DASH for consumers?
A: DASH has the potential to give consumers access to any video on any device capable of Internet access. DASH provides a framework to enable adaptive streaming appropriate for all types of devices, and further standardization of media formats and content protection can enable playback compatibility to provide universal access to Internet TV, movies, user generated video, education, communication, etc.
Q: What are the benefits of DASH for publishers?
A: DASH has the potential to give publishers access to any consumer on any video device capable of Internet access. Rather than preparing several servers and sets of content to reach different types of devices, a publisher should eventually be able to publish in a single DASH Application Profile that can be played by all devices.
Q: What Microsoft services will have DASH support?
A: Windows Azure Media Services will provide encoding, encryption, and streaming support for Application Profiles based on DASH “ISO Base Media Live Profile” this year. Both DASH manifests and Smooth Streaming manifests will be generated to allow the same media to be streamed by DASH clients and Smooth Streaming clients. The primary media format will conform to the PIFF 1.3 specification in addition to Live Profile, will include several features and constraints compatible with the DECE Common File Format, and may optionally include MPEG Common Encryption with PlayReady DRM support. Windows Azure Media Services will also be capable of live transformation to multiple streaming formats, including MPEG-2 Transport Streams for use with DASH M2TS Simple Profile manifests or M3U8 playlists.
Q: What Microsoft client technologies will have DASH support?
A: Microsoft plans to add MPEG-DASH support to all client development kits that currently support Smooth Streaming. These are: Smooth Streaming Client for Silverlight; Smooth Streaming Client for Windows Phone; Smooth Streaming Client SDK for Windows 8 Metro-style applications; Xbox LIVE Application Development Kit; Smooth Streaming SDK for iOS Devices with PlayReady; and Smooth Streaming Client Porting Kit.
Q: Is Microsoft discontinuing Smooth Streaming?
A: No. Microsoft will continue to invest in Smooth Streaming as an established technology and brand while ensuring its Smooth Streaming services, clients, tools and workflows are DASH compatible. The Smooth Streaming file format (PIFF 1.3) is already compatible with the DASH specification (ISO Base Media Live Profile) so customers and partners who are investing into creation of Smooth Streaming content today will have a clear path to making that content deliverable to DASH clients in the future.
Q: What is Common Encryption?
A: Common Encryption is an MPEG standard using AES-128 media encryption that enables a single protected ISO Base Media file or adaptive streaming presentation to be used with any DRM system supported by a device and the publisher. The standard is designated ISO/IEC 23001-7 “Information technology – MPEG systems technologies – Part 7: Common encryption in ISO base media file format files” . Prior to this standard, a different set of files was required for each different DRM type, and interchange of files between authorized devices was generally not possible because of different DRMs.
Microsoft uses this technology in Smooth Streaming, contributed it to the MPEG standard and DECE UltraViolet® Common File Format, and was the editor the MPEG standard.
Q: What is Common File Format?
A: Common File Format (CFF) is a DECE video specification titled “Common File Format & Media Formats Specification” used for content download. It specifies video files based on fragmented ISO Base Media files (MPEG-4 Part 12), optionally using Common Encryption, containing AVC video, AAC audio, SMPTE Timed Text and Graphics subtitles, metadata, and several optional audio formats. All parameters required for interoperability are sufficiently specified to allow independently implemented encoders, publishers, delivery services, and devices to reliably interchange and play the same files. Different “media profiles” are specified for high definition, standard definition, and “portable” definition devices.
The CFF requirement to use short movie fragments makes these files and compatible decoders forward compatible with DASH adaptive streaming using movie fragments as DASH Media Segments. DECE is currently in the process of specifying “Common Streaming Format” and considering DASH Application Profiles.
Q: What about HTML5 playback?
A: The current working draft of HTML5 does not include specific support for either adaptive streaming or DRM protection. It is possible to indicate a playlist or manifest file as the source of the <video> tag, but a publisher would have no control over the behavior and presentation that each device or browser would execute in response to that manifest. There are no standard APIs to integrate the presentation decisions made by the platform with a presentation application running in the browser.
Q: Where can I learn more about DASH?
A: We recommend visiting the MPEG-DASH Promoters Group website, as well as reading the following technical white papers: