?? yuv.htm
字號:
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb2312">
<title>yuv4</title>
<meta name="generator" content="microsoft frontpage 3.0">
</head>
<body background="../jpg/di1.JPG">
<p align="center"><font size="6" color="#0000ff">yuv4:1:1 </font></p>
<div align="center"><center>
<table border="0" width="88%">
<tr>
<td width="100%">this reffers to common terms for y'cbcr format<br>
which separates the 'luminance' information in an<br>
image from the chroma information, allowing the resolution of<br>
chroma information to be reduced, exploiting the lack of color<br>
acuity inherent in the human visual system.<br>
<br>
there are a couple of issues with the terms in this description<br>
as explained to me by charles poynton. firstly the common use of<br>
the term luminance for y' is a misrepresentation and a distinction<br>
should be drawn between this term and true cie luminance, for<br>
example by using the term "luma", secondly the u v terms for<br>
historical reasons are associated with adjusted levels as<br>
broadcast from television transmitters and digital systems<br>
actually use y'cbcr.<br>
<br>
so yuv should more accurately mean y'cbcr.<br>
<br>
the 4:1:1 denotes the degree of compression of chroma information<br>
and makes less sense with newer formats, suffice to say that 4:1:1<br>
stores full resolution y'(luma) but 1/4 resolution of cb and cr<br>
information sampled along the horizontal axis or line.<br>
<br>
y'cbcr 4:2:2 is actually a more commonly used professional<br>
format where chroma components are only halved along the<br>
horizontal axis or line.<br>
<br>
y'cbcr 4:2:0 is used for 1/4 resolution chroma but with half<br>
resolution horizontally and half resolution vertically.<br>
<br>
4:4:4 denotes equal resolution of luminance and chroma.<br>
<br>
to generate the standard cie luminance term, from an rgb triplet<br>
y = .2125r + .7154g + .0721b, this is *different* from the y'<br>
described above.<br>
<br>
luma as stored in these video formats is actually<br>
y' = .299r'+.587g'+.114b' where the r' g' and b' terms<br>
represent scalar values which are non linear and represent<br>
gamma corrected perceptually uniform values when represented<br>
by an integer (gamma == .45).<br>
<br>
chroma terms can then be produced from these valuse:<br>
cb = b'-y'<br>
cr = r'-y'<br>
<br>
to reconstruct an rgb image from a 'yuv4:1:1' you must<br>
first resample the single cbcr sample to 4 cbcr samples<br>
to match the luminance, once this is done you should<br>
regenerate rgb triplets by reversing the above arithmetic:<br>
<br>
b' = cb +y'<br>
r' = cr +y'<br>
g' = (y'-.299r'-.114b')/.587<br>
<br>
r' b' g' represent an rgb triplet with a built in gamma<br>
correction of .45, this should look perfect when displayed<br>
on a machine with no gamma correction and a crt display<br>
(which typically have gamma transfer functions of around<br>
2.5-3.0)<br>
<br>
note that because chroma information may be negative, the<br>
cb cr values stored in any file format mey have to be adjusted<br>
accordingly. for example you would subtract 127 from an 8 bit<br>
chroma value stored in a file.<br>
<br>
don't use the luminance equation above, it is included to show<br>
the difference between luminance and luma or y' which is<br>
actually stored in the file.<br>
<br>
for more in depth information read charles a. poyntons<br>
excellent book "a technical introduction to digital video"<br>
pub, john wiley & sons, inc. isbn 0-471-12253-x<br>
<br>
cheers,angus.</td>
</tr>
</table>
</center></div>
<p align="center"><a href="../index.htm">返回</a></p>
</body>
</html>
<center>
<script type="text/javascript">
var arrBaiduCproConfig=new Array();
arrBaiduCproConfig['uid'] = 43125;
arrBaiduCproConfig['n'] = 'williamlongcpr';
arrBaiduCproConfig['tm'] = 20;
arrBaiduCproConfig['cm'] = 76;
arrBaiduCproConfig['um'] = 26;
arrBaiduCproConfig['rad'] = 1;
arrBaiduCproConfig['w'] = 728;
arrBaiduCproConfig['h'] = 90;
arrBaiduCproConfig['bd'] = '#24581B';
arrBaiduCproConfig['bg'] = '#E1FDE8';
arrBaiduCproConfig['tt'] = '#0000CC';
arrBaiduCproConfig['ct'] = '#006600';
arrBaiduCproConfig['url'] = '#666666';
arrBaiduCproConfig['bdl'] = '#ffffff';
arrBaiduCproConfig['wn'] = 4;
arrBaiduCproConfig['hn'] = 1;
arrBaiduCproConfig['ta'] = 'right';
arrBaiduCproConfig['tl'] = 'bottom';
arrBaiduCproConfig['bu'] = 0;
</script>
<script type="text/javascript"
src="http://cpro.baidu.com/cpro/ui/ui.js">
</script>
<script type="text/javascript">
<!--
document.write(baiduCproIFrame());
-->
</script>
</center>
<br><br><br>
<div align="center"><center>
<table cellspacing="0" cellpadding="1" border="0" width="770" style="font-size: 9pt;" >
<tr><td width="770" bgcolor="#000000" height="1"></td></tr>
<tr><td width="770" height="5"></td></tr>
<tr>
<td align="center" width="770">
<a href="/" target="_top">月光軟件</a>┊<a href="/download/" target="_top">程序下載</a>┊<a href="/doc/" target="_top">編程文檔</a>┊<a href="/book/" target="_top">電腦教程</a>┊<a href="/web/" target="_top">網站設計</a>┊<a href="/site/" target="_top">網址導航</a>┊<a href="/art/" target="_top">網絡文學</a>┊<a href="/game/" target="_top">游戲天地</a>┊<a href="/joke/" target="_top">幽默笑話</a>┊<a href="/life/" target="_top">生活休閑</a>┊<a href="/picture/" target="_top">美女圖片</a>┊<a href="/guestbook/" target="_top">意見反饋</a><br>
<a href="/program/doc/docelite1105.htm">電腦技術</a>┊<a href="/program/doc/docelite405353.htm">編程開發</a>┊<a href="/program/doc/docelite25188.htm">網絡專區</a>┊<a href="/program/doc/docelite10811.htm">談天說地</a>┊<a href="/program/doc/docelite113108.htm">情感世界</a>┊<a href="/program/doc/docelite872697.htm">游戲元素</a>┊<a href="/program/doc/docelite50820.htm">分類游戲</a>┊<a href="/program/doc/docelite166458.htm">熱門游戲</a>┊<a href="/program/doc/docelite42994.htm">體育運動</a>┊<a href="/program/doc/docelite872698.htm">手機專區</a>┊<a href="/program/doc/docelite28075.htm">業余愛好</a>┊<a href="/program/doc/docelite34403.htm">影視沙龍</a>
<br>
<a href="/program/doc/docelite872701.htm">音樂天地</a>┊<a href="/program/doc/docelite872702.htm">數碼廣場</a>┊<a href="/program/doc/docelite121902.htm">教育園地</a>┊<a href="/program/doc/docelite872703.htm">科學大觀</a>┊<a href="/program/doc/docelite991826.htm">古今縱橫</a>┊<a href="/program/doc/docelite49868.htm">談股論金</a>┊<a href="/program/doc/docelite55064.htm">人文藝術</a>┊<a href="/program/doc/docelite165391.htm">醫學保健</a>┊<a href="/program/doc/docelite115338.htm">動漫圖酷</a>┊<a href="/program/doc/docelite872704.htm">二手專區</a>┊<a href="/program/doc/docelite112364.htm">地方風情</a>┊<a href="/program/doc/docelite165368.htm">各行各業</a>
<br><br>
<a href="http://www.moon-soft.com/">月光軟件站</a>·<a href="/sitemap.htm" target="_blank">版權所有</a>
</td></tr>
</table>
</center></div>
<!-- */ //-->
?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -