有人说HDMI线只要通效果都一样（线圣高级副总裁答疑16页229楼）（请大家文明讨论）

九十九龙马

原帖由 HiViUser 于 2008-8-22 19:27 发表
平定貴 ？

每個人心中、手中、耳中、眼中、口袋中、 .....

尺度、要求、選擇、 ....

完全不一樣。

http://ww ...

哇 贵价线要多好几颗螺钉 真的很漂亮  而且螺钉都镶金边了！！[s:47] [s:46] [s:94]

九十九龙马

原帖由 xtal 于 2008-8-22 21:34 发表

都是钻研过模拟电子的，握手！
数字传输不是模拟传输，误码不会局限于最低位，而是任何位都有可能，
因此误码更多的表现为噪点的形式，
尤其是暗场景，一旦数据误码出现在高位，会出现非常明显的亮点

那我用PC通过HDMI传输纯黑色的图片到显示器显示 有机会能看到黑底上出现的亮点吗  我刚才试过了一下看了半分钟 没有发觉任何的亮点  证明误码率不是想象中的那么高 估计这个概率很小很小很小

九十九龙马

原帖由 notrueccf 于 2008-8-22 20:36 发表
我读书时曾花了很多时间在模电上，差点进入hifi友之列。不过我更喜欢计算机，进入大学后大多时间都花在单片机上了。可以说模电数电都有较多了解。毕业之后在电力行业做了5年，所以有人拿输电的“skin effct”来忽悠， ...

内存也是有校验的 在大负荷的工作状态下需要校验内存数据提高稳定性 公司用的电脑内存都带校验的 家里用的电脑就是普通内存

notrueccf

呵呵，那是ECC内存，只有服务器和专业工作站才用（比如你们公司的图形工作站），因为ECC内存不但贵而且速度慢，一般是不用的。现在的技术普通PC就可以把FSB做到800M，普通PC是没有校验的，事实上完全没有问题，只要主板、内存没有故障，数据是极少出错的，数字通信的优点就在于抗干扰能力非常强。

“比较的线材一根是1千多显示器自带的线 一根是4万显示器自带的线
当然或许因为显示器厂家认为线材不重要所以4万显示器自带的线也是很普通的线也不定 ”---我相信，你和我的观点一致：即使高端的专业图形工作站，也不会有厂家为了提升效果而给它配几千元一条的电源线或数据线。

搜索了一下，AudioQuest公司产品开发高级副总裁　Xiaozheng Lu  的文章（12页之后的部分）在下面的网址有比较具体的翻译，图文并茂，有心看得进书的人可以看看，是不是传输中采用了什么更高更新可以拿诺贝尔奖的技术可以摆脱传统的用脉冲上升沿或下降沿来传输数据的方法！？哈哈。
http://www.infoavchina.com/html/Integration/2007-12/28/11_05_38_819.html

[ 本帖最后由 notrueccf 于 2008-8-23 03:22 编辑 ]

notrueccf

洗完澡等头发干，再来几句废话。
数字通信总线技术从最早的RS232到RS485、I2C、CAN BUS再到 usb /usb 2.0 ，1394 ,Lan ，HDMI......？经历这么多代的发展，速度从原来的几十kbps到现在的几Gbps，增长了几万倍，那么，他们的传输线制造技术是否需要同样倍数的技术难度或者制造成本？
剖开这些线材大家都可以看到，没什么特别的！数字总线的“提速”从来都不是依靠线材技术。除了HDMI、Lan、232/485这几种规格需考虑电磁场分布对线芯的走法/绕法稍有要求之外，其它没任何特别，线还是几分钱一米的导线，也不需要什么特殊的保护层，屏蔽层，不需要包金包银。换而言之，用20年前的材料和工艺就可以生产出合格的HDMI线！成本也高不到哪里去。

半导体技术的进步是数字总线速度提高的原因，线材的技术规范和规格是结果，搞反了就是舍本逐末。----还是那句话，好马配好鞍，好器材配好线是应该的，但神化就不对了。

[ 本帖最后由 notrueccf 于 2008-8-23 04:16 编辑 ]

xtal

原帖由 九十九龙马 于 2008-8-23 02:04 发表



那我用PC通过HDMI传输纯黑色的图片到显示器显示 有机会能看到黑底上出现的亮点吗  我刚才试过了一下看了半分钟 没有发觉任何的亮点  证明误码率不是想象中的那么高 估计这个概率很小很小很小

误码率和线材质量 长度,发送单元 接收单元都有关系.
短距离误码率会大大下降.
高质量的发送单元 接收单元 也会大大减少误码率

PS 如果真的想大幅度减少长线传输的误码率.
去买电缆均衡器做中继会更加有效.
在标准发送单元 标准接收单元 标准电缆下
那个东西可以把传输距离提高到30米
(注意,只是标准,不是极品哦)

PS HDMI DVID 使用的是相同的I/O技术:TMDS

九十九龙马

原帖由 notrueccf 于 2008-8-23 02:58 发表
呵呵，那是ECC内存，只有服务器和专业工作站才用（比如你们公司的图形工作站），因为ECC内存不但贵而且速度慢，一般是不用的。现在的技术普通PC就可以把FSB做到800M，普通PC是没有校验的，事实上完全没有问题，只要主 ...

呃 有了中文翻译就明白了 谢谢

“数字视频信号的表现与模拟视频信号存在着本质的不同。数字视频信号随着传送的电缆线长度的增加——在一定的距离范围内，人眼看到的画面质量可以一直保持很好的水平。但当超出这一距离限制时，画面要么完全看不清楚，要么完全失踪。”
看来线材生产厂家和广大有知识的网友看法一致 线要么不通 通了的情况下人眼看到的效果就会一样


“类似的，高质量HDMI电缆线和低质量HDMI电缆线在到达“峭壁效应”点之前都是合格的，但是它们在具体传送信号的性能表现方面却存在着差异，尽管这些差异人眼并不能够辨别出来。”
嗯 线材生产厂家和广大有知识网友的正常眼睛都不能分辨出差异 当然也从不同的方向辩证了非正常人类不用眼睛都能看出极大画面风格变化的可能性


[s:14] [s:14] [s:14] [s:41] [s:41] [s:41] 还不同方向都有极大画面区别？ 风格？ 很高的一个平衡？ 立体感很丰富？  哈哈 笑死了 自刎去吧[s:99]

[ 本帖最后由 九十九龙马 于 2008-8-23 11:08 编辑 ]

九十九龙马

原帖由 xtal 于 2008-8-23 09:05 发表

误码率和线材质量 长度,发送单元 接收单元都有关系.
短距离误码率会大大下降.
高质量的发送单元 接收单元 也会大大减少误码率

PS 如果真的想大幅度减少长线传输的误码率.
去买电缆均衡器做中继会更加有效.
...

那今晚我再试试用投影看纯黑画面是否能看到亮点
家里的HDMI线10米 但由于没吊顶开槽难度大强弱电穿同一根管子 所以买了根相对屏蔽层更好的HDMI线 具体价格忘了大概是500元左右
如果在这么长并缠绕着220电线的情况下都很难看出噪点 我相信在普通的电磁环境下会有非常低的概率看到！

xtal

原帖由 九十九龙马 于 2008-8-23 11:02 发表


那今晚我再试试用投影看纯黑画面是否能看到亮点
家里的HDMI线10米 但由于没吊顶开槽难度大强弱电穿同一根管子 所以买了根相对屏蔽层更好的HDMI线 具体价格忘了大概是500元左右
如果在这么长并缠绕着220电线的 ...

你分辨率多少?
如果是720P 10米当然不会有事.
PS ,我现在等着看HDMI1.3的笑话.
如果是10位色深 60HZ逐行刷新,
那么在5米电缆下几乎没有任何一个显卡公司能活了

九十九龙马

噢 1080P  8位 不过刷新率可以调整到120HZ逐行  投影支持
怪不得我一直苦苦等待的1.3的显卡迟迟不见上市就是因为这个原因吗

[ 本帖最后由 九十九龙马 于 2008-8-23 11:13 编辑 ]

xtal

HDMI  DVID的TMDS时钟频率计算公式如下
时钟频率=水平分辨率*垂直分辨率*1.06*60*(发色数/8)
比如常见的宽屏幕显示器(1920*1200)
时钟频率=1920*1200*1.06*60*(8/8)=146.5344MHZ
而1920*1080(也就是标准的FULLHD分辨率)下 60HZ 10位色深
时钟频率=1920*1080*1.06*60*(10/8)=164.8512MHZ
数据通道的波特率是TMDS时钟频率的10倍

而现在的情况下是怎么样的?
DVID的标称分辨率是指标准的接收设备配合标准5米电缆下误码率合格的分辨率

绝大多数显卡,都只敢标柱1600*1200
标柱1920*1200的显卡极少

从前面的计算可以得出

现有绝大多数显卡连146MHZ都很难搞定,
你让他们怎么搞定165MHZ??

HiViUser

原帖由 notrueccf 于 2008-8-22 23:43 发表
一边看电影一边输的英文，懒得这么较真。monster cable 第一次写的时候是对的，第二次写的时候发现写错也就懒得改了。之所以写英文就是给你们这些港灿看的，喜欢不懂装懂的假洋鬼子，扮野就得，得个讲字，说到基本理 ...

如阁下的英文这样了得，也不想浪费时间去翻譯，

既然你是死硬书院派人仕，只愿花时间求理論，而不作最简单但真实使用性能及效果比較！

HDMI, as we've pointed out elsewhere, is a format which was designed primarily to serve the interests of the content-provider industries,not to serve the interests of the consumer.

The result is a mess, and in particular, the signal is quite hard to route and switch, cable assemblies are unnecessarily complicated, and distance runs are chancy.

Why is this, and what did the designers of the standard do wrong? And what can we do about it?

[s:18][s:18][s:18]

[ 本帖最后由 HiViUser 于 2008-8-23 12:28 编辑 ]

HiViUser

How the designers of the HDMI standard screwed up, and what's to be done about it.

The story begins with another badly-developed standard, DVI. A few years ago, there was a movement within the computer industry to develop a new digital video display standard to replace the traditional analog VGA/RGBHV arrangement still found on most computer video cards and monitors. Interested parties grouped together to form the Digital Display Working Group (DDWG), which developed the DVI standard.
DVI had all the earmarks of a standard designed by committee, and it remains one of the most confusing video interfaces ever. DVI could run analog signals, digital signals, or both, and it could run digital signals either in a single-link configuration (in a cable using four twisted pairs for the signal), or in a dual-link configuration (using seven). Identifying which DVI standard or standards any particular device supported was not always easy, and the DVI connector came in various flavors and was never really manufactured in any form that wasn't well-nigh impossible to terminate.


But the worst thing about DVI was something that the computer-display professionals involved in its development really didn't give much thought to: distance runs. Most computer displays are mounted at most a few feet away from the CPU, so it didn't seem imperative that DVI work well over distance. This lack of concern for function at a distance, coupled with common use of twisted-pair cable(e.g., CAT 5) in computer interconnection, led to a decision that DVI would be run in twisted-pair cable.

Had the DVI standard been designed by broadcast engineers rather than computer engineers, things probably would have turned out very differently. In the broadcast world, everything from lowly composite video to High-Definition Serial Digital Video is run in coaxial cables,and for good reasons, which we'll get to in a bit. Long-distance runsof VGA, in fact, are always handled in coaxial cable (though there may be a number of miniature coaxes in a small bundle, rather than something which obviously appears to be coax).


DVI lacked a couple of things which the consumer audio/video industry wanted. It was implemented on a variety of HD displays and source devices, but it was confusing for the consumer because of the many variants on the standard and different connector configurations,and it didn't carry audio signals. A consortium to develop and promote a new interface, HDMI, was formed; the idea was to come up with a standard which could be implemented more uniformly, was less confusing,and offered the option of routing audio signals along with video.

Here, again, was an opportunity to avoid problems. The difficulties of running DVI-D signals over long distances were well known, and the mistakes of the past could have been avoided by developing HDMI as awholly new standard, independent of DVI. Instead, the HDMI group elected to modify the DVI standard, using the same encoding scheme andthe same basic interface design, but adding embedded audio and designing a new plug. Instead of many DVI options, analog, digital,single and dual link, there was one "flavor" of HDMI (actually, thereis also a dual-link version in the HDMI spec--but you won't find it implemented on any currently available device). This provided the advantage of making HDMI backward-compatible with some existing DVI hardware, but it locked the interface into the electrical requirements of the DVI interface. Specifically, that means that the signals have tobe run balanced, on 100 ohm impedance twisted pairs.

[s:18][s:18][s:18]

[ 本帖最后由 HiViUser 于 2008-8-23 12:19 编辑 ]

HiViUser

We're often asked why that's so bad. After all, CAT 5 cable can run high-speed data from point to point very reliably--why can't one count on twisted-pair cable to do a good job with digital video signals as well? And what makes coax so great for that type of application?


First, it's important to understand that a lot of other protocols which run over twisted-pair wire are two-way communications with error correction. A packet that doesn't arrive on a computer network connection can be re-sent; an HDMI or DVI signal is a real-time,one-way stream of pixels that doesn't stop, doesn't error-check, and doesn't repair its mistakes--it just runs and runs, regardless of what's happening at the other end of the signal chain.

Second, HDMI runs fast--at 1080p, the rate is around 150Mega pixels/second. CAT5, by contrast, is rated at 100 megabits per second--and that's bits, not pixels.

Third, HDMI runs parallel, not serially. There are three color signals riding on three pairs, with a clock circuit running on thefourth. These signals can't fall out of time with one another, or with the clock, without trouble--and the faster the bit rate, the shorter the bits are, and consequently the tighter the time window becomes for each bit to be registered.

Consider, by contrast, what the broadcast world did when it neededto route digital video from point to point. The result was HD-SDI, high-definition serial digital interface. One coaxial cable can route an HD SDI signal hundreds of feet without errors, with no repeater hardware or EQs in the line. Had the consumer industry opted for a coaxial-based standard, we'd be able to do the same in our homes. Admittedly, few of us need to make 300-foot runs; but the ability to run 300 feet without problems would be accompanied by rock-solid certainty of being able to do 50, or 75, without any worry at all.

But why is there such a big difference between twisted pairs and coax? It all has to do with the electrical properties of the two methods of routing signal from one place to another: balanced, through twisted pair, and unbalanced, through coax.

[s:15][s:15][s:15]

[ 本帖最后由 HiViUser 于 2008-8-23 12:22 编辑 ]

HiViUser

We tend to assume, when thinking about wire, that when we apply asignal to one end of a wire, it arrives instantaneously at the other end of that wire, unaltered. If you've ever spent any time studying basic DC circuit theory, that's exactly the assumption you're accustomed to making. That assumption works pretty well if we'retalking about low-frequency signals and modest distances, but wire and electricity behave in strange and counter intuitive ways over distance,and at high frequencies. Nothing in this universe--not evenlight--travels instantaneously from point to point, and when we apply avoltage to a wire, we start a wave of energy propagating down that wirewhich takes time to get where it's going, and which arrives in a different condition from that in which it left. This isn't important if you're turning on a reading lamp, but it's very important in high-speed digital signaling. There are a few considerations that start to cause real trouble:

1. Time: electricity doesn't travel instantaneously. It travels at something approaching the speed oflight, and exactly how fast it travels depends upon the insulating material surrounding the wire. As the composition and density of that insulation changes from point to point along the wire, the speed of travel changes.

2. Resistance: electricity burns up in wire and turns into heat.

3. Skin effect: higher frequencies travel primarily on the outside of a wire, while lower frequencies use more of the wire's depth; this means that higher frequencies face more resistance,and are burned up more rapidly, than lower frequencies.

4. Capacitance: some of the energy of the signal gets stored in the wire by a principle known as "capacitance," rather than being delivered immediately to the destination. This smears out the signal relative to time, making changes in voltage appear less sudden at the far end of the wire than they were at the source. This phenomenon is frequency-dependent, with higher frequencies being more strongly affected.

5. Impedance: if the characteristic impedance of the cable doesn't match the impedance of the source and load circuits, the impedance mismatch will cause portions of the signal to be reflected back and forth in the cable. The same is true for variations in impedance from point to point within the cable.

6. Crosstalk: when signals are run in parallel over a distance, the signal in one wire will induce a similar signal in another, causing interference.

7. Inductance: just as capacitance smears out change sin voltage, inductance--the relationship between a current flow and an induced electromagnetic field around that flow--smears out changes in the rate of current flow over time.

[s:30][s:30][s:30]

[ 本帖最后由 HiViUser 于 2008-8-23 12:27 编辑 ]