What Is 2K and 4K Video?
This is another installment in our series of "What Is...?" articles, designed to offer definitions, history, 以及围绕在线视频行业的重要术语和问题的背景.
Soon, 普通消费者将有机会使用平板“超高清”显示器，使客厅里的1080p“真高清”高清电视的分辨率看起来几乎和老式模拟电视的质量差不多. 这些新显示器只使用2K和4K分辨率中的一种，消费者和内容制作商将在未来几年内面对这些分辨率.
2K和4K分辨率到底是什么，它们与今天的高清电视分辨率有什么不同? 更重要的是，流媒体行业应该采取什么方法来应对这些新决议?
720p and 1080p HDTV
当平板高清电视首次达到关键的消费群体时, the format was 720p, or 720 vertical lines of resolution, 在美国以每秒24帧或30帧的递进(P)速率播放. While the US based its HD television resolutions on NTSC, 欧洲使用PAL，这意味着720p的P是恒定的25 fps.
在模数转换期间，720p显示器充斥了市场, 消费电子产品制造商认为是时候将消费者推向“真高清”或1080p了, with its 1080 lines of vertical resolution. 忽略了绝大多数高清广播都是480i或720p的事实, “真高清”的推动成为通过蓝光播放器提供优质内容的一种方式, to a lesser extent, digital downloads and streaming.
Using 720p and 1080p as baselines, 分别具有1280 x 720和1920 x 1080像素分辨率, 让我们看看新的2K和4K格式如何与高清和真高清显示器相比较. Keep in mind that, as of early March 2013, 我们还没有4K播放的优质内容, although as mentioned in an article on the 2013 Mobile World Congress, that is beginning to change.
2K Video
We'll start with the simplest format, 作为一种描述消费电子(CE)公司如何将分辨率的定义从垂直线转向更模糊的东西的方式.
If 1080p has 1080 lines of vertical resolution, one would think that the 2K displays have 2,000 lines of vertical resolution, right? Not so fast: 2K is an incremental bump above 1080p. In fact, 2K doesn't even change the vertical resolution, leaving it at 1080 lines, 并且只将水平分辨率提高到2048像素宽度.
计算一下，你会发现从1920个水平像素到2048个水平像素的增加是惊人的3.43 per cent increase. 几乎不值得把1080p的“真高清”显示器换成2K的.
造成这种混淆的原因主要在于2K分辨率的主要目的. To date, 2K主要用于电影院里的投影, 它们需要的宽高比与消费高清电视和电脑显示器略有不同.
While consumer displays use a 16:9 aspect ratio (or 1.777:1(如果换算成最小公分母)，则 Digital Cinema Initiative (DCI)由好莱坞主要工作室支持，使用17:9的宽高比(约为1:9).85:1)，它更适合用于拍摄和放映电影的35mm和70mm胶片格式.
As such, the DCI termed the 2048 x 1080 resolution as 2K, 即使是在消费者应用领域，这个名字也经久不衰. 难怪大多数拥有体面家庭影院系统的消费者觉得他们获得了与电影院同等或更好的体验:除了水平像素多一些, the image is exactly the same resolution in 1080p and 2K, 像素密度(以PPI或每英寸像素计算)在消费级1080p显示器上相当密集.
另一种看待它的方式是整体像素:1920 x 1080等于2,073,600 pixels, while 2K at 2048 x 1080 equals 2,211,840. The difference is 138,240 pixels, and if the pixels were represented as megapixels (Mpx, (我们衡量静止相机分辨率的典型方法)1080p和2K之间的变化大约为0.13 Mpx (2.1 versus 2.2 Mpx).
4K Video
Now that we've looked at 2K, what about 4K? Does it offer resolution benefits beyond 2K and 1080p?
有三种4K分辨率需要考虑，每种分辨率都有不同的宽高比.
Let's consider, first, the DCI version of 4K. 电影行业喜欢拍摄分辨率至少是实际放映分辨率的3-4倍, 所以DCI在推出4K规格的同时也推出了2K显示规格.
DCI 4K具有2160条垂直线的分辨率，是1080p的两倍. So far so good, but what about the horizontal resolution? It clocks in at 4096 pixels. All told, that's 8,847,360 pixels, or 8.84 Mpx.
Running the numbers, that means DCI 4K is 4.是1080p分辨率的26倍，2K分辨率的4倍. 正如我们上面提到的，区别在于1080p(16:9)和DCI 2K / 4K(17:9)的宽高比。.
4K Ultra HD (UHD) Video
Ok, 现在我们已经看到DCI 4K的像素是1080p的四倍, 你这个月可以从三星买到的4K超高清显示器呢, Sony, and others for a cool $25,000 at sizes ranging from 55 to 84 inches?
4K UHD does double the vertical resolution, from 1080 to 2160 vertical lines of resolution, but it falls short of the 4,000 pixel horizontal resolution, clocking in at 3840 horizontal pixels. 如果你注意到水平分辨率翻倍的模式, 你已经明白4K UHD不是真正的4K的原因了:1920乘以2等于3840, 这意味着消费者显示器仍将保持16:9的宽高比.
Related Articles
Over 100,000 creators use Patreon to run their creative businesses, 品牌可以利用这个平台的热情和百家乐软件. Here's how to succeed on Patreon.
06 Nov 2019
将超高清视频传输到家中需要进行严格的压缩. 寻找HEVC编解码器，使视频分辨率的下一个飞跃成为可能.
30 Dec 2013
2K和4K电视能产生3d电视所缺乏的兴奋感吗? Manufacturers hope so. Here's what it will take.
12 Apr 2013