视频:CMAF的主要特点是什么?

观看约翰·甘福特的完整演讲， 102年大. 2019年部署CMAF，在… 流媒体会议视频门户.

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约翰Gainfort: CMAF的主要特点是什么? It allows for unified segments across your different manifest and it offers some improvements with your RAM.

首先，让我们谈谈一些统一的片段. Before, when you were encoding and packaging your content, you had a package for both HLS and DASH. HLS使用MPEG-2 TS容器格式. DASH使用自己的MP4格式. So you would have to have two separate segments and then store both of those segments at the same time.

现在, 与CMAF, you can have the same segment packaged for both HLS and DASH, and you only have to store one segment instead of two. 如果你同时使用HLS和DASH播放器, 现在你可以继续这样做, or you could make a switch for one and be unified across.

Unified segments lower your production costs associated with encoding, packaging, and storage. 这是一个重要的好处. It can significantly improve your CDN cache efficiency, especially for live video streaming. It adds in a foundation to define additional conformance points for content and devices regardless of manifest protocol, and what I like most about this is that it provides common ground for industry cooperation.

It's worth noting that if you are using HLS, you need to specify version 6 and above. 有些玩家喜欢ExoPlayer, HLS, JS Bitmovin, 他们可能不会关心这个版本, 但如果你打算用Safari的话, AVPlayer——所以, anything Apple--they are very strict and they do require that this version be set.

接下来是一些数字版权管理, what CMAF offers with DRM is cross-platform and media format compatibility so right now CMAF will be supported out of the box by AVPlayer, ExoPlayer, 和Safari. 它允许单一编码和加密. 这是因为通用加密.

With CMAF, as I mentioned before, we do not require transmuxing on the client's side. So what we can do now 与CMAF is a single packaging workflow when it comes to DRM, 以及单包出版.

让我们看一些简单的术语. 我将继续讲突出显示的两个. 我们有常见的加密AES-CTR, 我将其称为CENC, 下面是CENC, AES-CBC模式或CBCS.

最大的挑战是CBCS的兼容性. 苹果利用了CBCS，所以苹果采用了FairPlay, and all major browsers are moving forward to supporting CBCS. While CBCS is not working at Firefox right now, however, this is coming in the near future. 它可以在Safari中工作, 它在Chrome中工作, 以及其他一些主流浏览器, 但是Edge也不支持CBCS. 然而, that is going to be changing with their introduction of their new Chromium-based browser that is currently in beta right now. We are expecting that to be released in the next year.

如前所述, CMAF不允许混合音频, so what that means is both audio and video renditions could need to be decrypted and possibly have different decryption keys for both audio and video so you can beef up some of your decryption DRM capabilities.

One major challenge is that open-source player availability is somewhat limited. Currently, Shocka Player does not support Play Ready or FairPlay. HLS-JS目前不支持任何DRM. 然而, we have an open PR with HLS-JS to include Widevine into their platform, but both of these platforms have other people providing, 或者继续努力支持它.

那么现在有什么选择呢? One thing we're pushing for is having two manifests with two fragment encryptions for Widevine. So we're targeting CBCS so we can support Apple, Android, Roku, Chrome 和Safari. But then using CTO--or CENC--to support Firefox and Edge with the goal of moving towards CBCS as more browsers adapt to it. If you're using Android and you need to target older Android devices, you'll need to stick with the CENC because CBCS wasn't introduced until 7.0.

Another option that you also have is you can roll your own to your own workflow for your player, 使用电磁辐射, 或加密媒体扩展. EME was designed to enable the same app and encrypted file SKUs in any browser, 不论基础保障计划为何. You can encrypt once and decrypt in any browser using any of those schemes that you need to use. So for Safari you can use FairPlay; Edge, PlayReady; Chrome and Firefox, Widevine. This enables you to contribute to the community since we're using common formats.

这里有一个快速的支持矩阵. CBCS is supported across the board between FairPlay, PlayReady, and Widevine. 然而, with Edge we're looking at having to wait until their new Chromium-based browser comes out, 对于Firefox来说, 它现在得到了支持, but I couldn't tell you exactly which version started to support it. 对于CENC, 苹果设备，也就是iOS, 你的电视——将不支持点击率, Safari设备也不支持.