OTT Delivery: Creating Strategies for Video Streaming
“Over the top”(OTT)是我们这个行业中最被滥用、最模棱两可的流行语之一.
In order to understand linear video delivery in OTT models, 第一个, you have to look at what OTT means outside of video. To mobile operators, OTT is a scary proposition. 调用, 短信, 到目前为止，图像信息一直完全在运营商的控制之下, and therefore presented an opportunity for revenue. For those operators, OTT服务几乎是智能手机需要开放互联网接入的一个不可避免的症状, 并带来了许多与运营商传统收入模式相竞争的服务. King of all these is 天空pe, and it provides a clear example of what “top” the service comes “over” to earn the moniker OTT: Namely the pay wall that is the per-minute billing system of the mobile operator.
In exactly the same way I often dogmatically emphasize that “cloud” is an economic term defining the move of CAPEX to OPEX when building IT infrastructure, OTT is also an economic term 第一个 and foremost. 在最好的情况下, it means that the operators are able to derive data transit and bandwidth-oriented revenues for the delivery of network service on behalf of providers who otherwise charge much higher premiums to end users or sponsors. 在最坏的情况下, 运营商在数据传输方面处于亏损领先地位，以鼓励用户留在他们那里，而不是把业务交给其他运营商. 一直以来, OTT服务从网络运营商的用户那里获得收入，而(不一定)与网络运营商分享任何收入.
然而, with this economic common denominator noted, in any specific technical context the term OTT has a range of implementation models that ensure that the cost of this data transit and bandwidth delivery itself is as profitable as possible for the network operator, 利润是否以运营商CDN收入或用户留存率来衡量.
因此, 一组以运营商为中心的广播OTT模式，用于日益连接的电视市场，通常使用用户isp提供OTT服务. 为了这个社区, OTT evokes a tight coupling of application control, typically embedded securely in smart TVs or set-top boxes, with a primary content origination strategy.
这 typically results in a streaming video-based workflow connecting content publishing sources with points of distribution in some form of content management system. 这, 反过来, 是否与最终用户场所中的应用程序同步, 并以某种形式的电子节目指南或其他用户界面的形式呈现在他们的设备上.
广播OTT提供商与运营商cdn密切合作，以确保管理良好的IP网络的服务质量, and they will work in regions. 这 is result of these operator CDN relationships, 以及现有电视内容版权模式造成的市场塑造.
For example, in the U.K.，我们看到 英国广播公司 (iPlayer), 天空 (天空NOW), BT (BTSport/BT Vision)是常见OTT主张的主要例子. While the content originates in a form that is delivered directly to the internet for general-purpose access through a device of the consumer’s choosing, 这些出版商也都非常努力地向联网电视和机顶盒提供自己的服务. 这就产生了免费的view、YouView、BT Vision和Virgin Media在美国的机顶盒.K., with internet connections, that can access 英国广播公司 iPlayer, 或天空 Now, 这些服务通常与YouTube等其他OTT提供商一起出现, Netflix和Vimeo.
There is a key separation between simple streaming applications that the device can browse and the broadcast OTT providers -- the broadcast OTT provider’s services will appear ‘integrated’ with traditional broadcast TV, YouTube和Netflix等服务将成为完全独立的应用程序.
An example: A typical user might see TV, YouTube, and Netflix options on her main connected TV menu, 但可能不会将英国广播公司 iPlayer视为一个独立的菜单应用程序. 然而, 传统的英国广播公司1线性电视广播可能包括扩展功能, 比如红色按钮, 网络硬盘录像机, pause and rewind live, or extended on demand viewing catalogues, perhaps related to the current broadcast. 所有这些都是通过英国广播公司与广播OTT提供商的应用程序的紧密整合而实现的，该应用程序实际上是终端设备上的本机.
这 native capability is brought about by the device manufacturers’ adoption of various “standard” OTT models that have formed within different schools and layers of the broadcast industry as it has worked out how to adopt IP in its distribution workflow.
Some examples of this are the U.K.’s Digital Television Groups’ D-Book standard, 以及YouView和HbbTV的倡议，以及开放IPTV论坛. 每个协议都列出了设备应该如何响应通过无线传输的应用程序的参数, 给予那些能够提供此类应用程序的人独家接触和能力，以获得额外的收入或价值.
In the D-Book/免费的view Plus model, MHEG(多媒体和超媒体专家组)应用程序与数字电视信号一起播出, and is received and decoded by the device, 反过来，通过使用设备的互联网连接来获取和播放流媒体，响应用户提出的任何流媒体内容请求. 因为该应用程序仅对广播占用空间中的应用程序可用, the users of the service are limited to that footprint too.
这意味着覆盖相同足迹的ISP成为广播OTT提供商内容交付网络的绝佳候选, and a direct connection from the broadcast OTT provider’s content aggregation and origination point effectively means that the broadcast OTT provider is delivering content directly to the end user. 再一次。, 广播OTT平台与特定网络运营商之间的合作是很常见的, 如果不是必要的.
相比之下，YouTube和Netflix是用户激活的应用程序. 这些需要专门针对设备的本地中间件进行编码，并且可能只是设备的互联网浏览功能的扩展. 内容通过最终用户的ISP从YouTube或Netflix CDN传送到最终用户. 虽然这简化了YouTube和Netflix的发布(他们不需要为每个运营商建立新的交付工作流程), 缺乏与终端设备的紧密集成限制了他们提供某些广播友好的高级功能, 例如覆盖在广播服务上的红色按钮服务.
因此，这种应用程序“付费墙”仍然存在，并为广播公司增加价值和维持其订户收入划定了保护边界.
The Taxonomy of OTT Video
如你所见, OTT的定义实际上取决于服务在哪里收费, rather than on any specific technical strategy.
Netflix和YouTube经常被认为是典型的OTT服务, 它们实际上只代表一种类型:本文的目的是“纯OTT”, 将它们与上面讨论的更紧密地集成工作流的广播OTT模型区分开来.
更进一步，我们可以像这样松散地分组不同的模型:
数字地面电视(德勤)/直接到家(DTH)卫星运营商. 运营商可以使用德勤或DTH系统来提供传统的广播服务. 他们可能会也可能不会在这些私人管理的网络上使用IP, 并且需要特定的消费设备/机顶盒连接到这些网络. The OTT application control (MHEG/ EPG data, etc.)需要作为广播传输的一部分通过(通常是非ip的)广播网络传输. (The red button trigger is sent in the broadcast stream.)
IPTV运营商. 实际上，这些是具有QoS控制的用户电路的isp，端到端管理IP. 消费者将不得不订阅她的网络服务来接收IPTV包, 它们都有一个特定的机顶盒和一个特定的接入电路.
Broadcast OTT operators. 这些类似于传统的德勤/DTH多业务运营商, 尽管他们完全在IP领域工作，他们将交付责任交给他们自己的运营商CDN和接入网, or third-party ISP subscriber networks. They target specific devices and often tightly integrate with the existing 德勤/DTH and telco services to provide the OTT services as value added extensions of the existing 德勤/DTH broadcasts. 而付费墙可能存在于广播OTT运营商, 合作伙伴德勤/DTH和电信网络往往有直接的商业关系, even if that only extends to providing access to the set-top boxes with EPG and UI support (although it may extend to a near-IPTV like distribution model too).
Pureplay OTT Operators. 这些完全不同于接入网和应用层的交付. In reality the very large players such as YouTube and Netflix will work closely with connected TV and set-top box vendors to provide native optimized applications closer to the broadcast OTT model, although there are many PC-based set-top boxes on the market that can access Netflix and YouTube APIs and display the content in their local browsers as if there was a native application. 纯粹的OTT运营商可能不会与广播网络运营商发展关系, leaving the content distribution to partner pureplay CDNs. One thing they do share, and which defines them as pure play OTT operators, is that they do not have end-to-end QoS guarantees. 在这方面，它们在技术上与今天在网络上发现的传统流媒体服务没有什么区别.
These models are all shown on the topology schematic in 图1.
我想强调几个关键的事情，我试图在这个图表中表示.
灰色圆圈表示到达终端用户的物理广播接入网. A subscriber who is connected to this wired physical network layer (which may well not be IP based) can connect through that physical layer to the cable TV broadcast signals. Consumers with IP access are able to reach the operator CDN, IPTV业务, and potentially third-party pureplay OTT services.
蓝圈勾勒出广播运营商的运营网络, 在哪里准备内容并将其分发到物理接入网络.
The small green circle shows a third-party telecoms (or cable) network which provides the end user with internet access through an ISP who is neither involved in the OTT services nor the broadcast services.
请注意，在右上角，德勤和DTH广播公司可以使用没有物理连接到最终用户的广播网络. 诸如此类的广播模型不提供本机返回路径, which is critical for IP-based OTT services. 对于德勤和DTH，这意味着必须为最终用户提供单独的互联网连接, typically by ADSL or FTTH, 这可能会或可能不会与OTT服务订阅捆绑在一起(绿色或灰色和蓝色圆圈).
Within and between the blue and gray circles, operators can control QoS, 这些圆的周长表示控制结束的边界.
橙色圆圈代表互联网，例如，纯CDN可能在其中运行. The edges of that CDN network might offer public internet peering (shown as the red route) or private peering and transit connectivity (the yellow route), and this direct connection to the broadcast operator’s physical IP network could provide a QoS managed environment from the CDN hand-off forward to the end user.
这 topology does not allow for guaranteed end-to-end QoS, since the CDN only offers a best-effort SLA. 反过来，纯OTT提供商只能将“改进的”QoS传递给广播公司. The typical approach to the non-QoS regions between the CDN and the ISPs or operator networks is to provision significant extra capacity in interconnects and peering and cross their fingers -- and to be honest this model works very well.
然而，当商业合同落实到位时，这种做法通常不被看好. 因此, 运营商和内容提供商之间的私人链接通常是出于问责原因而不是技术原因而创建的. 这可能导致某些OTT提供商与广播运营商密切合作, such as Netflix arranged with Comcast in the U.S.
这 model is shown as the yellow line. It represents a service such as Netflix as an augmented service to IPTV (light blue) generated inside Virgin Media and delivered over their network with QoS guaranteed end to end, or even simply to the traditional cable, 德勤, 或者是对广播运营商来说操作开销很小的DTH服务, 除了向Netflix收取地区运营商CDN分销的费用，作为其核心广播订阅的增量收入. 在这个模型中, 最终用户可以直接订阅Netflix，作为他们基本广播套餐订阅的额外费用.
当然, 像YouTube或英国广播公司 iPlayer这样的免费内容不需要终端用户付费订阅. 在这种情况下，运营商CDN成本可能被认为是OTT提供商的亏本业务, 因此，YouTube或英国广播公司可能会选择通过公共互联网模式，将其面向网络的流媒体内容扩展到维珍媒体机顶盒的观众. 这 approach avoids becoming relying on the operator CDN.
这 tends to create a more level co-dependent playing field for both parties: The operator CDN might opt to internally bear the cost of bringing the content to the EPG, so that the pureplay OTT services can be browsed. 这就像在机顶盒的浏览器中支持OTT服务一样简单. 广播OTT提供商必须进行投资才能做到这一点, 但纯OTT提供商的内容是必须的，他们不能在不流失用户的情况下将其排除在套餐之外.
在这种情况下, the cost of network transit between the pureplay OTT providers’ CDN edge and the end user (shown in my diagram in red) is free to the broadcast network if it is delivered by the pureplay OTT operator and distributed through the end user’s chosen ISP. 这是最低的QoS SLA，因此也是最便宜的OTT模型, but it is also usually good enough for most consumers.
At the other end of the spectrum, 紫色ip编码视频可以直接从运营商网络发送到广播接入网和, so long as the end user is “on net,” then QoS can be guaranteed. 这 would classify the IP delivered video as being IPTV; it is interesting to note that the same video delivered via a third-party ISP would change the terminology from IPTV to OTT, 这种QoS差异经常被(有疑问地)引用为我们在定义OTT时所跨越的墙, 导致许多人认为OTT的质量不如IPTV或广播.
最后, point A shows a critical interface where the MHEG app, 或类似的EPG细节，宣布在传统广播网络上存在任何OTT内容, 建立了.
这 thin brown line (seen by marker A in the head end) represents metadata and small application data that is distributed over the broadcast network to facilitate access to the broadcaster OTT content. 它是传统广播节目的一部分, 这将这些服务与广播网络运营商之间的关系联系起来, the broadcast OTT operators, and the content providers. 这种亲密关系创造了商业控制，并为所有各方带来了收入, something that pureplay OTT services often do not do.
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