小弟無聊自己翻譯過了.....(翻譯完才發現對岸有人翻譯過了 囧) 翻的很爛請見諒 原文網址 請自己對照文圖 http://www.cdfreaks.com/reviews/Why-DVDRW-is-superior-to-DVD-RW.html ---------------------------- Article Why DVD+R(W) is superior to DVD-R(W) Date June 2003 Author Michael Spath Since the war between DVD+R(W) and DVD-R(W) started, several comparisons of the two formats have been published, but none of those I read did contain really accurate technical information. Instead, journalists relied on public press releases and white papers provided by vendors to write their articles, resulting in the end into superficial explanations and sometimes contradictory conclusions. 自從DVD+R(W)跟DVD-R(W)陣營開始大戰，許多廠商發佈了這兩種格式的資訊，但我並沒有 從其中真正的了解到實際的技術細節。然而，記者依靠廠商發佈的這些資訊來寫新聞，導 致了膚淺與矛盾的結論。 The main problem here is that getting DVD+R(W) and DVD-R(W) standards require money and NDAs, so that little detailed technical information about these formats can be found on the Internet. This is very unfortunate, as it prevents both journalists and techies from all over the world to independently review, compare and choose the best format by themselves. 主要的問題是在於取得DVD+R(W) 與DVD-R(W) 標準內容需要金錢與簽署不公開協定(NDAs) ，所以能在網際網路上找到的格式細節內容少之又少。這是令人遺憾的事，使的記者與資 訊使用者無法自主而獨立的比較與選擇最適合他們的格式。 Because they cannot access the technical details (or simply due to laziness), some people prefer to carefully conclude that there's no real technical difference between the two formats, and that if you forget all the marketing propaganda + and - are equally good. To me this is an evidence that such people have not understood (or more probably not even read) the format specifications. 正因為她們無法取得技術的細節，一些人仔細推斷後傾向認為這兩種格式並沒有實際的差 異，不在意行銷宣傳的話+與-是同樣的好。對我而言，這意味這人們並不了解，或沒有仔 細分辨這兩種格式的差異。 After having studied the two formats I found that there are several fundamental differences between them, and I concluded that + is superior to -. The goal of this paper is to present the technical details from the specifications that led me to this conclusion, so that anyone with basic engineering knowledge can make his own opinion. This article is by no mean exhaustive, and some exclusive + and - features (e.g. CAV writing or copyright management) are not tackled here because I considered them less significant. Note that this article is pretty technical, so some understanding of optical storage technologies is required. 在研讀這兩種格式後，我發現這兩者有幾個基本上的差異，而且我推斷認為+比-好。這份 報告的技術細節是由我所下的結論，所以只要任何人有基本的資訊工程背景，可以自己下 判定。這份文件並不保證徹底無疑，+R 與-R 的專屬功能 (例如定角寫入或版權管理) 也 沒有做比較，因為我認為那些部分並不重要。由於這份文件十分的技術性，所以讀者需要 了解一些光學儲存裝置的技術。 Pre-pits versus ADIP 預刻反射坑對上ADIP To help its recording, a blank disc usually gives 3 kind of information to the drive : tracking (so that the pits are correctly written along a track), addresses (so that the drive can write at the good location) and speed (so that the disc is spinned at the correct velocity). With CD-R(W), tracking and speed information are carried by the wobble, while addresses are contained in the ATIP data (Absolute Time In Pregroove, a frequency modulation of the wobble). 為了幫助燒錄，空白光碟通常會提供三種資訊給燒錄機：軌道(使反射坑可以正確的沿著 軌道寫入)，位址(使燒錄機可以寫入正確的位置)與速度(使碟片旋轉正確的速率)。在 CD-R(W)，當位址包含了ATIP資料(將絕對時間放在預溝槽裡，這是一個擺動的調變頻率) ，軌道與速度的資訊由擺動提供。 DVD-R(W) format uses a slow wobble (140,6kHz) for tracking and speed, and the addressing (and additional) information is carried by the land pre-pits (pre-recorded pits between grooves). On the groove signal, pre-pits give amplitude spikes. DVD-R(W) 格式在軌道與速度上使用低擺動頻率(140.6kHz)，位址(與其他)資訊則由陷落 預置反射坑(LPP，land pre-pits)，在溝槽間預錄的反射坑提取。在溝槽上的訊號，預刻 反射坑產生擴大的波尖峰。 DVD+R(W) format uses a much faster wobble (817,4kHz), and the addressing (and additional) information is carried by a phase modulation of this wobble called ADIP (ADdress In Pre-groove). DVD+R(W)使用較快速的擺動頻率(817,4kHz)，這種由擺動的相位調變來提取位址(與其他) 資訊的方式則叫做ADIP (位址直接放置在預溝槽裡)。 　 As taught by signal theory, the phase modulation method has a better noise immunity than the pre-pits method, and therefore ADIPs are generally more robust than LPPs against all external disturbances (electrical noise, disc tilting, focusing problems, etc). Apart from the usual sources of noise in a drive, a particularly annoying example of this problem occur when you are burning data on a DVD-R(W) and try to read the pre-pits information at the same time : because the light emitted by the burning laser is interfering with the reading beam, correct pre-pits detection is much more difficult to achieve, which can jeopardize linking precision. 有如訊號學所教的，相調變方式對於雜訊的免除能力優於預刻反射坑方式，因此ADIPs方 式比起LPPs方式通常更加能對抗外來的干擾(電子雜訊，碟片傾斜，對焦失準等)。要從裝 置中將有用的資料跟雜訊分開，舉一個惱人的實際例子，就是當你燒錄資料DVD-R(W)以及 同時試著讀取 預刻反射坑資訊會發生：因為雷射燒錄光線的射出與讀取光束相牴觸，使 的預刻反射坑的正確偵測變的更加困難，也影響到精密度。 But the pre-pit technology is not only a weakness against noise, it also becomes a limiting problem as the speed of the disc increases, because at high speeds pre-pits are more difficult to detect than phase inversions. Indeed, on the wobble signal the pre-pit information only exist where the pre-pit is located in time, while the information of phase inversion is spread over the complete inverted period of wobble (or more, actually as long as the phase is not inverted again). According to the specifications, the minimum length of a DVD-R(W) pre-pit is 1T (1/26.16E6 s), while a DVD+R(W) wobble period lasts 32T, which makes it much easier to detect. 而且預刻反射坑技術不只抵抗雜訊的能力較差，還會造成碟片增加速度的阻礙，因為高速 時比倒相式技術更難偵測。當然，在擺動訊號上，預刻反射坑資訊只存於 預刻反射坑所 在的位置，而相倒置則會展開至完成擺動的期間。(或更多，因為事實上相位並沒有倒置 回來)。DVD-R(W)規範上最小的預刻反射坑長度為1T( 等於2616000分之1秒)，而DVD+R(W) 的持續擺動期間為32T，所以後者較容易被偵測。 Another bad side effect of this pre-pits method is that DVD-R(W) mastering is made more difficult than with DVD+R(W), since a higher precision is required to cut both the grooves and the pre-pits between them. Special dual-beam recorders are usually required for - stamper mastering, although some manufacturers now also use single beam cutting. 預刻反射坑的另外不良影響，就是使DVD-R(W)的後製比DVD+R(W)更加的困難，因為切割溝 槽與預刻反射坑時需要更高的精密度。通常會需要使用特殊的雙光束燒錄器來進行後製打 印 ；儘管現在一些廠商現在只使用單光束切割。 Not only are the pre-pits more error prone than phase modulation, but data they carry are also less protected. In one ECC block pre-pits carry 192 bits of information (one pre-pit block). Out of these 192 bits, 48 are not protected by any error correction mechanism, 24 bits are protected by 24 bits of parity (A parity), and the last 56 bits are also protected by 24 bits of parity (B parity). All in all, this strange heterogeneous structure finally gives a pretty weak protection to the information bits carried by pre-pits. 預刻反射坑不只比相調變傾向於有更多的錯誤，被攜帶的資料也缺於保護。在一個ECC Block(錯誤偵修區塊)中，預刻反射坑含有資訊的192位元(一個預刻反射坑區塊)。超過 192位元的部份，48位元並未受到任何錯誤修正演算法，24位元由24位元的同位法(A同位 法)保護，以及最後56位元由24位元同位法(B 同位法)保護。總而言之，混種的保護結構 使的預刻反射坑對於資訊的保護是糟糕而貧弱的。 On the other hand the corresponding DVD+R(W) structure is 4 times smaller : one ADIP word is 52 bits large, consisting of 1 sync bit, 31 data bits and 20 parity bits (which protect all data bits). One ECC block contains 4 ADIP words, so 204 bits of information in total. Also each ADIP word contains the full ECC block address, while 4 times this size are needed in the - technology to extract this address : this gives significant speedups when seeking uses this method. 另一方面，DVD+R(W)的對應結構小了四倍：一個ADIP 字元組是52位元大小，一個同步位 元組成，31個資料位元與20個同位檢查位元(保護所有的資料位元)。一個ECC Block包含4 個ADIP字元組，所以資訊總共是204位元。每個ADIP字元也包含完整的ECC Block位址，當 展開後存在著需要的四倍長度，因此這個方法顯著的提升了速度。 Defect management and recording quality 瑕疵管理與燒錄品質 Another major advantage of DVD+RW format over DVD-RW (although no drive support it yet) is hardware defect management provided by the DVD+MRW standard (Mt Rainier for DVD+RW). On a DVD+MRW disc, when an error occur during a read or write access to an ECC block, this block is flagged as bad and the drive will not use it any more. Instead, when writing to the disc, data which should have been stored in this bad block are relocated elsewhere ; likewise, when the drive is asked to read these data again, it will fetch them from the new location. These operations are completely transparent for any software (whatever operating system, driver or burning application is used), and while the initiator is requesting consecutive sectors the drive will actually read data from various locations : this new abstraction layer is called Logical to Physical address translation. 另一個DVD+RW 優於DVD-RW (僅管撰寫本文時還沒有對應的燒錄機) 的地方是硬體瑕疵管 理是由DVD+MRW標準 (Mt Rainier 於DVD+RW)。當在DVD+MRW上讀寫一個ECC區塊而發生錯 誤時，這區塊會被標示為損毀，而不再使用它。也就是當資料寫入碟片損壞區時，會被重 新分配至別的地方，而讀取時則會由被分配到的地方來讀取。這些動作對於所有的軟體( 乃至作業系統，驅動程式或燒錄軟體) 都是完全隱形的，實際上當需要讀取連續的扇區資 料時，裝置將從各分散的地方讀取資料：這個新的概念層次叫做 "邏輯對實體位置轉譯" 。 As a side note, popular belief is that defect management is only useful when burning new discs (where data which are being written can also be read back, checked and moved to another location if needed), but that it is helpless on discs which get damaged after they have been burned. This is wrong, because when an ECC block is partially damaged and requires several retries to be read (or for instance give too many PI/PO errors), these data can proactively be moved to another clean location on the disc before media wear-out makes them unreadable. Of course, if an ECC block is damaged beyond error correction capabilities, data are definitely lost ; however, only very serious damages can make such a thing happen, as PI/PO correction can handle burst errors larger than 6 mm. 有如一個邊註，一般的看法是，只有在燒錄新的碟片的時候(或資料搬移，再燒錄時)有使 用瑕疵管理。不過這對於碟片在燒錄完成後才造成的損壞無可奈何。這是不正確的，因為 有部份ECC區塊損壞而需要許多的重試讀(或得到太多PI/PO)時，那些資料可以在媒體老化 而導無法讀取前，前瞻性的搬移到碟片上其他乾淨的區域。當然，如果ECC區塊已經損毀 超過可以修正的能力，資料就肯定會流失了。不管怎樣，那是非常嚴重的損毀才有可能發 生，像PI/PO可以修正滿達6公厘的錯誤。 As with formatting, DVD+RW standard enables background verifications, i.e. the disc is checked for defects when the drive is idle. Of course, at any time the user can still read or write to the disc, or eject it from the drive ; background verification would then resume later from where it was stopped. Combining these features together gives a very powerful system which can continuously try to improve the longevity of discs : while the user performs its usual operations, the drive can check in the background the complete surface of the disc and move data from damaged locations to clean areas. Such advanced use of defect management are already described in the DVD+MRW specification, for instance with the Self Monitoring Analysis and Reporting Technology (SMART, a technology inspired from hard discs). Finally, it is important to mention that DVD+MRW provides full read-only compatibility for players which don't understand MRW. DVD+RW的標準將啟用背景驗証功能，好比光碟機在碟片閒置時檢查瑕疵。當然，任何時候 使用者還是能夠讀寫或退出碟片；背景驗證將會在稍後繼續進行。將這些功能集合起在一 起，成為一個使碟片壽命不斷延長的強力系統。使用者只要一如往常的使用碟片，光碟機 會在背景自動將資料從發生損壞的區域移往乾淨的區域。這類的先進瑕疵管理已被 DVD+MRW規範列入，並產生自我監測分析技術的建議(Self Monitoring Analysis and Reporting Technology S.M.A.R.T，來自硬碟的技術)。最後，必須要表揚的是DVD+MRW完 全提供唯讀相容，甚至播放器不需要知道MRW。 Although DVD-R(W) also support some defect management (Persistent-DM and DRT-DM), it is mainly software based and actions must always be initiated by a specific program. Furthermore, since DVD-RW format lacks the needed structures, address translation has to be performed also by software, and translation tables have to be stored on the user area of the disc according to a higher level specification (for instance in the sparing tables of UDF 2.0). This makes DVD-RW not well suited for simple file storage or image burning, as it requires a complete file system to benefit from defect management. Note also that although DVD-RW cannot use +MRW technology (due to technical differences), DVD+RW can very well use UDF 2.0. 儘管DVD-R(W)也支援一些瑕疵管理(Persistent-DM 與 DRT-DM)，但這主要是以軟體為主 ，必須使用特殊的程式去起始。而且由於DVD-RW格式缺少需要的結構，位置轉譯是由軟體 完成，而且轉譯表必須與儲存於使用者資料區，對應到較高階的規範(好比UDF 2.0的節約 表)。這使的DVD-RW不適於單純的檔案儲存或影像燒錄，而需要檔案系統去幫助瑕疵管理 。然而儘管DVD-RW無法使用+MRW技術(技術不同)，DVD+RW卻可以完好的使用UDF 2.0。 Also a DVD+R(W) disc allows a drive to achieve better writing quality (independently of media quality), because it gives more information to a drive than a DVD-R(W). Indeed, just like with CD-R(W), the best writing settings for a given disc are found at startup during the OPC (Optimum Power Control) algorithm, which use data contained in the pre-pits blocks/ADIP words. And regarding OPC, a DVD+R(W) gives not only more information (e.g. power dependency on wavelength) but also more precise ones (e.g. startup laser power). Moreover, all these information are available for 4 different speed ranges (primary and upper speeds, normal and 4x+ mode), while - format only provides one set of data. This is very important because optimal writing settings are very sensitive to burning speeds. Also the OPC test area of DVD+ is 32768 sectors in total, compared to 7088 sectors for DVD-. DVD+R(W)碟片也允許燒錄機達到較好的寫入品質(媒體的獨立品質)，因為燒錄機從它獲得 比DVD-R(W)更多的資訊。好比CD-R(W)，給碟片的最佳的寫入設定可以在一開始的OPC(最 佳化工率控制)進行時找出來， 在那些預刻反射坑區塊/ADIP字元使用已設置妥當的資料 。以及就OPC而論，DVD+R(W) 不但給予更多的資訊(如在波長上的功率依靠度)，也更加明 確(如起始雷射功率)。此外，這些資訊對於四種不同的速度範圍(基本，快速，一般，與 4X+模式)都是全部有用的，而-R(W)格式只提共一部份資料。這很重要，因為光學寫入的 設定很對於燒錄速度是很敏感的。DVD+ 的OPC測試區有32768個扇區，也勝過DVD-的7088 個扇區。 Linking 鏈結 When for any reason writing on the disc has been stopped and is resumed, new data have to be linked with the old ones. Linking is a very important and tricky task, which can cause various problems both at physical and logical level. First, a short overview of the linking methods used by the two formats is required. 不管什麼原因，當寫入碟片時需要停止與繼續時，新的資料必須與舊的做鏈結。鏈結是一 個非常重要而且難處理的工作，容易在物理與邏輯層面造成許多問題。首先，我們需要總 覽這兩種格式鏈結的方法。 With DVD-R(W), 3 different linking methods can be used : 2K linking, 32K linking, and loss-less linking. In all cases recording has to stop 16 bytes after the first sync of the first sector of an ECC block, and new data are recorded starting between the 15th and the 17th byte of this same frame. The precision of the linking is therefore 2 bytes and the space waste either 2KB, 32KB or nothing (note that loss-less linking method does not work with DVD-R for Authoring). With DVD+R(W), linking is performed in the last 8 channel bits (4 data bits) of an ECC block. Linking precision is therefore 4 times higher and loss-less linking is the only method allowed by the standard, which guarantees no space waste. DVD-R(W) 有三種不同的鏈結方式可以使用：2K鏈結，32K鏈結，以及無損(loss-less) 鏈 結。不論是哪一種，一個ECC區塊的第一扇個區之後有16位元組是停止位元組，而新資料 的寫入則於同一頁框(frame)裡面的第15與第17位元組之間開始。DVD-R(W) 鏈結精密度需 要2資料位元組長，以及浪費空間2千位元組，或32千位元組，或不浪費 (但無損鏈結並無 法使用於DVD-R for Authoring )。DVD+R(W) 的鏈結則是使用一個ECC區塊最後八個通道 位元(4個資料位元)，鏈結的精密度是DVD-R(W) 的四倍高，而且無損鏈結是唯一可以使用 的標準，以確保沒有浪費的空間。 　 Even when loss-less linking methods are used, the pits are not perfectly contiguous on the disc, and therefore some PI/PO errors will always occur : to minimize this effect, the location of the linking region is very important. With -RW, the linking region is in user data, and therefore useful bytes will always be corrupted there. Also since the linking occurs after the first sync, the second sync frame (and possibly the third one) will also be lost, since the sync words will not be correctly spaced in the ECC block. With +RW, the linking region is in the last byte of PI correction, which leaves user data bytes untouched. Also the linking position guarantees that all syncs in the next ECC block will be corrected spaced, which gives at least one sync frame less to correct for the player compared to -RW. Note that with +RW, corrections due to the linking region and corrections due to the sync shift are split between two ECC blocks, while they must all be performed by a single ECC block with -RW. 即使使用無損鏈結，反射坑也無法在碟片上完美的連貫，因此總會造成一些PI/PO錯誤： 為了使這個影響降至最低，鏈結區域的位置是非常重要的。-RW的鏈結區域在使用者資料 區，因此有用的資料總是在這邊損壞。也因此在第一個同步發生鏈結之後，第二個同步頁 框(甚至第三個)也會造成遺失，之後同步指示在一個ECC區塊裡就無法被正確的間隔。+RW 的鏈結區域則是位在PI修正區的最後一個位元組，與資料區無關，也因此確保了下一個 ECC區塊的同步間隔是正確的 ，至少比起-RW，+RW比較不需要校正同步頁框。值得注意的 是，+RW修正鏈結區與同步位移是由兩個ECC區塊所處理，而-RW是由一個ECC區塊完成。 Linking can also cause various troubles at physical level, and when looking directly at the HF signal read by the PUH, the linking region looks like the following: 鏈結也能導致許多物理層面的問題，直接由拾取頭(Pick-Up Head ，PUH)讀取的高頻(HF) 訊號，鏈結區看來像是這樣： The slicing level is the digital threshold which separates zeroes from ones, and therefore it must always be centred in the HF signal for good reading quality : when the slicing level deviates too much from its perfect position, the run-lengths (3T to 14T) are wrongly recognized, which causes decoding errors. But as explained previously linking is not perfectly accurate, and therefore a gap will always exist between the two recorded sessions, and the longer the gap, the further the slicing level can drift. Furthermore, between the two linked regions the slicing level can also differ, because of various physical parameters which could have changed between the two recording sessions (laser power, media properties, recording speed, etc) : when this jump is too high, again errors appear. So the smaller the gap and the jump, the better quality and compatibility we get : -RW allows a 32T large linking gap and does not care about this slicing level jump, while +RW allows a 8T large linking gap and a maximum limit for this jump under any condition. This makes +RW loss-less linking also more powerful at physical level. 這個切割水平(slicing level)是用來辨識數位0到1的門檻，因此必須位於HF訊號的中央 ，才能獲得良好的讀取品質：當這個切割水平偏離理想的位置太多， 約有一段長度(3T 到14T) 會被錯誤的辨識，這將導致解碼錯誤。但如之前所說，鏈結不是精準完美的，因 此在兩個燒錄區間，總是會存在間隙，越長的間隙，導致越嚴重的切割水平漂移。再者， 切割水平可能在兩個鏈結區不相同，因為在兩個燒錄區間，許多物理參數會變化(雷射功 率，媒體特性，燒錄速度等)：當跳動太高，錯誤又再發生。所以較小的間隙與跳動，可 以讓我們獲得較好的品質與相容性：-RW 允許32T 大小的鍊結而不在乎切割水平的跳動， 而+RW 僅允許8T大小的鏈結，並在任何條件下有最大的鏈結跳動限制。這也使的+RW 的無 損鏈結在物理層面更有利。 Multiple recording sessions and compatibility 多重燒錄與相容性 If you want to partially record a DVD-R(W) disc and use it immediately, but also want to be able to record more data later, border zones are used, which are meant to make this partially recorded disc compatible with standard DVD-ROM players. So every -R(W) recording session has to start with a border-in area (except the first one, which starts with the lead-in) and stop with a border-out area. 假如你要部份地燒錄DVD-R(W)碟片而且立即使用它，而稍後還要再燒入更多的資料，那就 要使用分界區(border zones)使燒錄好的碟片能相容於標準的DVD-ROM播放器。所以每個 -R(W)燒錄區段皆始於一個入界(border-in)區(第一個區段則是例外，始於導入)，並止於 一個出界(border-out)區。 However, the size of these border zones is quite amazing : 32 to 96 MB for the first zone, then 6 to 18 MB for the next ones. This means that a disc containing 3 recorded sessions can require up to 132 MB (more than 2% of the complete storage capacity) just for separating these regions. Furthermore, the border-out and border-in areas have to be linked together, using one of the 3 methods (and the possible associated problems) explained previously. Note also that for some unknown reason a border-out is needed before the lead-out, while the first border-in is replaced by the lead-in. 然而令人相當吃驚的是：第一個分界區的大小為32到96百萬位元組，接下來的每一個則為 6到18百萬位元組。這意味著一片碟片若包含三個燒錄區段，則光是為了區分這些區域， 就可花費超過132百萬位元組(超過2%的儲存空間)。此外，入界區與出界區使用之前說過 的三種方式的其中之一(與相關可能的問題)鍊結在一起。還要注意的是，由於不知道的原 因，當第一個界入區是由導入(lead-in)區置換時，必須在導出區(lead-out)前放置一個 出界區。 On the other hand, when multiple recording sessions are used on a DVD+R(W) disc, Intro and Closure zones are used (the counterpart of border-in and border-out), but they are always 2 MB large : therefore, with + format, a 3 sessions disc always uses only 4 MB to delimit the regions (the lead-out replaces the last Closure zone). Also a nice feature of multi-sessions implementation on DVD+R(W) is that one can use a session to reserve space, i.e. sectors which are left unrecorded (this blank area is called Reserved Fragment). Thus, additional data can be recorded in next sessions while the first one will only be written later : this can be useful for instance when a precise location on the disc has to contain file system tables, which can only be filled after all the files have been written to the disc. 另一方面，使用DVD+R(W)碟片來燒錄多區段，則使用進入(Intro)區與結束(Closure)區( 有如入界與出界區)，不過他們是固定的2百萬位元組大：因此，使用+格式燒錄三個區段 ，只花費4百萬位元組去界定區域(最後使用導出取代結束區)。還有一個在DVD+R(W)上實 現的好功能，就是可以使用一整個區段做為預留空間，也就是使扇區處於未燒錄狀態(這 個空白區塊叫做已保留片段(Reserved Fragment))。這樣新增的資料就可以跳過並燒錄於 下一個區段，而這個空白區塊可以稍後再寫入：舉一個實用的例子，當檔案系統分配表需 要嚴謹的擺放在碟片上特定的區域時，可以在所有檔案都寫入碟片之後再寫滿它。 Compatibility is a very sensitive topic when comparing the two technologies, but independently of media, recorders and players quality, some logical causes of incompatibility can be noted. Indeed, both recordable formats use values in the lead-in structures which were forbidden or reserved in the first DVD-ROM specification (e.g. disc structure, recording density, etc) and which can cause compatibility failures on some old or particularly picky players. 在比較兩種技術時，相容性是很重要的一個議題，但是媒體的獨立性，燒錄器與播放器的 品質，常見一些不相容的可能原因。當然，這兩種燒錄格式在導入結構中使用的數值資料 是初代DVD-ROM規範(如碟片結構，燒錄密度等)所預留或禁止的，也因此在一些舊型或過 於嚴謹的播放器會導致不相容的狀況。 A famous example of such logical incompatibility is the "Book Type" field, which indicates the type of the disc. The first DVD-ROM specification only allowed 0 (i.e. read-only) to be written there, but later each recordable format defined its own value to identify itself ; unfortunately it turned out that some players simply refuse to read a disc with a non-zero value. To handle this problem, the latest DVD+R standard specifically authorizes to write a zero Book Type for compatibility reasons, and nowadays many drive manufacturers have made this bit programmable. But this cannot be done for DVD-R(W), as the Book Type (with several other information in the lead-in) are pre-embossed (i.e. pre-recorded) on blank media. Note however that although it reduces compatibility, this pre-recorded Book Type also improves copy-protection security, as it enables any player to easily identify a DVD-R(W) disc. 用來辨識碟片種類的 "書入類別(Book Type)" 辨識欄位，有著一個常見的邏輯性不相容 問題。初版的DVD-ROM規範只允許將此設置為0(唯讀)，但較晚出的每一種可燒錄格式都定 義了他們自己的值作為辨識。不幸的是，一些DVD播放器遇到此區為非0值時，就直接拒絕 讀取了。為了解決這個問題，最新的DVD+R規範允許在此欄位寫入0值使其能相容，而且現 在很多燒錄器廠商已經讓使用者可以自由選擇是否啟用這個功能。這無法在DVD-R(W)上面 實踐，因為書入類別(以及很多其他在導入的資訊)是已經在空白碟片上預先刻錄好(在預 錄置時)的。不過雖然因此減少了相容性，預錄置的書入類別卻也增加了拷貝保護的安全 性，因為它使的播放器能輕易的辨識是否為DVD-R(W)碟片。 An additional compatibility risk exist with DVD-(W) in the user data area and is introduced by the 2K/32K linking methods. Indeed, the linking sectors used with these methods must use a special data type to be differentiated from normal data sectors, and this value was not allowed in the original DVD-ROM specification. There's no known study about the impact of this field on compatibility, but sector headers are a vital part of the decoding process, and therefore it is always safer to keep them fully compliant with the strictest DVD-ROM standard. DVD-R(W)在使用者資料區還多了一個相容性的風險，就是採用2K/32K鏈結方式。當然，扇 區鏈結一定是使用一種特別資料型態，而不同於一般資料扇區的鍊結，且不被最原始的 DVD-ROM規格所允許。在這個部份對相容性的影響不得而知，然而扇區標頭是解碼過程極 為重要的一部份，所以嚴格的完全與DVD-ROM標準相容總是比較安全的。 Conclusion 結論 During my study of rewritable DVD formats it seemed very clear to me that DVD-R(W) standard was not as well designed as DVD+R(W) (or even DVD-RAM). And although some serious efforts have been put in the latest revisions of the - format to fix some of the original problems (at the cost of a much increased complexity), it still remains technically inferior to +, due to some intrinsic weaknesses (e.g. pre-pits). This is not very surprising, as Sony and Philips have a much longer experience at defining standards than Pioneer (and several key patents), and they also had the advantage to publish their standards after their competitors. 當我在研習DVD複寫格式時，對我而言很清楚的DVD-R(W)格式不如DVD+R(W)(甚或DVD-RAM) 。 儘管在最後謹慎的再校定-R(W)的資料，以修正一些文章原來的問題(也使的文章更複 雜)，但最後還是在技術本質上輸給了+R(W)格式(如預刻反射坑)。這不令人非常意外，新 力索尼與飛利浦在訂定標準上，比起先鋒有著更多的經驗(與一些關鍵專利)，他們晚於對 手公佈標準也取得一些優勢。 Although the arguments presented in this document might look like technical details to most readers, disc format is what defines the limits of what drives can do with a given medium, both in terms of performances and features. Therefore, the technical advantages of the DVD+R(W) format will with time turn into faster, more powerful and more reliable drives for end users. This is already the case today, and the gap will continue to increase as DVD+R(W) drives will exploit more and more of the advantages of the + format. However, as history showed, the best ideas are not guaranteed to win on technology markets, and only time will tell which format becomes the new standard. 儘管對大多數的讀者而言，這些在文章中的爭論的呈現看起來像是技術細節，碟片格式限 制了燒錄機在性能與功能中，所能達到的平衡點。因此，DVD+R(W)的格式的益處將為使用 者在未來帶來更快速，更有力與更可靠的裝置。這在今日已成事實，DVD+R(W) 燒錄機的 優勢差距將會擴大並拓展越來越多+格式的優點。然而不管如何，歷史表明了最好的理念 不保證能贏得技術市場，只有時間能告訴我們何種格式能成為新的標準。 Acknowledgements (答謝) I would like to thank the engineers from Pioneer Japan and Philips Netherlands who reviewed early versions of this article for their most useful corrections and comments (note that this only means that these people kindly contributed to the technical correctness of the article, not that they - or their company - agree with my conclusions of this article). Also many thanks to J.W. Aldershoff for having suggested and organized these reviews, and for hosting this article. 我要感謝日本先鋒與荷蘭飛利浦的工程師預覽了本文的早期版本，以及提供了寶貴的修正 與建議(僅表示這些工程師好心的替本篇文章提供技術修正，不代表他們或他們的公司同 意我在本篇文章的論點)。也很感謝J.W. Aldershoff 給予本篇文章建議與批評，以及為 本文所做的努力。 Disclaimer (不保證) This article is meant to be a list of technical arguments showing some of the advantages of the + format over the - format, and it reflects only my personal opinion, and not the one of CD Freaks. It is not a detailed comparison of the two formats, and it does not take into account specificities of drives, media or third party software : only the format differences are compared here, as described in the DVD-R 2.0, DVD-RW 1.1, DVD+R 1.1 and DVD+RW 1.1 standards. Corrections are welcome by email, but questions and contradictory opinions should be posted to our forum, so that everyone can benefit from an open discussion. 本文意旨在於列出+R與-R技術爭論與優勢，這只是我個人的觀點，不代表CD Freaks。這 不是一個詳盡的比較，也未比較裝置，媒體或第三方軟體；僅就兩種格式的差異，於 DVD-R 2.0，DVD-RW 1.1，DVD+R 1.1 與DVD+RW 1.1 等標準之下做比較。歡迎將來信告知 錯誤，而問題與看法則請於論壇上發表，讓每一個人都能在開放的論壇獲得利益。 Michael Spath - [email protected] 譯者註：感謝前輩Michael Spath先生所提供給世人的資訊，本文權利於Michael Spath先 生所有。本文章不代表本人立場，本人亦不保證原文之正確性，與翻譯正確性。引用本翻 譯務必註明譯者。 -------------------------------- 有錯或建議請置於推文修正就好 因為我懶的管了 (逃走) --

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