2017年3月29日
By 1月时特约编辑
专题文章

2017年编解码器现状

随着HEVC的推进和配方的推出开放媒体联盟, 2015 was the most disruptive year in recent history as it related to the adoption and deployment of video codecs. 而2016年则没有这么剧烈, there were a number of significant events that will impact how we choose and use video codecs over the next few years, 给大家一个特别不愉快的节日礼物.264个用户. 我在这里主要按时间顺序来讨论.

2016年1月:.S. HDR市场在双技术途径下趋同

1月. 5, Dolby announced that LG’s 2016 OLED TVs and Super UHD TVs would feature Dolby Vision HDR technology, signaling that Dolby Vision will likely become the de facto premium HDR technology in the U.S.HDR10作为免版税但功能较差的替代方案. 不可否认, this date is arbitrary; we could have selected March, when Dolby announced that Amazon would support Dolby Vision in its streaming 4K titles, 或6月, 沃尔玛的Vudu也做了同样的事情. 关键是对杜比视界HDR的支持正在整合. 几乎所有支持杜比视界的电视都将支持HDR10, 是什么让电视机制造商可以安全生产, 消费者购买, HDR 4K电视.

这很重要, because the advantages of 4K-only solutions over 1080p TVs are minimal under most normal viewing conditions. In contrast, HDR significantly improves the viewing experience under virtually all conditions. 不幸的是, actual HDR deployment by content developers has been slowed by the lack of a de facto standard.

杜比视界比HDR10有很多优势, 包括与10位相比的12位支持, and dynamic metadata that can be adjusted on a scene-by-scene or even frame-by-frame basis. In contrast, HDR10 uses static metadata sent at the beginning of the movie. 杜比视界也可以支持多达10个,000尼特的亮度与4,HDR10是1000尼特, 虽然目前还不清楚硬件何时可以显示10,000尼特将可用.

幸运的是, content producers can master for Dolby Vision with fallback support for both HDR10 and even standard dynamic range displays, 简化生产和分销. 整体, 2017 should become the year it’s actually safe to invest in a high-end 4K HDR-capable TV set, 至少在美国是这样.S. 在欧洲, BBC正在推广HLG (Hybrid Log-Gamma) HDR技术, 它是与日本广播公司NHK合作开发的. So far, while there are some projectors that support HLG, few if any TVs do. 然而, 不像杜比视界, 哪些需要设备的硬件支持, HLG应该可以通过固件更新进行现场升级. So if HLG ever becomes popular in the States, many HDR TVs should be able to support it.

杜比视界HDR似乎成为了事实上的高端HDR标准.

2016年3月:Beamr收购Vanguard

今年3月, Beamr, an Israeli-based video optimization vendor, bought codec vendor Vanguard Video. 这一点很重要，原因有几个. 从技术角度来看, 结合 will enable Beamr’s optimization technology to be used within Vanguard’s already highly regarded H.264和H.265编解码器，而不是作为后处理应用. 从质量和工作流程的角度来看，这更有效, 尽管Beamr尚未宣布该解决方案的可用性.

从纯重量的角度来看, 结合, 这是由一轮1500万美元的私人融资促成的, gives the combined company the ability to compete with larger encoding companies like Elemental Technologies and Harmonic. The merger is already bearing fruit; in December, Verizon公司, Verizon Communications的风险投资部门, 威瑞森数字媒体服务公司和其他相关公司的所有者, 向Beamr投资了400万美元. This investment likely foreshadowed the use of Beamr’s codec-related technology by Verizon Digital Media Services, 以及其他家族成员.

2016年6月:苹果在HLS中支持碎片化MP4

在2016全球开发者大会上, Apple announced that HTTP 在线直播 (HLS) will support the Common Media Application Format (CMAF), a file packaging specification jointly authored by Apple and Microsoft. 为什么这很重要?? 以前, HLS only supported files packaged in the MPEG-2 Transport Stream container, 而基于HTTP的动态自适应流(DASH)标准, and proprietary technologies like Microsoft’s Smooth Streaming and Adobe’s HTTP Dynamic Streaming (HDS), 支持打包在碎片化MP4容器中的文件(fMP4). This meant that many publishers needing DASH and HLS support for their various playback targets had to produce and store files in both formats. CMAF支持与HLS和DASH兼容的单一格式.

The fly in the ointment is that CMAF enables two incompatible common encryption modes: cipher block chaining (CBC) for Apple’s FairPlay digital rights management (DRM) technology, 和计数器模式(CTR)的PlayReady, 都, 和其他数字版权文件. Content encrypted with CBC can’t be decrypted by PlayReady-compatible clients, while content encrypted with CTR can’t be decrypted by FairPlay clients.

Google通过在都中支持CBC来最小化这个问题, 包括Android平台吗, 以及Chrome和Firefox. 直到微软为PlayReady和Edge做同样的事情, 然而, 我们被困在两个零散的MP4数据孤岛上, 一个用CBC加密, 另一个CTR. Or, 更有可能, 直到《百家乐app下载》在所有平台上播放, most producers will likely stick with HLS content encapsulated in an MPEG-2 transport stream wrapper, 和DASH在fMP4.

2016年8月:苹果悄然弃用TN2224

苹果科技笔记TN2224 has been the Rosetta Stone for encoding professionals since its initial publication in March 2010, providing general guidance regarding how to formulate an encoding ladder, as well as specific guidance on encoding for HTTP 在线直播 (HLS). 8月. 2, 苹果公司毫不客气地弃用了TN2224，并给出了一个简短的说明, “Important: This document is concerned with practices and with the rationale behind them. For detailed requirements please refer to the HLS Authoring Specification for Apple Devices.“好吧，至少苹果说这很重要.

有趣的是，直到12月. 12, the HLS Authoring Specification for Apple Devices had been named the Apple Specification for Apple TV. 在那一天，苹果修改了标题，适用于所有苹果设备. The net effect is that where you used to look to TN2224 for specific guidance for encoding for HLS, 现在你应该看看苹果设备规范.

如果你有段时间没看TN2224的话, 最近的变化, 以及那些由苹果设备规范产生的, 都是戏剧性的. Apple now recommends a keyframe interval of 2 seconds (as compared with 3 seconds) and a segment length of 6 seconds (as compared with 9 seconds). 编码阶梯本身已经被彻底改造了, 苹果公司现在批准使用高达200%的受限VBR, 也许是最重要的变化.

除了, 苹果规范建议使用High profile, 而不是基线或主要, 淘汰了几款老款iPhone, and dictates that all 30i content should be deinterlaced to 60p rather than 30p, 奇怪的是，比起细节，他更喜欢平滑. 最后, the Apple Devices spec states that the 2000 kbp variant in the encoding ladder should be the first variant listed in the master playlist file, 让它成为玩家第一个检索到的内容. 底线是，如果你在编码HLS, 你应该看看苹果设备的规格说明, 特别是如果流媒体应用程序需要app Store的批准.

August 2016: Netflix Loudly Proclaims HEVC Superior to VP9, Then Quietly Recants

8月. 31, Netflix’s Jan De Cock presented the results of a massive Netflix internal study to the SPIE Applications of Digital Image Processing conference in a presentation titled, 大规模视频编解码器x264的比较, x265和libvpx的实际视频点播应用.” One of the most significant findings was that when measured with Netflix’s VMAF benchmark, x265 proved about 20 percent more efficient than VP9 (libvpx) at all tested resolutions.

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