2016年5月24日
By Jan Ozer 特约编辑
专题文章

Netflix讨论vp9相关的开发工作

这是编解码器领域的一个有趣时期, an inflection point where the power of an expensive standard is being challenged by a free, 开源编解码器. And that 开源编解码器 will soon be supplanted by another free codec from an alliance of high-tech royalty with dominating positions in the codec, content, mobile, OTT, 和CPU/GPU/SOC阵营.

昂贵的标准是HEVC (H).265)，这是众所周知的每年的版税 could exceed $60 million, with many IP owners not yet part of a pool.

The free codec is Google's VP9, which, as of April 2015, had already streamed over 250亿小时的YouTube内容. While VP9 originally seemed destined for the same obscurity suffered by its older sibling, VP8, 最近得到了Netflix等巨头的支持, JW Player, Brightcove, Telestream, and Amazon show an upturn in overall market acceptance and deployment.

基于联盟的编解码器是AV1，第一个编解码器创建 by the Alliance for Open Media, with a scheduled ship date of Q1 2017. The Alliance is promising an improvement of 50 percent over VP9 and HEVC with “reasonable increases” in encoding and playback complexity. 因为AV1很大程度上建立在谷歌的VP10之上, 这是在联盟成立之前很久的事了吗, there’s a good chance that AV1 could ship on time and on target.

The Alliance’s membership assures that AV1 will enjoy prompt deployment once available. 成员谷歌, Microsoft, 和Mozilla确保快速集成到Chrome, Edge, 和火狐, 而会员亚马逊, Google, and Netflix should start distributing AV1-encoded content soon after playback is widely available. AMD公司成员, ARM, Intel, 和NVIDIA应该在他们的cpu中提供支持, GPUs, SoCs, 和其他硬件组件, which Google and Microsoft should rapidly deploy on their mobile platforms, and Amazon and Google quickly integrate in their OTT devices.

结果不会是二元的. HEVC将主导传统广播市场, 至少在短期内是这样, 而VP9和AV1将赢得浏览器大战. But the broadcast market largely exists to feed living room TVs, which are now smarter and increasingly less connected to traditional broadcast channels. 2015年4月，Netflix的里德·黑斯廷斯宣称“线性电视已经有了惊人的50年历史. 网络电视开始发展. Clearly over the next 20 years internet TV is going to replace linear TV.“你不能说黑斯廷斯在这个问题上是中立的, but you also can’t find many people who disagree with him.

What happens to broadcast standards when the broadcast model wanes, and the streaming that used to be the tail of the distribution ecosystem becomes the dog? 我们马上就知道了.

为了找到答案，我们采访了 大卫Ronca, Netflix’s director of encoding technologies, who describes Netflix’s efforts with VP9. Netflix is a charter member of the Alliance and VP9 is the technological precursor to AV1. Netflix’s experience is a good reality check as to where VP9 stands from a performance, usability, 以及可部署性角度.

流媒体: 你什么时候开始使用VP9的?

Ronca: 我们的VP9目前正在开发中. 我们还没有播放VP9.

流媒体: 你为什么开始关注VP9?

Ronca: At the low end, VP9 provides efficiency advantages over AVC for VP9-capable mobile devices. At the high-end (4K, 10-bit) VP9 offers an alternative to HEVC.

流媒体: 你们是如何包装VP9的?

Ronca: We are using fragmented 14496-12 streams that follow the VP9 MPEG规范草案由基尔罗伊·休斯和大卫·朗卡撰写.

流媒体: DRM的任何问题?

Ronca: For fragmented MP4, Common Encryption (ISO 23001-7) works well.

流媒体: 你在哪里发布vp9编码的文件? Assume compatible browsers, what about Android or compatible OTT?

Ronca: VP9的主要目标将是移动/蜂窝和4K.

流媒体: 与H相比，数据速率节省了多少.264和HEVC?

Ronca: We are hesitant to make broad statements with respect to codec efficiency without providing the supporting data. 也就是说，我们看到VP9 vs的效果非常好. x264.Our current data suggests that VP9 is less efficient than HEVC, but still very good. We are currently conducting codec comparisons, and will publish our results around the end of summer.

流媒体: 编码时间与H相比如何.264和HEVC?

Ronca: VP9比x264慢得多. However, 我们使用高度并行化的编码模型, and we run most encodes on idle web servers which provides nearly free compute time, 因此，我们不认为编码器的速度是一个问题. That said, we believe that the current libvpx VP9 encoder would benefit from some optimizations. [Editor’s note: libvpx is the encoder executable supplied by Google.]

流媒体: 您使用的是什么编码技术? 例如, JW玩家将使用上限的CRF, and obviously single and two-pass CBR and VBR are available.

Ronca: We are exploring all of the opportunities that libvpx provides and have not yet settled on a recipe.