Originally posted by jsl
That they're are specified is almost certain but what they are is another question (I don't have the specs so I don't know but it would be odd to change them so they're most likely the same as for SL DVD+R/RW.)
For starters, wouldn't it be necessary to define the specific transparency characteristics for the bottom layer, the reflectivity of the top layer and signal strengths achievable from the second layer? For that matter, it'd also seem necessary to redefine the read characteristics of the bottom layer since they will certainly be affected by the semi-transparent reflector and the mixing signals coming from layer 2 (critical focus won't eliminate them entirely). Seems most of these issues would not have been covered by the existing single-layer specs.
As a person who has worked a fair amount with slightly similar complex technologies, my bet is that dual-layer will be an engineer's (and physicist's) nightmare for some time to come. Personally, I don't think I wish to be an early buyer into these new dual-layer burners. Not only will competing specs (+ and -) complicate things, they're pushing the limits of existing technology. Those things seldom come easy. Dual-layer may be interesting at the current time, but much better technologies aren't too far down the road. It remains to be seen whether dual-layer will really become reliable and commonly available before higher-density discs are marketed.