Looks like you've asked the same question EVERYWHERE
Please take a look at the StarBurn.h, everything is there. Here's some quote from it:
//
// 1X DVD speed constant (DVD-R, DVD-RW and DVD-RAM)
//
#define DVD_SPEED_IN_KBPS_1X 1385
//
// 2X DVD speed constant (DVD-R, DVD-RW and DVD-RAM)
//
#define DVD_SPEED_IN_KBPS_2X 2770
//
// 2.4X DVD speed constant (DVD+R, DVD+R DL and DVD+RW)
//
#define DVD_SPEED_IN_KBPS_2DOT4X 3324
//
// 3X DVD speed constant (DVD-RAM)
//
#define DVD_SPEED_IN_KBPS_3X 4155
//
// 4X DVD speed constant (DVD-R, DVD-R DL, DVD-RW, DVD+R, DVD+R DL, DVD+RW and DVD-RAM)
//
#define DVD_SPEED_IN_KBPS_4X 5540
//
// 5X DVD speed constant (DVD-RAM)
//
#define DVD_SPEED_IN_KBPS_5X 6925
//
// 6X DVD speed constant (DVD-RW)
//
#define DVD_SPEED_IN_KBPS_6X 8310
//
// 8X DVD speed constant (DVD-R, DVD-R DL, DVD+R, DVD+R DL and DVD+RW)
//
#define DVD_SPEED_IN_KBPS_8X 11080
//
// 12X DVD speed constant (DVD-R, DVD+R)
//
#define DVD_SPEED_IN_KBPS_12X 16620
//
// 16X DVD speed constant (DVD+R and DVD-R)
//
#define DVD_SPEED_IN_KBPS_16X 22160
//
// 18X DVD speed constant (DVD+R and DVD-R)
//
#define DVD_SPEED_IN_KBPS_18X 24930
//
// 20X DVD speed constant (DVD+R and DVD-R)
//
#define DVD_SPEED_IN_KBPS_20X 27700
//
// Other DVD speeds are just multiplier of ( DVD_SPEED_IN_KBPS_1X * N ) where N is drive speed
//