netflix 认证_hdmi扩展netflix认证

Scott Bolter, Matthew Lehman, Akshay Garg ¹

斯科特·博特 ( Scott Bolter) ， 马修·雷曼 ( Matthew Lehman) ， 阿克舍 ·加格 ( Akshay Garg) ¹

At Netflix, we take the task of preserving the creative vision of our content all the way to a subscriber TV screen very seriously. This significantly increases the scope of our application integration and certification processes for streaming devices like set-top-boxes (STBs) and TVs. However, given a diverse device ecosystem, scaling this deeper level of validation for each device presents a significant challenge for our certification teams.

在Netflix，我们非常认真地负责将内容的创意保留到用户电视屏幕上。 这极大地扩大了我们对机顶盒(STB)和电视等流媒体设备的应用程序集成和认证过程的范围。 但是，在设备生态系统多样化的情况下，为每个设备扩展更深层次的验证对我们的认证团队提出了重大挑战。

Our first step towards addressing this challenge is to actively engineer the removal of manual and subjective testing approaches across different functional touch points of the Netflix application on a streaming device. In this article we talk about one such functional area, High Definition Multimedia Interface (HDMI), the challenges it brings in relation to Netflix certification on STBs, and our in-house developed automated and objective testing workflows that help us simplify this process.

解决这一挑战的第一步是积极设计消除流媒体设备上Netflix应用程序不同功能接触点上的手动和主观测试方法。 在本文中，我们将讨论一个这样的功能领域：高清多媒体接口( HDMI )，与机顶盒Netflix认证相关的挑战以及我们内部开发的自动化和客观的测试工作流程，这些工作流程可帮助我们简化此过程。

为什么要测试高清多媒体接口(HDMI)？ (Why test High Definition Multimedia Interface (HDMI) ?)

The HDMI spec includes several protocols and capabilities that are key to successfully transmitting audio, video, and other digital messages from source (STB) to sink (display) devices. Some of these capabilities include:

HDMI规范包含几种协议和功能，这些协议和功能是成功将音频，视频和其他数字消息从源(STB)传输到接收器(显示)设备的关键。 其中一些功能包括：

• Extended Display Identification Data (EDID)
  扩展显示标识数据(EDID)
• Audio and Video metadata (Info Frames) to help communicate media formats like multi-channel audio and High Dynamic Range (HDR) video
  音频和视频元数据(信息帧)，以帮助传达媒体格式，例如多通道音频和高动态范围(HDR)视频
• High-Bandwidth Digital Content Protection (HDCP)
  高带宽数字内容保护(HDCP)
• Consumer Electronics Control (CEC)
  消费电子控制(CEC)

A high quality Netflix experience on the STB device depends on the correct implementation of each of these capabilities, so we have a vested interest in thoroughly testing them.

机顶盒设备上高质量的Netflix体验取决于这些功能中每一项的正确实现，因此我们对全面测试它们具有既得利益。

扩展HDMI测试 (Scaling HDMI Testing)

Here are some of the challenges associated with HDMI testing on STBs:

以下是与STB上的HDMI测试相关的一些挑战：

• The need to physically obtain and replicate different home entertainment setups of TVs and Home Theater Systems (HDMI topologies).
  物理上需要获取和复制电视和家庭影院系统(HDMI拓扑)的不同家庭娱乐设置。
• Time spent in manually changing these topologies between and during different tests.
  在不同测试之间以及在不同测试期间手动更改这些拓扑所花费的时间。
• Inconsistent test results due to different device models used in the HDMI topology.
  HDMI拓扑中使用的不同设备型号导致测试结果不一致。
• Subjectivity in test results to accommodate differences in HDMI sink behaviors.
  测试结果的主观性以适应HDMI接收器行为的差异。

To deal with these scaling challenges, we have opted to integrate API-enabled HDMI Signal Analyzers into our test infrastructure. This provides the ability to simulate different HDMI topologies within a test case by leveraging the analyzer’s API.

为了应对这些扩展挑战，我们选择将支持API的HDMI信号分析仪集成到我们的测试基础架构中。 通过利用分析仪的API，可以在测试用例中模拟不同的HDMI拓扑。

Next, we will cover basics of the HDMI protocols highlighted in the previous section and walk through the automation workflows that we have developed to address the related challenges.

接下来，我们将介绍上一节中突出显示的HDMI协议的基础知识，并逐步介绍为应对相关挑战而开发的自动化工作流程。

EDID (EDID)

背景 (Background)

Every HDMI-capable TV transmits its Extended Display Identification Data, or EDID, to the connected HDMI source device (STB). The EDID is the means by which a sink device advertises its supported audio and video capabilities such as the spatial resolution (number of pixels), the temporal resolution (number of frames per second), and the color formats in which these frames of pixels are rendered.

每台具有HDMI功能的电视都将其扩展显示标识数据( EDID )传输到所连接的HDMI源设备(STB)。 EDID是接收设备通告其支持的音频和视频功能的手段，例如空间分辨率(像素数)，时间分辨率(每秒帧数)以及这些像素帧所处的颜色格式呈现。

测试方法 (Testing Approach)

Using an HDMI Analyzer we can advertise the EDID of any HDMI capable sink to a STB device. This allows us to simulate an environment under which the device under test (DUT) i.e. the STB behaves just as it would if it were physically connected to an HDMI sink represented by that EDID. This ability to emulate different HDMI sinks has proven very useful for us, yielding increased automation, objective evaluation and scalability of a number of our test cases. In comparison, previously a tester was tasked to gather many physical HDMI sink devices, plug them into the DUT, validate, and move to the next scenario.

使用HDMI分析器，我们可以将任何具有HDMI功能的接收器的EDID通告给STB设备。 这使我们能够模拟一个环境，在这种环境下，被测设备(DUT)即STB的行为就像在物理上连接到该EDID表示的HDMI接收器时一样。 事实证明，这种模拟不同HDMI接收器的能力对我们非常有用，可以提高我们许多测试用例的自动化程度，客观评估和可扩展性。 相比之下，以前测试人员的任务是收集许多物理HDMI接收器设备，将它们插入DUT，进行验证，然后转移到下一个场景。

测试区域：请求的媒体配置文件验证 (Test Area: Requested Media Profile Validation)

A Netflix capable STB should request accurate media streams from our cloud service for optimal user experience. The media stream format and fidelity to be requested is decided by a combination of the inherent HDMI output capabilities of the STB and that of the connected HDMI topology. For example, an HD-only STB should not request 4K video streams. Likewise, a STB connected to a TV with stereo-only speakers should not request multi-channel Dolby Digital Plus Atmos audio streams. In order to comprehensively test the accuracy of the media streams being requested by the DUT under different HDMI setups, we emulate a variety of HDMI sinks with distinct resolution and media format capabilities by looping through a collection of EDID files on an HDMI analyzer connected to the DUT. For each EDID version we then validate the media profiles being requested by the DUT in an automated manner by comparing them against a reference expected set. This ensures that the media streams requested by DUT accurately reflect its HDMI capabilities and the active HDMI topology.

具有Netflix功能的机顶盒应从我们的云服务中请求准确的媒体流，以获得最佳的用户体验。 所需的媒体流格式和保真度由机顶盒固有的HDMI输出功能和所连接的HDMI拓扑的固有输出能力共同决定。 例如，纯高清机顶盒不应请求4K视频流。 同样，连接到带有立体声扬声器的电视的STB不应请求多声道Dolby Digital Plus Atmos音频流。 为了全面测试DUT在不同HDMI设置下请求的媒体流的准确性，我们通过在连接至HDMI的HDMI分析仪上循环浏览EDID文件的集合，来模拟各种具有不同分辨率和媒体格式功能的HDMI接收器。 DUT。 然后，对于每个EDID版本，我们通过将其与参考预期集进行比较，以自动化的方式验证DUT所请求的媒体配置文件。 这可确保DUT要求的媒体流准确反映其HDMI功能和活动的HDMI拓扑。

高动态范围 (HDR)

背景 (Background)

HDR enables a wider range of colors, deeper blacks, and brighter specular highlights. However, when graphics in the sRGB color space, such as subtitles and media player controls, are composited on a video layer in the HDR format they need to be correctly converted into a wider BT.2020 color space and a larger range of luminance. Netflix gives guidance to preserve the original creative intent of the non-HDR graphics, so they appear the same when rendered in HDR output mode. This concept is known as perceptual mapping (BT.2087.0).

HDR可实现更广泛的颜色范围，更深的黑色和更亮的镜面反射高光。 但是，当sRGB色彩空间中的图形(例如字幕和媒体播放器控件)以HDR格式合成在视频层上时，需要将它们正确转换为更宽的BT.2020色彩空间和更大的亮度范围。 Netflix提供了指导，以保留非HDR图形的原始创意意图，因此在HDR输出模式下呈现时，它们看起来是相同的。 这个概念称为感知映射( BT.2087.0 )。

An increasing number of STB devices are capable of producing HDR output within the entire user experience rather than only during video playback, making accurate graphics color space and luminance mapping a more important part of a good user experience. Incorrectly mapped, these graphics can appear dim or colors can look oversaturated as you can see in the images below.

越来越多的STB设备能够在整个用户体验中而不是仅在视频播放过程中产生HDR输出，从而使准确的图形色彩空间和亮度映射成为良好用户体验中更为重要的部分。 如您在下图中所看到的，映射不正确时，这些图形可能显示为暗淡或颜色看起来过饱和。

测试方法 (Testing Approach)

Even if a STB follows the Netflix recommended sRGB to HDR color volume mapping for graphics, the end result on a screen is rather subjective. Different display panels add their own characteristics to the final output. Some testers might even prefer oversaturated graphics. Thankfully we can use an HDMI analyzer in an automated manner to remove this subjectivity from our testing.

即使机顶盒遵循Netflix建议的图形从sRGB到HDR的颜色体积映射，屏幕上的最终结果还是相当主观的。 不同的显示面板在最终输出中添加了自己的特性。 一些测试人员甚至可能更喜欢过饱和的图形。 值得庆幸的是，我们可以自动使用HDMI分析仪来消除测试的主观性。

测试区域：sRGB图形到HDR色彩体积的映射 (Test Area: sRGB Graphics to HDR Color Volume mapping)

Using an HDMI Analyzer we can objectively measure the pixel values for characteristics such as chromaticity and luminance. In our HDR-specific tests we use graphics that cover both the boundary of the sRGB color space as well as its entire luminance range. When these images are then applied to the graphics plane of a STB sending HDMI output in HDR mode, the STB has to convert its graphics plane into HDR color volume so that it can output both the graphics and video elements in a unified format. By capturing this STB output on an HDMI analyzer we measure and verify that after this graphics color volume conversion on the STB, the output pixel values of the graphics section follow the expected boundaries of it’s original non-HDR color space and luminance range as per our perceptual mapping requirement. The figure below highlights this testing process.

使用HDMI分析仪，我们可以客观地测量像素值的色度和亮度等特性。 在特定于HDR的测试中，我们使用覆盖sRGB色彩空间边界及其整个亮度范围的图形。 然后，当将这些图像应用于以HDR模式发送HDMI输出的STB的图形平面时，STB必须将其图形平面转换为HDR色彩量，以便它可以以统一格式输出图形和视频元素。 通过在HDMI分析仪上捕获此STB输出，我们测量并验证了在STB上进行图形颜色量转换之后，图形部分的输出像素值遵循其原始非HDR颜色空间和亮度范围的预期边界，具体取决于我们感知映射要求。 下图突出显示了此测试过程。

HDCP (HDCP)

背景 (Background)

With the goal of preventing content piracy, it is of utmost importance that a STB device running the Netflix application is able to protect our content from being compromised on that device. One of the many important steps toward ensuring this is to validate STB devices’ adherence to High-bandwidth Digital Content Protection (HDCP) policies as specified in the Digital Rights Management (DRM) licenses associated with our streams.

为了防止内容盗版，运行Netflix应用程序的STB设备能够保护我们的内容不受该设备的损害是至关重要的。 确保这一点的许多重要步骤之一就是验证STB设备是否遵守与我们的流相关联的数字版权管理(DRM)许可证中指定的高带宽数字内容保护( HDCP )策略。

A Netflix DRM license typically provides a mapping of the minimum required HDCP version (v1.4 or v2.2) for each content resolution i.e. the minimum HDCP version that must be established on the link between HDMI source (STB) and sink device (display) for the source to be able to send the associated decrypted video signal at a specific resolution over the HDMI cable. In order to effectively apply these HDCP policies, we must be able to trust the HDMI source device’s reporting of the effective HDCP state negotiated with the HDMI sink as well as its enforcement of the minimum required HDCP version for each output content resolution.

Netflix DRM许可证通常为每个内容分辨率提供最低要求的HDCP版本(v1.4或v2.2)的映射，即必须在HDMI源(STB)和接收器设备(显示器)之间的链接上建立的最低HDCP版本。 )，以便该源能够通过HDMI电缆以特定的分辨率发送相关的解密视频信号。 为了有效地应用这些HDCP策略，我们必须能够信任HDMI源设备对与HDMI接收器协商的有效HDCP状态的报告，以及其对每种输出内容分辨率所要求的最低HDCP版本的实施。

测试方法 (Testing Approach)

As the task of procuring various audio/video repeaters (e.g. Home Theater Systems), HDMI switches and connected displays is very time-consuming and does not scale, once again we lean in on using an HDMI analyzer for our test automation purposes.

由于采购各种音频/视频中继器(例如家庭影院系统)，HDMI开关和所连接的显示器的任务非常耗时且无法扩展，因此，我们再次倾向于使用HDMI分析仪来实现自动化测试。

测试区域：准确的HDCP版本报告 (Test Area: Accurate HDCP Version Reporting)

Leveraging the analyzer, we can simulate the following HDMI topologies:

利用分析仪，我们可以模拟以下HDMI拓扑：

1. STB connected to a TV
   STB连接到电视
2. STB connected to a repeater which in turn is connected to a TV
   STB连接到中继器，中继器又连接到电视

In each topology, we can also tweak the level of HDCP support i.e. HDCP v1.4 or HDCP v2.2 on the repeater and the TV individually in an automated manner using the relevant HDMI Analyzer API’s. These abilities allow us to create multiple test setups as shown in the figure below and in each such setup, the DUT is required to report the effective HDCP version (the lowest version in the topology) to the Netflix application so that our service can serve the appropriate content to the client in that configuration.

在每种拓扑中，我们还可以使用相关的HDMI分析器API以自动化的方式分别调整转发器和电视上的HDCP支持级别，即HDCP v1.4或HDCP v2.2。 这些功能使我们能够创建多个测试设置，如下图所示，在每个这样的设置中，DUT都必须向Netflix应用程序报告有效的HDCP版本(拓扑中的最低版本)，以便我们的服务可以为在该配置中向客户端提供适当的内容。

测试领​​域：遵守HDCP政策 (Test Area: Adherence to HDCP Policies)

While testing of the reported HDCP version would ensure that the DUT sends correct data to Netflix services to obtain the appropriate content streams and DRM licenses, we also need to test that the DUT adheres to the video output restrictions stipulated in that license e.g. blocking content requiring HDCP v2.2 when HDCP v1.4 is negotiated on the HDMI link. To ensure this we use an HDMI analyzer to emulate different HDMI topologies virtually and initiate playback using a variety of DRM licenses that stipulate distinct types of content protection rules for video output. Finally, we switch across different HDCP versions on the HDMI Analyzer, ensuring that in each configuration, DUT is able to follow the DRM license stipulated video output protection rules by taking one of the following required actions:

虽然测试报告的HDCP版本将确保DUT向Netflix服务发送正确的数据以获得适当的内容流和DRM许可证，但我们还需要测试DUT是否遵守该许可证中规定的视频输出限制，例如阻止要求在HDMI链路上协商HDCP v1.4时的HDCP v2.2。 为了确保这一点，我们使用HDMI分析器虚拟地模拟不同的HDMI拓扑，并使用各种DRM许可证启动播放，这些许可证规定了视频输出的不同类型的内容保护规则。 最后，我们在HDMI分析仪上切换不同的HDCP版本，以确保在每种配置中，DUT都能通过采取以下必要措施之一来遵循DRM许可规定的视频输出保护规则：

1. Allow HDMI output of the video stream as-is
   允许HDMI流直接输出视频流
2. Downscale the video output resolution if resolution is the content protection criteria
   如果分辨率是内容保护标准，则降低视频输出分辨率
3. Block the HDMI video output completely
   完全阻止HDMI视频输出
4. Stop playback by throwing an insufficient HDCP protection error to Netflix application
   通过向Netflix应用程序抛出不足的HDCP保护错误来停止播放

each of which can be validated in an automated manner leveraging the HDMI analyzer and the relevant Netflix application events.

利用HDMI分析仪和相关的Netflix应用程序事件，可以自动验证每一项。

CEC (CEC)

背景 (Background)

Consumer Electronics Control (CEC) protocol implementations on HDMI devices typically provide a convenience of an indirect device control e.g. using a TV remote to control the volume of the connected home theater system. However, aside from this benefit, CEC messages can also indicate which HDMI input of a downstream device (HDMI sink) is actively being used or if the downstream device itself is in a standby state. This is something of interest to a streaming application like Netflix running on an HDMI source. Whether or not the STB running Netflix is connected to an active HDMI input on the sink device has implications for what the Netflix application should or should not be doing, so we want the STB to correctly signal this active or inactive CEC state to the Netflix application.

HDMI设备上的消费电子控制(CEC)协议实现通常可提供间接设备控制的便利，例如使用电视遥控器控制连接的家庭影院系统的音量。 但是，除此好处外，CEC消息还可以指示下游设备(HDMI接收器)的哪个HDMI输入正在使用中，或者下游设备本身是否处于待机状态。 这是运行在HDMI源上的诸如Netflix之类的流应用程序所感兴趣的。 运行Netflix的STB是否已连接到接收设备上的活动HDMI输入是否影响Netflix应用程序应做的事情，因此我们希望STB向Netflix应用正确发送此活动或非活动CEC状态的信号。

测试方法 (Testing Approach)

In order to remove the issues of variability in how CEC is branded on a sink device, how it is enabled in a device menu system, and under what conditions relevant CEC messages are transmitted, we use an HDMI analyzer to send carefully crafted CEC operational codes to the STB.

为了消除CEC在接收器设备上的商标方式，如何在设备菜单系统中启用它以及在什么条件下发送相关CEC消息方面的可变性问题，我们使用HDMI分析仪发送精心制作的CEC操作代码到机顶盒。

测试区域：准确的CEC活动状态通知 (Test Area: Accurate CEC Active State Notifications)

After sending custom CEC messages targeted to the DUT on the HDMI bus, we can ensure that it behaves correctly in response to these messages, in terms of its CEC active state notification to the Netflix application. Some of these test scenarios are highlighted in the figure below.

在HDMI总线上发送针对DUT的自定义CEC消息后，根据向Netflix应用程序发出的CEC活动状态通知，我们可以确保其对这些消息做出正确的响应。 下图中突出显示了其中一些测试方案。

As an example we could send a CEC message to the STB to notify it that the active HDMI input on the HDMI sink has changed to some other source. Likewise we can also simulate the occurrence of an HDMI sink standby transition by broadcasting a CEC Standby message. In both scenarios we expect the source device to become CEC inactive and notify this updated CEC state to its local Netflix application.

例如，我们可以向STB发送一条CEC消息，通知它HDMI接收器上的活动HDMI输入已更改为其他来源。 同样，我们还可以通过广播CEC Standby消息来模拟HDMI接收器待机过渡的发生。 在这两种情况下，我们都希望源设备变为非活动CEC状态，并将此更新的CEC状态通知其本地Netflix应用程序。

摘要 (Summary)

At Netflix we deeply care about the quality of experience for our subscribers. It motivates us to invest in test automation to scale our approach to ensure the best possible device integration from our partners. The ideas discussed here represent a tip of the iceberg with many more challenges still left to be identified and addressed. If you are passionate about device test automation and want to help us solve these kinds of problems, please check out our jobs site for exciting opportunities.

在Netflix，我们深切关注订户的体验质量。 它激励我们投资于测试自动化，以扩展我们的方法，以确保我们的合作伙伴能够实现最佳的设备集成。 这里讨论的想法代表了冰山一角，还有许多尚待确定和解决的挑战。 如果您对设备测试自动化充满热情，并希望帮助我们解决此类问题，请访问我们的工作网站以获得令人兴奋的机会。

[1] Equal contribution from all authors.

[1]所有作者平等贡献。

[2] Diagrams courtesy of Sunny Kong.

[2]图表由Sunny Kong提供 。