！！超级冷水帖！XO根本就是输出模拟信号！

差距的话，只是讨论色差和HDMI，模拟和数字没有什么实用价值

这个问题可以从两个方面考虑

1。电视。在你自己家的电视上，仔细比较一下色差和HDMI的画质差距。没有HDMI电视的同学不要着急，想买的时候再去商场或者别的用户家比较。不考虑买HDMI电视的同学，就不要太上心了，PS3，XO都有色差

2。游戏机。PS3和XO的画质，论坛里面有很多帖子，谁好谁坏见仁见智，PS3首发以后这个问题会更加明朗一些。

离开这两个问题，其他说什么都是瞎扯。

晕倒，满口胡言乱语，只是对了版主的胃口就可以加分？R版莫非把自己当皇帝了？

给两个联动网址

英文好的同学：http://www.avsforum.com/
英文不好的同学：国内论坛都是口水，给个官网吧。http://cn.hdmi.org/

想看英文吗？

DVI vs. HDMI vs. Component Video -- Which is Better?
Posted by Admin on Monday, February 14, 2005 - 03:15 am: [ Submit News ] [ Reply ]  

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As DVI and HDMI connections become more and more widely used, we are often asked: which is better, DVI (or HDMI) or component video? The answer, as it happens, is not cut-and-dried.

First, to clear away one element that can be confusing: DVI and HDMI are exactly the same as one another, image-quality-wise. The principal differences are that HDMI carries audio as well as video, and uses a different type of connector, but both use the same encoding scheme, and that's why a DVI source can be connected to an HDMI monitor, or vice versa, with a DVI/HDMI cable, with no intervening converter box.

The upshot of this article--in case you're not inclined to read all the details--is that it's very hard to predict whether a digital DVI or HDMI connection will produce a better or worse image than an analog component video connection. There will often be significant differences between the digital and the analog signals, but those differences are not inherent in the connection type and instead depend upon the characteristics of the source device (e.g., your DVD player) and the display device (e.g., your TV set). Why that is, however, requires a bit more discussion.

What are DVI, HDMI and Component Video?

DVI/HDMI and Component Video are all video standards which support a variety of resolutions, but which deliver the signal from the source to the display in very different ways. The principal important difference is that DVI/HDMI deliver the signal in a digital format, much the same way that a file is delivered from one computer to another along a network, while Component Video is an analog format, delivering the signal not as a bitstream, but as a set of continuously varying voltages representing (albeit indirectly, as we'll get to in a moment) the red, green and blue components of the signal.

Both DVI/HDMI and Component Video deliver signals as discrete red, green, and blue color components, together with sync information which allows the display to determine when a new line, or a new frame, begins. The DVI/HDMI standard delivers these along three data channels in a format called T.M.D.S., which stands for "Transmission Minimized Differential Signaling." Big words aside, the T.M.D.S. format basically involves a blue channel to which horizontal and vertical sync are added, and separate green and red channels.

Component Video is delivered, similarly, with the color information split up three ways. However, component video uses a "color-difference" type signal, which consists of Luminance (the "Y", or "green," channel, representing the total brightness of the image), Red Minus Luminance (the "Pr," or "Red," channel), and Blue Minus Luminance (the "Pb," or "Blue," channel). The sync pulses for both horizontal and vertical are delivered on the Y channel. The display calculates the values of red, green and blue from the Y, Pb, and Pr signals.

Both signal types, then, are fundamentally quite similar; they break up the image in similar ways, and deliver the same type of information to the display, albeit in different forms. How they differ, as we'll see, will depend to a great extent upon the particular characteristics of the source and display devices, and can depend upon cabling as well.

Isn't Digital Just Better?

It is often supposed by writers on this subject that "digital is better." Digital signal transfer, it is assumed, is error-free, while analog signals are always subject to some amount of degradation and information loss. There is an element of truth to this argument, but it tends to fly in the face of real-world considerations. First, there is no reason why any perceptible degradation of an analog component video signal should occur even over rather substantial distances; the maximum runs in home theater installations do not present a challenge for analog cabling built to professional standards. Second, it is a flawed assumption to suppose that digital signal handling is always error-free. DVI and HDMI signals aren't subject to error correction; once information is lost, it's lost for good. That is not a consideration with well-made cable over short distances, but can easily become a factor at distance.

So What Does Determine Image Quality?

Video doesn't just translate directly from source material to displays, for a variety of reasons. Very few displays operate at the native resolutions of common source material, so when you're viewing material in 480p, 720p, or 1080i, there is, of necessity, some scaling going on. Meanwhile, the signals representing colors have to be accurately rendered, which is dependent on black level and "delta," the relationship between signal level and actual as-rendered color level. Original signal formats don't correspond well to display hardware; for example, DVD recordings have 480 lines, but non-square pixels. What all of this means is that there is signal processing to go on along the signal chain.

The argument often made for the DVI or HDMI signal formats is the "pure digital" argument--that by taking a digital recording, such as a DVD or a digital satellite signal, and rendering it straight into digital form as a DVI or HDMI signal, and then delivering that digital signal straight to the display, there is a sort of a perfect no-loss-and-no-alteration-of-information signal chain. If the display itself is a native digital display (e.g. an LCD or Plasma display), the argument goes, the signal never has to undergo digital-to-analog conversion and therefore is less altered along the way.

That might be true, were it not for the fact that digital signals are encoded in different ways and have to be converted, and that these signals have to be scaled and processed to be displayed. Consequently, there are always conversions going on, and these conversions aren't always easy going. "Digital to digital" conversion is no more a guarantee of signal quality than "digital to analog," and in practice may be substantially worse. Whether it's better or worse will depend upon the circuitry involved--and that is something which isn't usually practical to figure out. As a general rule, with consumer equipment, one simply doesn't know how signals are processed, and one doesn't know how that processing varies by input. Analog and digital inputs must either be scaled through separate circuits, or one must be converted to the other to use the same scaler. How is that done? In general, you won't find an answer to that anywhere in your instruction manual, and even if you did, it'd be hard to judge which is the better scaler without viewing the actual video output. It's fair to say, in general, that even in very high-end consumer gear, the quality of circuits for signal processing and scaling is quite variable.

Additionally, it's not uncommon to find that the display characteristics of different inputs have been set up differently. Black level, for example, may vary considerably from the digital to the analog inputs, and depending on how sophisticated your setup options on your display are, that may not be an easy thing to recalibrate.

The Role of Cable and Connection Quality

Cable quality, in general, should not be a significant factor in the DVI/HDMI versus Component Video comparison, as long as the cables in question are of high quality. There are, however, ways in which cable quality issues can come into play.

Analog component video is an extremely robust signal type; we have had our customers run analog component, without any need for boosters, relays or other special equipment, up to 200 feet without any signal quality issues at all. However, at long lengths, cable quality can be a consideration--in particular, impedance needs to be strictly controlled to a tight tolerance (ideally, 75 +/- 1.5 ohms) to prevent problems with signal reflection which can cause ghosting or ringing.

DVI and HDMI, unfortunately, are not so robust. The problem here is the same as the virtue of analog component: tight control over impedance. When the professional video industry went to digital signals, it settled upon a standard--SDI, serial digital video--which was designed to be run in coaxial cables, where impedance can be controlled very tightly, and consequently, uncompressed, full-blown HD signals can be run hundreds of feet with no loss of information in SDI. For reasons known only to the designers of the DVI and HDMI standards, this very sound design principle was ignored; instead of coaxial cable, the DVI and HDMI signals are run balanced, through twisted-pair cable. The best twisted pair cables control impedance to about +/- 10%. When a digital signal is run through a cable, the edges of the bits (represented by sudden transitions in voltage) round off, and the rounding increases dramatically with distance. Meanwhile, poor control over impedance results in signal reflections--portions of the signal bounce off of the display end of the line, propagate back down the cable, and return, interfering with later information in the same bitstream. At some point, the data become unrecoverable, and with no error correction available, there's no way to restore the lost information.

DVI and HDMI connections, for this reason, are subject to the "digital cliff" phenomenon. Up to some length, a DVI or HDMI cable will perform just fine; the rounding and reflections will not compromise the ability of the display device to reconstruct the original bitstream, and no information will be lost. As we make the cable longer and longer, the difficulty of reconstructing the bitstream increases. At some point, unrecoverable bit errors start to occur; these are colloquially described in the home theater community as "sparklies," because the bit errors manifest themselves as pixel dropouts which make the image sparkle. If we make the cable just a bit longer, so much information is lost that the display becomes unable to reconstitute enough information to even render an image; the bitstream has fallen off the digital cliff, so called because of the abruptness of the failure. A cable design that works perfectly at 20 feet may get "sparkly" at 25, and stop working entirely at 30.

In practice, it's very hard to say when a DVI or HDMI signal will fail. We have found well-made DVI cables to be quite reliable up to 50 feet, but HDMI cable, with its smaller profile, is a bit more of a puzzle. Because the ability to reconstitute the bitstream varies depending on the quality of the circuitry in the source and display devices, it's not uncommon for a cable to work fine at 30, 40, or 50 feet on one source/display combination, and not work at all on another.

The Upshot: It Depends

So, which is better, DVI or component? HDMI or component? The answer--unsatisfying, perhaps, but true--is that it depends. It depends upon your source and display devices, and there's no good way, in principle, to say in advance whether the digital or the analog connection will render a better picture. You may even find, say, that your DVD player looks better through its DVI or HDMI output, while your satellite or cable box looks better through its component output, on the same display. In this case, there's no real substitute for simply plugging it in and giving it a try both ways.

嘿嘿,来战么....我等了好久了..那两个网站我看都表看..因为我早就看烂了....HDMI1.3的规格我明白的很...

话说,我哪儿满口胡言乱语了?

这文章国内唯一的中文版本是我翻译的...当然..是以前翻的...所以现在拿出来看有不少地方翻译得用词不够准确...

文章是在HDMI1.3之前出来的..1.3教之前的规格有了很大提升...

当然..仅仅是规格上....我不认为人的肉眼能够分辨出来..同样也不认为现阶段有足够好的信号源来匹配HDMI1.3...

[ 本帖最后由 winterb 于 2006-11-3 23:43 编辑 ]

AVS 上面两三个月前狂喷蓝光电影不如hd dvd电影，不知道大家看到没？

模拟和数字，从极限上来说哪个好，恐怕是模拟，我们生活在模拟的世界，所有数字信号都是采样。照片图像，声音，视频都说明这个道理。

但是在实际应用中呢？

比如考虑PS3，XO这样全数字处理的低档的视频源

比如考虑几乎是数字处理的大屏幕回放设备，投影设备

甚至比如考虑我们手中民用普通的视频线

藕是小白，藕上论坛是向高手请教来的

另外，求LSSS翻译的中文版地址

[ 本帖最后由 藕是张力 于 2006-11-4 00:13 编辑 ]

数字？模拟？Do U? under stand?

http://www.htpchome.net/data/2006/0615/article_924.html

我是低调的人,我翻译的原文,虽然有用词不恰当的地方,但是对于E文原文的理解都没有出错,不会产生歧义

同LS....你刚才的发言我没有看懂.....

数字和模拟本来就不是处在一个层面上的东西..很难直接比较.不过我个人觉得数字来得先进一点.但是先进和好并不是一个概念.

对于现在色差和HDMI的讨论.有很多的误解.当然,我首先肯定数字化是趋势.并不是说比模拟效果好,而是处于容易控制的考虑,一个例子就是HDCP.如果我是厂家也大力推广数字化.因为可以有效避免D版

回到色差和HDMI的问题.很多人说HDMI效果好,有两个原因.1.使用的线才...你买了一根组的色差线.拿来和一根几百的HDMI线来比较..这是不公平的.就好象车一样,越是好的车对于道路的要求就越搞.HDMI和色差也一样
2.处理电路的问题.处理色差和HDMI是通过不同的处理电路的.由于数字化的趋势,对于数字电路的研究这几年的进展远远大于模拟电路.这也造成了显示效果数字要高于模拟.

如果单单要讨论模拟和数字谁好,对谁都是不公平的.老话,数字是趋势....模拟被取代是不可避免的.是由于市场的需要.

从winterb这里学到了不少东西，语言很有逻辑性，而且就事论事。

拜一下。

winterb兄，联动http://www.tgfcer.com/club/thread-5814843-1-1.html

欢迎赐教

我想说的是，除非脑后插管，不然肉眼看到的东西都是模拟的～！

个人觉得能，如果是玩游戏，数字信号效果更好些，因为游戏内部图像处理都是数字的，输出的时候D/A一次，总有损耗吧
而看影片就不同，不说胶片的，即使数字录像机拍摄的，其实都是镜头捕捉模拟信号以后经过A/D才记录在带子上，所以要不停的提高，10比特量化，甚至12比特

对家庭而言，还是要方便好用有便宜~~~~

色差真的可以1080P？期待达人的评测～～～