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加入日期: Dec 2000 您的住址: 木柵動物園
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引用:
1.這是一個關鍵，很多人以為數位是仙丹，卻不知數位是建構在類比環境上 2.ARQ機制才得以成立這個觀點;雜訊一直都在，只是數位傳輸可以盡量不受雜訊干擾 3.HDMI TMDS視訊數據週期我記得是沒ECC，BER大於10的負9次方，畫面可能就會出現瑕疵 4.有些人認為數位影像傳輸錯誤應該看起來是馬賽克畫面破損，這是一個數位無線電視與電腦壓縮影像檔造成的誤會。TMDS並沒有壓縮...所以不要因為數位兩個字，誤以為數位出錯都會是一樣的情形。 回到正題，前面提過了數位實際上是在類比環境上跑，訊號數位化就是為了降低類比環境的干擾與訊號衰減問題，那數位傳輸為何還會傳錯產生畫面問題呢？因為干擾跟訊號衰減導致BER超過容忍值阿，類比稱這是雜訊，數位化這就不算雜訊嗎。 6.草莓棉花糖 附上一些圖給有興趣的人參考 類比傳輸訊號遞減  數位傳輸懸崖效應，超過容許範圍就跳崖了  線越長衰減越大傳輸頻寬越小  加入error rate有沒有越看越有趣   眼圖判斷  
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2013-01-08, 10:30 AM
#41
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Elite Member
= PCDVD認證賣家 =
加入日期: Apr 2001 您的住址: 死老百姓
文章: 4,824
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短的真的沒差，試過很多條，連對岸平板附的一條NT50的那種爛線，畫質一樣....，但長一點就有差。
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2013-01-08, 10:36 AM
#42
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*停權中*
加入日期: May 2005
文章: 345
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長見識了，原來高級線材到了數位時代還是有用的。
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2013-01-08, 10:46 AM
#43
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Elite Member
加入日期: Mar 2003 您的住址: Vancouver, Canada
文章: 15,006
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引用:
也不能這樣說 要正確説法（給普通人） 多長的電線 就需要配多粗的電線 http://www.monoprice.com/home/home.asp?pn=help&idx=12 HDMI® Cables - AWG Explained A cursory examination of the Monoprice HDMI Cables pages will reveal that there are more choices than just Standard and High Speed. What is likely to jump out at you are the different AWG (American Wire Gauge) ratings of the different cables. There are 28 AWG High Speed HDMI Cables and 22 AWG Standard HDMI Cables. What does all this mean? First, AWG (American Wire Gauge) is a measure of the thickness, or gauge, of a wire. The system is based on the number of times a wire could be wound around a spool of a given width, so a 30 AWG wire could be wound 30 times, while a 20 AWG wire could handle only 20 windings. Therefore a 20 AWG wire is thicker, with a larger diameter, than a 30 AWG wire. Wire gauge directly relates to the amount of electrical current that can be carried on the wire. The larger diameter of wire, the more current it can carry. In terms of HDMI this means that a larger gauge wire (smaller AWG number) is capable of higher bandwidth than a smaller gauge (larger AWG number). Therefore, a 22 AWG wire is capable of higher bandwidth than a 28 AWG wire. If you look closely at the HDMI Cables pages, you will see that there are cutoff points for High Speed HDMI Cables in each AWG grouping. Beyond the cutoff the cables of the same AWG are rated as Standard HDMI Cables. The longer cables are not made any differently, however. As the length of a wire increases, so does the overall resistance of the wire. Increased resistance means decreased current capacity and therefore decreased bandwidth in HDMI terms. The cutoff points for High Speed HDMI Cables of each AWG rating are: 28 AWG = maximum 10 feet 26 AWG = maximum 12 feet 24 AWG = maximum 15 feet 22 AWG = maximum 25 feet So a 12 foot 28 AWG HDMI Cable is not rated for the full 10.2 Gbps required for the High Speed designation. However, it doesn't just jump down to the minimum 2.25 Gbps required for Standard HDMI Cables. It may be capable of 9.5 Gbps, which is almost enough for the High Speed rating, but because it isn't 10.2 Gbps, it must therefore be classified as a Standard HDMI Cable. The longer the wire, the lower the bandwidth it will be able to handle. However, all of our HDMI Cables are capable of at least the 2.25 Gbps minimum required for Standard HDMI Cables. 從另外一個角度來看 如果 25ft + 25ft 然後中間可以加一個 Repeater 訊號會比較好 跟一條 普通 50ft 比較 |
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2013-01-08, 11:00 AM
#44
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Advance Member
加入日期: Dec 2002 您的住址: 超時空世紀
文章: 390
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我們公司就做這種線的測試器,但...只是測通不通而已
 只要該有的都有,短線訊號不會太差, 但就是有測過隔離線偷料的線,裡面有好幾條包覆線都沒了 
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和田加奈子: あの空を抱きしめて ; 不確かなI LOVE YOU Something touched me deep inside The day The music died |
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2013-01-08, 01:22 PM
#45
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Elite Member
加入日期: May 2002 您的住址: 板橋
文章: 5,112
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引用:
線的雙絞/屏敝沒做好,板子怎麼改也沒用吧----除非讓輸出波形預先衰減到不至於產生太多EMI/RFI的地步,不過這麼一搞另一端的設備解的出來才有鬼 ....
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士大夫之無恥,是謂國恥  ....
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2013-01-08, 01:35 PM
#46
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Master Member
加入日期: Dec 2001 您的住址: 台中縣
文章: 1,704
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引用:
再次聲明小弟是外行人...有誤請大家不吝指正。 如果是一般資料傳輸的話，遇到ECC沒辦法校正的部分應該就會要求重傳，超過協定 容許的時間應該就會向上層回報錯誤，就像我們從網路拖回來的影片不會帶有線材受到 干擾所造成的錯誤一樣。 數位傳輸應該也只是把類比訊號處理過將之判別為0或是1，若是中間夾雜的驗證機制 發現資料產生錯誤，或是訊號受到干擾無法辨識，應該會有相對應的處理方式， 訊號即便受到雜訊干擾，但最終應該也只有正確的0、正確的1，無法判別， 而不應該會出現明明應該是0的資料，判斷成1也向上層回報。 但我想影音傳輸不需要做的如此嚴謹 (這點您也提到了)，而且資料有時效性， 沒必要遇到畫面中有錯誤在時間內無法校正就整張圖不顯示。但數位資料和 類比訊號完全不同，因雜訊產生的錯誤在意義上應該是不一樣才對。 6. 草莓棉花糖 查了一下聲優陣容十分堅強，有機會也來朝聖一下∼
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Ryzen 5 2600X & ROG STRIX X370-F Kingston ECC U-DIMM DDR4-2666 16GB * 2 Gigabyte CV27F & MSI RX560 AERO 4G OC Cooler Master V750 Gold Fractal Design Define R6 CREATIVE GigaWorks T20II |
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2013-01-08, 02:13 PM
#47
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*停權中*
加入日期: Oct 2010 您的住址: 四季如夏的地方
文章: 2,596
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講到AWG的問題，細線的AWG不可能小，可是很粗的線也不見得AWG就小，以前有發現過有些廠商推出一些看起來很粗的線就是靠著外頭膠皮誤導消費者.
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2013-01-08, 02:39 PM
#48
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Elite Member
加入日期: Mar 2003 您的住址: Vancouver, Canada
文章: 15,006
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引用:
你在說那個愛告人的公司啊 我家裏有好幾條它們家裏的 Speaker Wire.... 就是有這樣的情形  |
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2013-01-08, 03:05 PM
#49
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Basic Member
加入日期: Nov 2003 您的住址: 台北土城∼∼
文章: 12
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引用:
有試過換條HDMI cable看有改善嗎？ 如果你沒有接HDMI之前就有這問題，應該是原來訊號問題，或者是電視機、電視盒問題... |
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2013-01-08, 05:22 PM
#50
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