苹果加入开放媒体联盟:意味着什么?

On January 5 , roughly 27 months after the inception of the Alliance for Open Media (AOM), 苹果公司在该组织的网站上以“创始成员”的身份出现.“和其他人一样，我们第一次读到这个故事是在 CNET, and CNET likely found out when the Alliance simply updated its website. As you probably know, AOM成立于2015年9月, 在HEVC皇室疯狂的高峰期, to consolidate the development of multiple open-source codecs into one. 这个编解码器叫做AV1，而比特流是 计划于2018年初冻结.

显而易见的问题是，苹果为什么要加入这个组织, and how do we expect Apple to deploy AV1 and possibly other codecs like VP9? 我们将在暂停思考后按顺序解决这些问题.

网络视频到底发生了什么

When Adobe added H.264 to Flash in 2007, Adobe开发者Tinic Uro写了一篇标志性的博客文章, since taken down, 名为“网络视频到底发生了什么”." Within 2 or 3 months or so, computer-based streaming, 这几乎是当时所有的东西, pivoted from On2's VP6, the ironic predecessor to AV1, to H.264, from which HEVC was born.

所以我要打断乌罗的电话，问“刚刚发生了什么事??“从哲学的角度来看，苹果的举动是结构性的. 至于对编解码器市场的影响，还有待观察.

哲学背景是这样的. Google purchased On2 for $120 million or so and released VP8 as an open-source codec in May 2010. 苹果对H.264, with support in QuickTime and various devices, and was a licensor in the MPEG LA H.264 (and HEVC) patent pools.

One of the first reviews of VP8's source code was by Jason Garrett-Glaser (then a third-year college student also known as Dark Shikari) who was (is) one of the developers of the x264 codec. His review, also since taken down, was extremely critical from both technical and intellectual property (IP) perspectives. For example, he stated “VP8，作为一个规格，应该比H好一点.264基线配置文件和VC-1. 它甚至不能与H竞争.264 Main or High Profile." Regarding IP, he also stated “VP8和H太相似了.264: a pithy, if slightly inaccurate, description of VP8 would be 'H.264基线配置文件与更好的熵编码器.' Though I am not a lawyer, 我简直不能相信他们能逃脱惩罚, 尤其是在当今这个诉讼泛滥的时代."

When asked what he thought about VP8, Apple's Steve Jobs, responding in a 4:30 a.m. email from his iPhone, 只是提供了加勒特-格拉泽评论的链接, 他说:“本质上是数字化的。.换句话说:糟糕的编解码器，更大的IP风险.

Steve Jobs' initial thoughts on VP8/WebM, a key technical antecedent to AV1.

Not surprisingly, Apple never deployed VP8 or VP9, which became problematic when YouTube 开始仅在VP9中部署4K视频. Since then, Apple has supported only standards-based codecs, most recently 2017年6月，HEVC加入HLS. On the other hand, Apple did collaborate with Microsoft on the Common Media Application Format (CMAF). As we reported back then,

While this collaboration falls far short of Apple joining the Alliance for Open Media, 这确实表明两家公司可以有效地合作. It also indicates that Apple, 长期以来，在MPEG DASH问题上一直公开不妥协, is willing to contribute to new standards that benefit the common good. Will Apple join the Alliance? “我们已经和很多公司谈过了, 招聘绝对不是我们的挑战,(AOM执行董事、微软员工)加布·弗罗斯特说. “最难的部分是工程上的努力, taking the next step, 并通过开源项目推动贡献."

So, while Apple's joining AOM is a dramatic turnaround, it's not completely unexpected.

Why Did Apple Join AOM?

许多文章将苹果的举动归因于 Mozilla声称AV1的效率将比HEVC高25-35%. 这当然是值得追逐的, 这些数字是推测性的, 我认为苹果的原因更多是战略上的，而不是财务上的.

Mozilla predicted at Demuxed that AV1 will be 25% more efficient than HEVC.

One useful analysis on this front is Jeremy Horwitz's VentureBeat article called "苹果加入开放媒体联盟的3个原因." The first reason Horwitz cited was Apple wants to add AV1 to its own devices. While true, understand that most of the mobile devices that Apple addressed by adding HEVC to HLS have HEVC decoding hardware built in, 最小化新编解码器对电池寿命的影响. We don't yet have a clear picture of how CPU-intensive AV1 decoding will be, 但如果它比HEVC复杂得多, publishers would likely prefer HEVC to preserve their viewer's battery life. The best guess is that it will take about 2 years for hardware decode to reach any consumer product.

The second reason proffered by Horwitz is more compelling: "Apple needs AV1 to stream videos to non-Apple devices.“具体来说，似乎 Apple is serious about building a content business akin to Netflix and Amazon. While as a hardware developer, 苹果可以幸灾乐祸地忽视Android设备的重要性, it can't as a content service. Netflix, in particular, has 采用VP9作为传输编解码器, initially for mobile downloads to Android devices, and then in a more expanded role. Of course, Android从版本5开始在软件中支持HEVC许多Android设备已经拥有HEVC硬件. Still, VP9是比HEVC更通用的格式, 还是不能在Chrome上播放, Firefox, Internet Explorer, or Opera. In the short term, it will be very interesting to see if and when Apple includes VP9 playback in Safari and in iOS updates. The bottom line is that if Apple is serious about becoming a player in content distribution, they had to have AV1.

霍维茨提到的第三个原因是苹果希望帮助引导AV2. While undoubtedly true, that seems so far off that I won't explore this any further.

我们对苹果的期望是什么?

苹果就是苹果，他们不说话. Our best guess is what other companies did when they joined the group, 或者我们期望他们做什么.

关于VP9, AOM成立后不久，创始成员 Microsoft added VP9 to Edge. In for a penny, in for a pound; it makes sense that Apple would do the same for Safari, MacOS, iOS, and tvOS as soon as possible. This would deliver the immediate benefit of allowing Safari viewers to play UHD videos from YouTube.

Regarding AV1, we expect Google (Chrome), Mozilla (Firefox), and Microsoft (Edge) to add AV1 decode to their browsers soon after the ink is dry on the specification. 我们最乐观的猜测是苹果也会这么做.

On the hardware front, we expect Intel, NVIDIA, ARM, 和其他成员将AV1编码/解码添加到各自的cpu, systems on a chip (SO), graphics cards, 和其他硬件设备尽快. Again, our best guess is that Apple will add AV1 hardware encode/decode to their devices as soon as possible, though, as stated, this means two years or so.

We expect YouTube to start encoding videos into AV1 format within weeks after the spec is released, 几个月后，Netflix紧随其后. Of course, both of these services currently support VP9, which is much more efficient than H.264具有类似的解码要求，并且几乎可以在任何地方播放. Apple would get the most immediate bang for their buck with VP9 support, 但我们预计到2018年年中会出现一些AV1编码的内容.

将AV1或VP9添加到HLS怎么样? Again, 根据解码要求, AV1在没有硬件支持的设备上可能不太有用, 限制短期利益. 如果苹果在其iOS设备上添加VP9支持, VP9在HLS技术上是可行的, 苹果可能也会采取这一措施.

这对一般编解码器的使用意味着什么?

When Apple added HEVC to HLS, the reaction in the HEVC encoding community was akin to finding out the Pope embraced Buddhism. You have to add HEVC today, if not sooner, to avoid falling behind the avalanche of competitors who are rushing to do so. HEVC or bust, baby! As we've seen, the reaction by actual publishers has been a bit slower.

In truth, 因为上面多次讨论的解码问题, AV1 likely won't play a significant short-term role for playback to Apple devices, though VP9 might. Still, 许多人预测AV1将面临IP挑战, as if members like Cisco, Google, Microsoft, and Intel were technically unsophisticated and would buy an IP-related pig in a poke. Apple's joining the group throws another nail in the coffin of that theory and adds to the war chest that could be used to defend those claims.

苹果的决定对消费者有什么影响呢? 它可能会极大地改变我们观看视频所用的编解码器, 虽然短期内不会, 即使是这样，我们也可能无法判断.

If you're a content producer or distributor, you now have another very strong reason to consider AV1. 如果你不从事内容销售业务, the impact will take much longer; it may be several years before you should start thinking about encoding into AV1.

Perhaps most of all, Apple's joining AOM sends a clear message to HEVC IP owners that unlike what they believed after Apple added HEVC to HLS, HEVC并不是镇上唯一的游戏. What this incredibly tone-deaf group does with this message remains to be seen.