沒記錯的話
全世界DVD+/-R的銷售量是差不多的.....

此外，MKM、Ricoh染料大廠是屬DVD+RW Alliance陣營
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一直不用DVD-R當主力是DVD-R的ECC比DVD+R差....

有興趣看很多人轉過的這篇
http://www.cdfreaks.com/article/113

裡面有提到
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.

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.

轉貼的第二段裡面提到DVD-R1個ECC Block裡面有48bits是完全沒有在ECC的保護之下的
此外，在有24bits只有parity保護(A parity)，最後還有56bits只有parity保護(B parity)
意思就是DVD-R的一個ECC Block裡面有48bits完全沒有ECC保護，有80bits(24+556)則是用Partity的保護措施
剩下的才有完全ECC保護.....

Partity是什麼保護措施小弟不是很清楚，有查到的是這個
http://www.iazone.net/article.php3?...03724&mode=flat