MPEG DASH: A Technical Deep Dive and Look at What’s Next
`Andy Salo
`RGB Networks
`
`Abstract
`
` The MPEG DASH standard was ratified in
`December 2011 and published by
`the
`International Organization
`for Standards
`(ISO) in April 2012. This paper will review
`the technical aspects of the new MPEG DASH
`standard in detail, including: how DASH
`supports live, on-demand and time-shifted
`(NDVR) services; how the two primary video
`formats –
`ISO-base media
`file
`format
`(IBMFF) and MPEG-2 TS – compare and
`contrast; how the new standard supports
`digital rights management (DRM) methods;
`and how Media Presentation Description
`(MPD) XML files differ from current adaptive
`streaming manifests. In addition, the paper
`will discuss how MPEG DASH is likely to be
`adopted by the industry, what challenges must
`still be overcome, and what the implications
`could be for cable operators and other video
`service providers (VSPs).
`
`INTRODUCTION
`
` For much of the past decade, it was quite
`difficult to stream live video to a mobile
`device. Wide
`bandwidth
`variability,
`unfavorable firewall configurations and lack
`of network infrastructure support all created
`major roadblocks to live streaming. Early,
`more traditional streaming protocols, designed
`for small packet
`formats and managed
`delivery networks, were anything but firewall-
`friendly. Although HTTP
`progressive
`download was developed partially to get
`audio and video streams past firewalls, it still
`didn’t offer true streaming capabilities.
`
` Now, the advent of adaptive streaming
`over HTTP
`technology
`has
`changed
`everything, reshaping video delivery to PCs,
`laptops, game consoles, tablets, smartphones
`
`and other mobile devices, as well as such key
`home devices as Web-connected TVs and
`pure and hybrid IP set-top boxes (STBs). As a
`result, watching video online or on the go is
`no longer a great novelty, nor is streaming
`Internet-delivered content to TV screens in
`the home. Driven by the explosion in video-
`enabled devices, consumers have swiftly
`moved through the early-adopter phase of TV
`Everywhere service, reaching the point where
`a growing number expect any media to be
`available on any device over any network
`connection
`at
`any
`time.
`Increasingly,
`consumers also expect the content delivery to
`meet the same high quality levels they have
`come to know and love from traditional TV
`services.
`
` Even though the emergence of the three
`main adaptive streaming protocols
`from
`Adobe, Apple and Microsoft over the past
`three and a half years has made multiscreen
`video a reality, significant problems still
`remain. Each of
`the
`three proprietary
`platforms is a closed system, with its own
`manifest
`format,
`content
`formats
`and
`streaming protocols. So, content creators and
`equipment vendors must
`craft
`several
`different versions of their products to serve
`the entire streaming video market, greatly
`driving up costs and restricting the market’s
`overall development.
`
` In an ambitious bid to solve these nagging
`problems, MPEG has recently adopted a new
`standard for multimedia streaming over the
`Internet. Known as MPEG Dynamic Adaptive
`Streaming over HTTP, or MPEG DASH, the
`new industry standard attempts to create a
`universal delivery format for streaming media
`by incorporating the best elements of the three
`main proprietary streaming solutions. In doing
`so, MPEG DASH aims to provide the long-
`sought
`interoperability between different
`
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`

`network servers and different consumer
`electronics devices,
`thereby
`fostering a
`common ecosystem of content and services.
`
`technical
`the
` This paper will review
`aspects of the new MPEG DASH standard in
`detail, including: how DASH supports live,
`on-demand
`and
`time-shifted
`(NDVR)
`services; how the two primary video formats
`(ISO-base media file format (IBMFF) and
`MPEG-2 TS) compare and contrast; how the
`standard supports DRM methods; and how
`Media Presentation Description (MPD) XML
`files differ from current adaptive streaming
`manifests. In addition, the paper will discuss
`how MPEG DASH is likely to be adopted by
`the industry, what challenges must still be
`overcome, and what the implications could be
`for cable operators and other video service
`providers (VSPs).
`
`AN ADAPTIVE STREAMING PRIMER
`
` As indicated previously, the delivery of
`streaming video and audio content
`to
`consumer electronics devices has come a long
`way over the past few years. Thanks to the
`introduction of adaptive streaming over
`HTTP, multimedia content can now be
`delivered more easily than ever before. In
`particular, adaptive streaming offers
`two
`critical features for video content that have
`made the technology the preferred choice for
`mobile delivery.
`
` First, adaptive streaming over HTTP
`breaks down, or segments, video programs
`into small, easy-to-download chunks. For
`example, Apple’s HTTP Live Streaming
`(HLS) protocol
`typically segments video
`content
`into 10-second
`chunks, while
`Microsoft’s
`Smooth
`Streaming
`(MSS)
`
`protocol and Adobe’s HTTP Dynamic
`Streaming (HDS) usually break video content
`into even smaller chunks of five seconds or
`less.
`
` Second, adaptive streaming encodes the
`video content at multiple bitrates and
`resolutions, creating different chunks of
`different sizes. This is the truly ‘adaptive’ part
`of adaptive streaming, as the encoding enables
`the mobile client to choose between various
`bitrates and resolutions and then adapt to
`larger or smaller chunks automatically as
`network conditions keep changing.
`
` In turn, these two key features of adaptive
`streaming lead to a number of benefits:
`
`1. Video chunks can be cached by
`proxies and easily distributed to
`content delivery networks (CDNs) or
`HTTP servers, which are simpler and
`cheaper to operate than the special
`streaming servers required for ‘older’
`video streaming technologies.
`
`2. Bitrate switching allows clients to
`adapt dynamically to network
`conditions.
`
`3. Content providers no longer have to
`guess which bitrates to encode for end
`devices.
`
`4. The technology works well with
`firewalls because the streams are sent
`over HTTP.
`
`5. Live and video-on-demand (VoD)
`workflows are almost identical. When
`a service provider creates a live
`stream, the chunks can easily be stored
`for later VoD delivery.
`
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`

`
`
`Figure 1: Content Delivery Chain for Live Adaptive Streaming
`
`
`
`
` Sensing the promise of adaptive streaming
`technology, several major technology players
`have sought to carve out large shares of the
`rapidly growing market. Most notably, the list
`now includes such prominent tech companies
`as Adobe, Apple and Microsoft.
`
` While the streaming of video using HTTP-
`delivered fragments goes back many years
`(and seems lost in the mists of time), Move
`Networks caught the attention of several
`media companies with its adaptive HTTP
`streaming technology in 2007. Move was
`quickly followed by Microsoft, which entered
`the market by releasing Smooth Streaming in
`October 2008 as part of
`its Silverlight
`architecture. Earlier
`that year, Microsoft
`demonstrated a prototype version of Smooth
`Streaming by delivering live and on-demand
`streaming content from such events as the
`Summer Olympic Games in Beijing and the
`Democratic National Convention in Denver.
`
` Smooth Streaming has all of the typical
`characteristics of adaptive streaming. The
`video content is segmented into small chunks
`and then delivered over HTTP. Usually,
`
`multiple bitrates are encoded so that the client
`can choose the best video bitrate to deliver an
`optimal viewing experience based on network
`conditions.
`
` Apple came next with HLS, originally
`unveiling it with the introduction of the
`iPhone 3.0 in mid-2009. Prior to the iPhone 3,
`no
`streaming protocols were
`supported
`natively on the iPhone, leaving developers to
`wonder what Apple had in mind for native
`streaming support. In May 2009, Apple
`proposed HLS as a standard to the Internet
`Engineering Task Force (IETF), and the draft
`is now in its eighth iteration.
`
` HLS works by segmenting video streams
`into 10-second chunks; the chunks are stored
`using a standard MPEG-2 transport stream
`file format. The chunks may be created using
`several bitrates and resolutions – so-called
`profiles – allowing a client
`to switch
`dynamically between different profiles,
`depending on network conditions.
`
` Adobe, the last of the Big Three, entered
`the adaptive streaming market in late 2009
`
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`

`with the announcement of HTTP Dynamic
`Streaming
`(HDS). Originally known as
`“Project Zeri,” HDS was introduced in June
`2010. Like MSS and HLS, HDS breaks up
`video content into small chunks and delivers
`them over HTTP. Multiple bitrates are
`encoded so that the client can choose the best
`video bitrate to deliver an optimal viewing
`experience based on network conditions.
`
`
`to Microsoft Smooth
`is closer
` HDS
`Streaming than it is to Apple’s HLS protocol.
`Primarily, this is because HDS, like MSS,
`uses a single aggregate file from which
`MPEG-4 container fragments are extracted
`and delivered.
`In contrast, HLS uses
`individual media chunks rather than one large
`aggregate file.
`
`
`
`Figure 2: Feature Comparison of Three Major Adaptive Streaming Platforms
`
`
`
`
`THE DUELING STREAMING
`PLATFORM PROBLEM
`
`
`streaming
`three major adaptive
` The
`protocols – MSS, HLS and HDS – have much
`in common. Most
`importantly, all
`three
`streaming platforms use HTTP streaming for
`their underlying delivery method, relying on
`standard HTTP Web servers instead of special
`streaming servers. They all use a combination
`of encoded media files and manifest files that
`identify the main and alternative streams and
`their respective URLs for the player. And
`their respective players all monitor either
`buffer status or CPU utilization and switch
`streams as necessary, locating the alternative
`streams from the URLs specified in the
`manifest.
`
` The overriding problem with MSS, HLS
`and HDS
`is
`that
`these
`three different
`streaming protocols, while quite similar to
`each other in many ways, are different enough
`that they are not technically compatible.
`Indeed, each of
`the
`three proprietary
`commercial platforms is a closed system with
`its own type of manifest format, content
`formats, encryption methods and streaming
`protocols, making it impossible for them to
`work together.
`
`
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`

` Take Microsoft Smooth Streaming and
`Apple’s HLS. Here are three key differences
`between the two competing platforms:
`
`
`1. HLS makes use of a regularly updated
`“moving window” metadata index file
`that tells the client which chunks are
`available for download. Smooth
`Streaming uses time codes in the
`chunk requests so that the client
`doesn’t have to keep downloading an
`index file. This leads to a second
`difference:
`
`2. HLS requires a download of an index
`file every time a new chunk is
`available. That makes it desirable to
`run HLS with longer duration chunks,
`thereby minimizing the number of
`index file downloads. So, the
`recommended chunk duration with
`HLS is 10 seconds, while it is just two
`seconds with Smooth Streaming.
`
`3. The “wire format” of the chunks is
`different. Although both formats use
`H.264 video encoding and AAC audio
`encoding, HLS makes use of MPEG-2
`Transport Stream files, while Smooth
`Streaming makes use of “fragmented”
`ISO MPEG-4 files. The “fragmented”
`MP4 file is a variant in which not all
`the data in a regular MP4 file is
`included in the file. Each of these
`formats has some advantages and
`disadvantages. MPEG-2 TS files have
`a large installed analysis toolset and
`have pre-defined signaling
`mechanisms for things like data
`signals (e.g. specification of ad
`insertion points). But fragmented MP4
`files are very flexible and can easily
`accommodate all kinds of data, such as
`decryption information, that MPEG-2
`TS files don’t have defined slots to
`carry.
`
`
`
` Or take Adobe HDS and Apple’s HLS.
`These two platforms have a number of key
`differences as well:
`
`1. HLS makes use of a regularly updated
`“moving window” metadata index
`(manifest) file that tells the client
`which chunks are available for
`download. Adobe HDS uses sequence
`numbers in the chunk requests so the
`client doesn’t have to keep
`downloading a manifest file.
`
`2. In addition to the manifest, there is a
`bootstrap file, which in the live case
`gives the updated sequence numbers
`and is equivalent to the repeatedly
`downloaded HLS playlist.
`
`3. Because HLS requires a download of a
`manifest file as often as every time a
`new chunk is available, it is desirable
`to run HLS with longer duration
`chunks, thus minimizing the number
`of manifest file downloads. More
`recent Apple client versions appear to
`check how many segments are in the
`playlist and only re-fetch the manifest
`when the client runs out of segments.
`Nevertheless, the recommended chunk
`duration with HLS is still 10 seconds,
`while it is usually just two to five
`seconds with Adobe HDS.
`
`4. The “wire format” of the chunks is
`different. Both formats use H.264
`video encoding and AAC audio
`encoding. But HLS makes use of
`MPEG-2 TS files, while Adobe HDS
`(and Microsoft SS) make use of
`“fragmented” ISO MPEG-4 files.
`
`
` Due to such differences, there is no such
`thing as a universal delivery standard for
`streaming media today. Likewise, there is no
`universal encryption standard or player
`standard. Nor is there any interoperability
`between the devices and servers of the various
`
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`

`the delivery of
`
`client entirely controls
`services.
`
` In other words, MPEG DASH offers a
`standards-based approach for enabling a host
`of media services that cable operators and
`telcos have traditionally offered in broadcast
`and IPTV environments and extending those
`capabilities
`to adaptive bitrate delivery,
`including
`live and on-demand content
`delivery, time-shifted services (NDVR, catch-
`up TV), and targeted ad insertion. DASH
`enables these features through a number of
`inherent capabilities, and perhaps most
`importantly, through a flexibility of design
`and
`implementation.
`Its capabilities and
`features include:
`
`• Multiple segment formats (ISO BMFF
`and MPEG-2 TS)
`
`• Codec independence
`
`• Trick mode functionality
`
`• Profiles: restriction of DASH and
`system features (claim & permission)
`
`• Content descriptors for protection,
`accessibility, content rating, and more
`
`• Common encryption (defined by
`ISO/IEC 23001-7)
`
`• Clock drift control for live content
`
`• Metrics for reporting the client session
`experience
`
` A
`
` Tale of Two Containers – MPEG-2 TS and
`ISO BMFF
`
` Under the MPEG DASH standard, the
`media segments can contain any type of
`media data. However, the standard provides
`specific guidance and formats for use with
`two types of segment container formats –
`MPEG-2 Transport Stream (MPEG-2 TS) and
`ISO base media file format (ISO BMFF).
`
`vendors. So, content cannot be re-used and
`creators and equipment makers must develop
`several different versions of their products to
`serve the entire streaming video market,
`greatly driving up costs and restricting the
`market’s overall development.
`
`
`INTRODUCING MPEG DASH:
`A STANDARDS-BASED APPROACH
`
`
` Seeing the need for a universal standard
`for the delivery of adaptive streaming media,
`MPEG decided to step into the void three
`years ago. In April 2009, the organization
`issued a Request for Proposals for an HTTP
`streaming standard. By that July, MPEG had
`received 15 full proposals. In the following
`two years, MPEG developed the specification
`with
`the help of many experts and
`in
`collaboration with other standards groups,
`such as the Third Generation Partnership
`Project (3GPP) and the Open IPTV Forum
`(OIPF).
`
` The resulting MPEG standardization of
`Dynamic Adaptive Streaming over HTTP is
`now simply known as MPEG DASH.
`
` MPEG DASH is not a system, protocol,
`presentation, codec, middleware, or client
`specification. Rather, the new standard is
`more
`like a neutral enabler, aimed at
`providing several formats that foster the
`efficient
`and high-quality delivery of
`streaming media services over the Internet.
`
`ISO/IEC
` As described by document
`23009-1, MPEG DASH can be viewed as an
`amalgamation of
`the
`industry’s
`three
`prominent adaptive streaming protocols –
`Adobe HDS, Apple HLS and Microsoft
`Smooth Streaming. Like
`those
`three
`proprietary platforms, DASH
`is a video
`streaming solution where small chunks of
`video streams/files are requested using HTTP
`and then spliced together by the client. The
`
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`

`

`MPEG-2 TS is the segment format that HLS
`currently uses, while ISO BMFF (which is
`basically the MPEG-4 format) is what Smooth
`Streaming and HDS currently use.
`
` This mix of the two container formats
`employed by the three commercial platforms
`allows for a relatively easy migration of
`existing adaptive streaming content from the
`proprietary platforms to MPEG DASH. That’s
`because the media segments can often stay the
`same; only the index files must be migrated to
`a different format, which is known as Media
`Presentation Description.
`
`
`Media Presentation Description (MPD) –
`Definition and Overview
`
` At a high level, MPEG DASH works
`nearly the same way as the three other major
`adaptive streaming protocols. DASH presents
`available stream content to the media player
`in a manifest (or index) file – called the Media
`Presentation Description (MPD) – and then
`supports HTTP download of media segments.
`The MPD is analogous to an HLS m3u8 file, a
`Smooth Streaming Manifest file or an HDS
`f4m file. After the MPD is delivered to the
`client, the content – whether it’s video, audio,
`subtitles or other data – is downloaded to
`clients over HTTP as a sequence of files that
`is played back contiguously.
`
`
`Figure 3: Media Presentation Data Model
`(Diagram originally developed by Thomas Stockhammer, Qualcomm)
`
`
`
`
`
`three
`the
`in
`file
` Like a manifest
`commercial platforms, the MPD in MPEG
`DASH describes the content that is available,
`including
`the URL addresses of stream
`chunks,
`byte-ranges,
`different
`bitrates,
`resolutions,
`and
`content
`encryption
`mechanisms. The tasks of choosing which
`adaptive stream bitrate and resolution to play
`
`
`and switching to different bitrate streams
`according
`to
`network
`conditions
`are
`performed by the client (again, similar to the
`other adaptive streaming protocols). In fact,
`DASH does not prescribe any client-specific
`playback
`functionality;
`rather,
`it
`just
`addresses the formatting of the content and
`associated MPDs.
`
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`

` To see what an MPEG DASH MPD file
`looks like compared to an HLS m3u8 file,
`consider the following example. The files
`
`
`contain much of the same information, but
`they are formatted and presented differently.
`
` Figure 4: Comparison of MPEG DASH MPD and HLS m3u8 Files
`
`
`Index.m3u8 (top level m3u8)
`
`#EXTM3U
`#EXT-X-STREAM-INF:PROGRAM- ID=1,BANDWIDTH=291500,RESOLUTION=320x180
`stream1.m3u8
`#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=610560,RESOLUTION=512x288
`stream2.m3u8
`#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=2061700,RESOLUTION=1024x576
`stream3.m3u8
`#EXT-X-STREAM-INF:PROGRAM-ID=1,BANDWIDTH=4659760,RESOLUTION=1280x720
`stream4.m3u8
`
`Index.mpd
`
`<?xml version="1.0" encoding="utf-8"?>
`<MPD
` xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
` xmlns="urn:mpeg:DASH:schema:MPD:2011"
` xsi:schemaLocation="urn:mpeg:DASH:schema:MPD:2011"
` type="static"
` mediaPresentationDuration="PT12M34.041388S"
` minBufferTime="PT10S"
` profiles="urn:mpeg:dash:profile:isoff-live:2011">
`
` <Period>
` <AdaptationSet
` mimeType="audio/mp4"
` segmentAlignment="0"
` lang="eng">
` <SegmentTemplate
` timescale="10000000"
` media="audio_eng=$Bandwidth$-$Time$.dash"
` initialisation=" audio_eng=$Bandwidth$.dash">
` <SegmentTimeline>
` <S t="667333" d="39473889" />
` <S t="40141222" d="40170555" />
`
` ...
`
` <S t="7527647777" d="12766111" />
` </SegmentTimeline>
` </SegmentTemplate>
` <Representation id="audio_eng=96000" bandwidth="96000" codecs="mp4a.40.2"
`audioSamplingRate="44100" />
` </AdaptationSet>
` <AdaptationSet
` mimeType="video/mp4"
` segmentAlignment="true"
` startWithSAP="1"
` lang="eng">
`
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`

`

` <SegmentTemplate
` timescale="10000000"
` media="video=$Bandwidth$-$Time$.dash"
` initialisation="video=$Bandwidth$.dash">
` <SegmentTimeline>
` <S t="0" d="40040000" r="187" />
` <S t="7527520000" d="11678333" />
` </SegmentTimeline>
` </SegmentTemplate>
`
` <Representation id="video=299000" bandwidth="299000" codecs="avc1.42C00D"
`width="320" height="180" />
` <Representation id="video=480000" bandwidth="480000" codecs="avc1.4D401F"
`width="512" height="288" />
` codecs="avc1.4D401F" width="1024" height="576" />
` <Representation id="video=4300000" bandwidth="4300000"
`codecs="avc1.640028" width="1280" height="720" />
` </AdaptationSet>
` </Period>
`</MPD>
`
`
`MPEG DASH’S PRIME CAPABILITIES –
`OVERVIEW
`
`
` As mentioned earlier, MPEG DASH offers
`a great number of capabilities for adaptive
`streaming. This section goes into greater
`detail about many of the prime capabilities.
`
` Codec Independence: Simply put, MPEG
`DASH is audio/video agnostic. As a result,
`the standard can work with media files of
`MPEG-2, MPEG-4, H.264, WebM and
`various other codecs and does not favor one
`codec over another. It also supports both
`multiplexed and unmultiplexed encoded
`content. More
`importantly, DASH will
`support emerging standards, such as HEVC
`(H.265).
`
` Trick Mode Functionality: MPEG DASH
`supports VoD
`trick modes for pausing,
`seeking,
`fast
`forwarding and
`rewinding
`content. For instance, the client may pause or
`stop a Media Presentation.
`
`
`
`
`
`
`
`the client simply stops
`this case,
` In
`requesting Media Segments or parts thereof.
`To resume, the client sends requests to Media
`Segments, starting with the next sub-segment
`after the last requested sub-segment.
`
` DASH’s treatment of trick modes could
`prove to be a major improvement over the
`way
`that
`the
`three existing
`streaming
`protocols handle these on-demand functions
`now.
`
` Profiles: Restriction of DASH and System
`Features (Claim & Permission): MPEG
`DASH defines and allows for the creation of
`various profiles. A profile
`is a set of
`restrictions of media
`formats,
`codecs,
`protection formats, bitrates, resolutions, and
`other aspects of the content. For example, the
`DASH spec defines a profile for ISO BMFF
`basic on-demand.
`
`
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`

`
`
`Figure 5: Describing MPEG DASH Profiles
`(Diagram originally developed by Thomas Stockhammer, Qualcomm)
`
`
`
`
`for Protection,
` Content Descriptors
`Accessibility, Content Rating: MPEG DASH
`offers a flexible set of descriptors for the
`media content that is being streamed. These
`descriptors spell out such elements as the
`rating of the content, the role of various
`components, accessibility
`features, DRM
`methods, camera views, frame packing, and
`the configuration of audio channels, among
`other things.
`
` Common Encryption (defined by ISO/IEC
`23001-7): One of the most important features
`of MPEG DASH is its use of Common
`Encryption, which standardizes signaling for
`what would otherwise be a number of non-
`interoperable, albeit widely used, encryption
`methods. Leveraging this standard, content
`owners or distributors can encrypt
`their
`content just once and then stream it to
`different clients with different DRM license
`systems. As a result, content owners can
`distribute their content freely and widely,
`while service providers can enjoy access to an
`open, interoperable ecosystem of vendors. In
`fact, Common Encryption is also used as the
`
`the
`for Ultraviolet,
`underlying standard
`Digital Entertainment Content Ecosystem’s
`(DECE’s) content authentication system.
`Common Encryption will be discussed in a bit
`more detail later in this paper.
`
` Clock Drift Control for Live Content: In
`MPEG DASH, each media segment can
`include an associated Coordinated Universal
`Time (UTC) time, so that a client can control
`its clock drift and ensure that the encoder and
`decoder remain closely synchronized. Without
`this, a time difference between the encoder
`and decoder could cause the client play-back
`buffer to starve or overflow, due to different
`rates of video delivery and playback.
`
` Metrics for Reporting the Client Session
`Experience: MPEG DASH has a set of well-
`defined quality metrics for tracking the user’s
`session
`experience
`and
`sending
`the
`information back to the server.
`
`
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`

`MULTIPLE DRM METHODS & COMMON
`ENCRYPTION
`
`
` As mentioned earlier, one of MPEG
`DASH’s most important features is its use of
`Common Encryption, which standardizes
`signaling for a number of different, widely
`used
`encryption methods.
`Common
`Encryption (or “CENC”) describes methods
`of standards-based encryption, along with key
`mapping of content to keys. CENC can be
`used by different DRM systems or Key
`Management Servers
`(KMS)
`to enable
`decryption of the same content, even with
`different vendors’ equipment. It works by
`defining a common format for the encryption-
`related metadata required to decrypt the
`protected content. The details of key
`acquisition and storage, rights mapping, and
`compliance rules are not specified in the
`standard and are controlled by the DRM
`server. For example, DRM servers supporting
`Common Encryption will
`identify
`the
`decryption key with a key identifier (KID),
`but will not specify how the DRM server
`should locate or access the decryption key.
`
` Using this standard, content owners or
`distributors can encrypt their content just once
`and then stream it to the various clients with
`their different DRM license systems. Each
`client receives the content decryption keys
`and other required data using its particular
`DRM system. This
`information
`is
`then
`transmitted in the MPD, enabling the client to
`stream the commonly encrypted content from
`the same server.
`
` As a result, content owners can distribute
`their content freely and widely without the
`need for multiple encryptions. At the same
`time, cable operators and other video service
`providers can enjoy access to an open,
`interoperable ecosystem of content producers
`and equipment vendors.
`
`
`USE CASES
`
`
` The MPEG DASH spec supports both
`simple and advanced use cases of dynamic
`adaptive streaming. Moreover, the simple use
`cases can be gradually extended to more
`complex and advanced cases. In this section,
`we’ll detail three such common use cases:
`
` Live and On-Demand Content Delivery:
`MPEG DASH supports the delivery of both
`live and on-demand media content
`to
`subscribers through dynamic adaptive HTTP
`streaming. Like Adobe’s HDS, Apple’s HLS
`and Microsoft’s Smooth Streaming platforms,
`DASH encodes the source video or audio
`content into file segments using a desired
`format. The segments are subsequently hosted
`on a regular HTTP server. Clients then play
`the stream by requesting the segments in a
`profile from a Web server, downloading them
`via HTTP.
`
`in
` MPEG DASH’s great versatility
`supporting both live and on-demand content
`has other benefits as well. For instance, these
`same capabilities also enable video service
`providers to deliver additional time-shifted
`services,
`such as network-based DVR
`(NDVR) and catch-up TV services, as
`explained below.
`
` Time-Shifted Services (NDVR, catch-up
`TV, etc.): MPEG DASH supports the flexible
`delivery of time-shifted services, such as
`NDVRs and catch-up TV. For the enabling of
`time-shifted services, VoD assets, rather than
`live streams, are
`required. VoD assets
`formatted for MPEG DASH can be created
`using a transcoder. Additionally, a device
`commonly referred to as a Catcher can
`“catch” a live TV program and create a VoD
`asset, suitable for streaming after the live
`event. Because the VoD asset can be streamed
`in MPEG DASH in the same manner as the
`live content, the asset can be re-used and
`monetized by the operator.
`
`
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` Targeted Ad Insertion: Wherever there is
`video service, there is usually some kind of
`advertising content to monetize the service.
`‘Traditional” ad insertion methods rely on a
`set of technologies based on the widely used
`protocols for distributing UDP/IP video: ad
`servers, ad splicers, and an ecosystem based
`on zoned ad delivery. But as video delivery
`transport has evolved via the new set of
`adaptive HTTP-based delivery protocols from
`Apple, Microsoft and Adobe, the ad insertion
`ecosystem has had to evolve to employ new,
`targeted
`technologies
`for
`insertion and
`delivery of revenue-generating commercials.
`The difficulty of inserting ads with the three
`existing delivery methods is that the protocols
`don’t support the same ad insertion methods,
`due
`to
`the
`inherent nature of how
`the
`protocols work.
`
` MPEG DASH offers the dramatic potential
`to help enable adaptive bitrate advertising on
`many different types of client devices. DASH
`supports the dynamic insertion of advertising
`content into multimedia streams. In both live
`and on-demand use cases, commercials can be
`inserted either as a period between different
`multimedia periods or as a segment between
`different multimedia segments. As in the case
`with VoD trick modes, this would represent a
`significant improvement over the way that the
`three leading streaming protocols currently
`handle targeted ad insertion.
`
`that DASH
`is worth emphasizing
` It
`supports a network-centric approach to ad
`insertion, as opposed
`to a client-centric
`approach in which the client pre-fetches ads
`and splices them locally based on interactions
`with external ad management systems. In
`DASH, the information about when ads play,
`which ads play, and how ads are delivered is
`transmitted
`through
`the MPD, which
`is
`created and distributed from the network.
`
`PROSPECTS FOR INDUSTRY ADOPTION
`– CATALYSTS & CHALLENGES
`
` With the development, ratification and
`introduction of the MPEG DASH platform,
`MPEG is attempting to rally the technology
`community behind a universal delivery
`standard for adaptive streaming media. Many
`tech companies have already enlisted in the
`effort,
`joining
`the new MPEG DASH
`Promoters Group to drive the broad adoption
`of the standard.
`
` Not surprisingly, equipment vendors and
`content publishers are especially enthusiastic
`about the new standard. For instance, content
`publishers savor the opportunity to produce
`just a single set of media files that could run
`on all DASH-compatible electronics devices.
`
`to MPEG DASH’s success,
` The key
`though, will be the participation of the three
`major proprietary players – Adobe, Apple,
`and Microsoft – that now divvy up the
`adaptive streaming market. While all three
`companies have contributed to the standard,
`their levels of support for DASH vary greatly.
`In particular, Apple’s backing is still in
`question
`because
`of
`the
`competitive
`advantages that its HLS platform stands to
`lose if DASH becomes the universal standard.
`
` Besides such competitive issues, MPEG
`DASH faces potential intellectual property
`rights challenges as well. For example, it is
`still not clear if DASH will be saddled with
`royalty payments and, if so, where those
`royalties might be applied. This section will
`look at the intellectual property rights and
`other issues that may yet bedevil the new
`standard.
`
` Unresolved Intellectual Property Rights
`Issues: In addition to the competitive issues,
`there are
`some unresolved
`intellectual
`property rights issues with MPEG DASH. For
`instance, when companies seek to contribute
`intellectual property to the MPEG standards
`
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`

`Microsoft and Adobe. Apple stands out as one
`of the few major tech players that haven’t
`fully enlisted in the effort yet. So there’s a
`great deal of hope in the industry that MPEG
`DASH could actually bring in all of the major
`players and realize its full market potential.
`
` Yet s