補充一下，關於DVD 1X時的轉速比較準確的值，後來我在網路上查到的是內圈從1475 RPM 到外圈575 RPM ，而推論到其他倍數的轉速，則是幾乎是等比計算：
This results in a variable number of revolutions per minute (RPM) as disc writing/reading progresses from one end to the other. Recording begins at the inner radius and ends at the outer. At "1x" speeds, rotation of the disc varies from 1,475 to 575 RPM on 4.7GB media, depending on the record/playback head’s position over the surface.

而我前面所說的RPM值只是大概的經由NERO CD SPEED圖表去看的，應該有些誤差，如有錯誤請海涵。