For example the 1X speed on CD which is 150KB/s, is based on the number of sectors read to play a one second CD audio track at normal speed. i.e. since CD audio is 44100Hz 16-bit stereo, this is 44100 x 2 x 2, or 176400 bytes. 176400 bytes is equal to 75 audio track sectors (sector mode 0; 2352 bytes per sector). So, it's 75 sectors per second. On data CD (sector mode 1, or mode 2 form 1), one sector is 2048 bytes. So, 75 sectors is 150KB. Thus, 150KB/s. That's when it become the 1X CD speed. But what about 1X DVD speed? There's no audio track on DVD (i.e. sector mode 0; 2352 bytes per sector). DVD has only one sector mode, which is mode 1 (2048 bytes per sector). According to OSTA, 1X speed is equal to 1.32M/s (http://www.osta.org/technology/dvdqa/dvdqa4.htm). But that's all. There's no explanation on how the 1.32MB came to be the 1X DVD speed. How it's decided that 1X DXD speed would be 1.32MB/s. Was is it on a whim? Maybe it's the fact that at that time, the DVD technology is capable of reading only up to 1.32MB/s, so they decided that it would be the standard for the 1X DVD speed?