隔行扫描，视频分辨率

H.264即MPEG-4.10，SMPTE 421M（VC-1）是其有力的竞争者。

隔行扫描（interlaced），分成两场传输一帧，每次传输的数据量是少了一半，但是一帧画面传输的时间被拉长了，不知道这样理解对不对？原文如下：

In the early days of television, a technique called “interlacing” was used to reduce the amount of information sent for each image. By transferring the odd-numbered lines, followed by the even-numbered lines, the amount of information sent for each image was halved. Interlacing is still used for most consumer applications, except for computer monitors and some new digital television formats. 

可是这一段如何理解呢：

With interlace, each scan line is refreshed half as often as it would be if it were a progressive display. Therefore, to avoid line flicker on sharp edges due to a too-low refresh rate, the line-to-line changes are limited, essentially by vertically lowpass filtering the image. A progressive display has no limit on the line-to-line changes, so is capable of providing a higherresolution image (vertically) without  licker.

视频分辨率（Video Resolution），通常用lines of resolution来度量视频质量，没搞懂这段话：

In essence, how many distinct black and white vertical lines can be seen across the display? This number is then normalized to a 1:1 display aspect ratio (dividing the number by 3/4 for a 4:3 display, or by 9/16 for a 16:9 display). Of course, this results in a lower value for widescreen (16:9) displays, which goes against intuition.

标清：480i/576i，对于固定像素（非CRT）具有4：3宽高比的显示器通过转换后，对应720*480i/720*576i的有效分辨率；16：9的宽高比，对应960*480i/960*576i。

增强清晰度：480p/576p，对于固定像素（非CRT）具有4：3宽高比的显示器通过转换后，对应720*480p/720*576p的有效分辨率；16：9的宽高比，对应960*480p/960*576p。

高清：720p/1080i，对于固定像素（非CRT）具有16：9的宽高比，对应1028*720p/1028*1080i。

这段话看不懂：

但是，HDTV显示器在技术上定义为能够显示最少720p或1080i有效扫描线。它还必须能够用至少540逐行（540p）或810隔行（810i）有效扫描线来显示16：9的视频画面。这样，在制造具有4：3宽高比、基于CRT的HDTV和具有16：9宽高比、分辨率为1024*1024p、1280*768p、1024*768p的LCD/等离子等显示器时，能够降低制造费用。