观点:编解码器之战将在我们的未来上演吗?
Today, the industry is abuzz with 文章, claims, and counterclaims about 编解码器. 作为一个一直沉浸在 MPEG 从成立之日起, I want to explain the history of 编解码器 in order to give you a better understanding of where the market is headed.
直到现在, video standards have been necessary to create an interoperable world for the distribution of media, initially for broadcast given the constraints of hardware decoders and later on for unicast as the industry evolved toward software-based decoding. The first bump on the MPEG road came in the early 2000s when 微软 developed its own codec, VC9, 后来被SMPTE称为VC-1.
有人想知道VC-1发生了什么吗? 这个编解码器的性能与 mpeg - 4 AVC / H.264 and roughly the same licensing terms, so the industry response was “Thanks, but no thanks.” The second bump in the road came in 2010 when Google bought On2 to gain access to the A/V codec technology. 他们推出了VP8，仅限于YouTube，现在正在过渡到 VP9. 到目前为止, VP8/9在YouTube之外取得的成功非常有限, 而且它在移动设备上也不被广泛支持. 谷歌这样的公司, 微软, 思科, 和Mozilla不喜欢HEVC的MPEG许可模式, 因为还不清楚, 所以他们创造了 开放媒体联盟(AOM) 提供… 开源，免版税的编解码器 效率是HEVC的两倍. 这很有说服力，对吧?
现在我们来做一些数学运算. 付费电视市场价值约为3500亿美元, OTT市场的价值约为350亿美元. 即使一个新的编解码器能够解决OTT市场, 这一点还有待证实, 它仍然需要在一个比中国大10倍的市场取得成功. 事实上， AV1, AOM新编解码器, is only targeting OTT delivery and will not be able to solve the codec problems for the broadcast market.
让我们来看看广播方面的重大挑战. If service providers want to increase the resolution of their channels from SD to HD in emerging countries and HD to UHD in developed regions, 特别是在DTT等带宽有限的网络上传输, 移动, 或OTT (DSL), 那么2020年以后就需要一个新的编解码器了.
这让我们看到了开源编解码器的动态特性. The nature of an open source codec is that it will be updated on a regular basis. 作为参考，新版本的 参考设计套件(RDK)是开源电缆中间件，每月发布一次. There will be multiple versions of AV1 operated by different OTT services that will have to interoperate with billions of AOM-capable devices. 谁来当交警? AOM很可能会定义互操作性概要文件, 而是基于我们所看到的DASH, it may be several years until there is a good level of interoperability for live services.
OTT运营商推动AOM (i).e., 网飞公司, Amazon) will have to impose strict device rules and duplicate streams on their servers, 产生额外的编码和存储成本. This scenario could work for VOD where the library size is limited, but what about live applications? This would require using unicast to stream multiple versions to address each different client. If the operator has a managed network where multicast is used for live, 没有足够的网络容量进行联播.
这就引出了一个问题:AOM是直播OTT的真正解决方案吗? Well, if you liked the fragmentation of Android, you are going to love AOM. 开源编解码器可以在软件客户端环境中工作, 例如PC上的web浏览器, 但不能在电视上使用, IP机顶盒, HDMI软件狗, 智能手机, 或者游戏站. 本质上, it is not compatible with the lion’s share of OTT clients with a dedicated hardware decoder for achieving a very high performance target (i.e., games and video in Ultra HD), a low cost (IP STB) or power efficiency (i.e.，流动装置).
mpeg - 4 AVC / H.自2002年以来，264已成为国际标准. And while MPEG-4 encoders have been deployed for at least 10 years all over the world, some TVs today have a hard time decoding a standard stream that is ratified for 14 years. Since most of those TVs are not connected, only an over-the-air update can be done. 这需要花钱，而且并非所有国家都能做到. 想象一下，如果编解码器每个月都在变化. 你觉得这样行吗?
现在让我们回到AOM的AV1编解码器. Before it can be successful, performance claims have to be substantiated. MPEG is working with engineers to reach a factor two compression at the codec level by 2020 as an international standard, 这意味着它的能力将在2019年得到展示.
关于AV1的免版税方面, MPEG has developed a lot of essential patents for block-based compression. 除非AOM发明了一种全新的技术, 它将不得不向MPEG专利持有者支付费用, who are not making much money with HEVC these days and will be eager to monetize on AV1.
最后但并非最不重要的, 重要的是要注意AV1只关注编解码器级别, 而MPEG则侧重于系统级. Harmonic believes (and recently made a contribution to MPEG) that if we work at the system level, we could reach a factor four compared with the HEVC approach of using new techniques such as elastic encoding, 基于OTT内容的速率控制, VR平铺, 可扩展的8K编码, 前后处理配对, 机器学习, 等. 当然, 如果考虑到所有因素, then the chances to reach a factor four are higher as opposed to the simple broadcast of HD. Those techniques will bring major differences compared with the pure codec rat race. 除了, they will solve system problems such a picture quality and latency that could derail applications delivered over the internet if performance levels are not met.
简而言之, MPEG具有通过系统方法超越AOM的潜力, coming only two years after AV1 was deployed on web browsers for wired applications. What’s more, it’s a platform that also addresses the broadcast market.
你可以说，AOM推动了英特尔(Intel)等芯片公司的反弹, 手臂, AMD和nvidia, 这些公司都在为个人电脑和移动设备开发硅技术. 但是在移动设备上, the A/V decoding function is always done in the hardware for cost and power reasons. 用于AV1解码的逻辑必须重新编程, 可能使用了类似的技术 FPGA. (参见英特尔最近对Altera的收购.)这还没有部署, 当然，今天适用于高清的可能不适用于超高清, 尤其是像WCG这样的好东西, HDR, HFR和NGA在2017年增加!
AOM到底给市场带来了什么呢? It offers a clear alternative for the web world that does not want to pay an "MPEG tax," a potential plan B if HEVC licensing does not get resolved and possibly new algorithm innovation that is less controlled than MPEG.
Will the content providers and consumers win at the end of this codec war? MPEG还没有完成. 它要么创新，要么变得无关紧要, 尤其是在授权条款越来越不被接受的情况下. MPEG会从HEVC中吸取教训吗? Trust me, there is a lot of frustration in the MPEG community, and they won’t repeat past mistakes.
蒂埃里·福蒂埃是v谐波视频策略副总裁. 这是一篇由供应商提供的文章. StreamingMedia.com accepts contributions from vendors based solely on the 信息 and insight they offer our readers.
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