3:2 Pulldown and Deinterlacing_1

本文由MagicAlex翻译自网站：

http://www.theprojectorpros.com/learn.php?s=learn&p=theater_pulldown_deinterlacing

此博文供大家学习交流。本人翻译水平有限，有什么专业性术语、概念出错也是应该的哈。英文原文与译文对照编排，方便理解离谱的译文。

本文适合了解一定场，帧，扫描类型，制式概念的同学阅读。遇到不理解的概念又找不到相关信息的苦逼同学，请在博文后评论处留言。

正文：

Deinterlacing is defined as the changing of an interlaced image into a progressive scan image.

反交错的定义：将交错的图像转换成逐行扫描的图像。（p.s.这里的图像更指视频吧。。。）

Most of the newer technology display devices have some type of deinterlacer built into them, but just as in

绝大多数的新型显示器本身拥有去交错的硬件设备来反交错，相对的，（p.s.新显示器是区别于CRT这类的老一辈）

scaling, how well it is performed is critical to the image quality you see.

反交错的质量就决定了你所看到的图像的质量。

Video comes to your display in two forms: video from a video camera and video produced from film. Both

平时大家接触的视频有两种来源：一是来自录像机，二是来自电影的胶卷过带。两者

present their own unique challenges for a deinterlacer.

都有自己独特的反交错要求。

Video originally from a video source, as in anything that would be shot by a video camera instead of film, is

视频的讯源若是Video型，也就是图像是由录像机拍摄，是区别于电影的拍
摄得到的，那么

recorded in individual fields. (Remember, a field equals one half of a frame).

该视频信息是记录在一个个场中的。（记住，一个场等于一帧的一半）。

In NTSC, these fields consist of 240 lines of information, or half the resolution needed for a full frame. The

在NTSC视频制式中，这些场是由240行信息组成，或者是一帧分辨率的一半。

problem is that these two fields — one with the odd lines of information of the frame and one with the even

问题就在于每两种场 — 一是存储了一帧中的奇数行信息，另一个则是存储了偶数

lines of information for the frame — are not actually recorded at the same time.

行信息 — 存储的信息是不能正好来自于同一时间的。

If everything is motionless, there isn’t a problem with simply taking the odd field and adding it to the even

如果视频的场景是静止的，那也就不存在问题：只要将奇数场与偶数场两两合并，

field, to make up one full progressive frame of information. Everything would look great. The problem

这样的结果不言而喻：合成了一个完整的帧的信息。处理后的视频是完美的逆天了！恼人的事实却是

therein lies with motion. If there is motion between the time the odd field is captured and when the even

正常的视频肯定有动景。如果一个动作的拍摄是介于奇数场俘获

field is captured by the camera, you can’t simply add the two fields together to create a frame. When these

与偶数场俘获之间的，那么你无法简单的合并两个场来生成一个帧从而反交错。当这些

fields are played back in interlaced form, one after the other, the difference in fields isn’t noticeable because

场以交错的形式播放时，一个挨着一个（p.s.交替），它们之间的不同之处是不会被察觉的，这是由于

they are not shown at the same time. However, if you were to simply add the fields together to form a

它们的拍摄并非是同时的。然而，如果你简单的用相加两个场的方法来形成一个

progressive scan image, you would get something that looks like this:

逐行扫描的视频，你将看到“一丝丝”，比如像这样车：

Because this car is moving, just adding the two fields together won’t work. The resulting jagged edges seen

正是由于车是飞快的移动的，仅仅只是相加两个场是无法反交错的。合成的结果产生了锯齿边缘，这就是

above are a sure sign of poor deinterlacing and are called “jaggies”.

失败的反交错的典型特征之一哟，我们称之为“锯齿线”

A good deinterlacer will solve this by comparing the separate fields, field one versus. field two. In areas of

高质量的反交错会通过比较各个单独的场，场一与场二比较，来解决锯齿问题。在高速

high motion, it interpolates (averages) the two areas to create that portion of the progressive frame, while at

运动场景中，反交错程序会插入两个场的两个运动区域图像的平均值而生成渐进式的帧，同一

the same time it combines only the areas that are not in motion. This process is called motion adaptive

时间，程序又直接合并了两场那些静止的区域。这种反交错的方法称为“动态适应性

deinterlacing. The resulting image is smoothed out as follows:

去交错”。处理后的图像：