The DVD DL in detail
Both tables show the DVD DL characteristics and their competitors in pressed or DVD+R format. The DVD aspect has been developed with the intention of keeping the compatibility and the similarity with in one hand the DVD DL and the pressed DVD9 and in the other hand the regular single layer DVD. The data burning process is the same with the DVD+R DL as with the DVD+R and the +RW, they all use the lossless linking to keep no gaps between data. The track pitch is identical and has a 0.74 µm length. The track pitch is the distance between pits lines, measured from the centre of one line to the centre of the next line.
The wobble period is however raised of an additional 10% due to a more important channel bit length. In nanometre, the wobble period is the maximum amplitude of the pre-groove signal. The wobble period size change with the burner and the allowed burning method, because it determines the servo progression. The channel bit length represents the data density on the media. It is raised up to 0.146 µm on the DVD DL in order to improve the reading capacity and avoid interferences between the layer 0 and the layer 1.
The sensitivity is below the level of the classic 4.7 GB DVD+R. The classic DVD+R has a 4.5X density compared to the CD-R. The DVD DL only has a 4.X density compared to the CD-R. The whole capacity is connected to the density and fall from 4.7 to 4.27 GB by layer with a total of 8.55 GB for the DVD DL.
We also noticed that 30 mw of electrical power are required for the DVD DL compared to 19 mw for standard DVD. The gap is most likely due to the power loss due to the spacing layer and the first layer to cross. The burning speed for a DVD+R DL is currently 2.4 X.
When looking at the information of a blank DVD DL, we notice an 8.55 GB capacity and a DVD+R DL Book Type. The maximum burning speed is 2.4x or 3324 kb/s. The layer number is also indicated. However we also noticed that the DL media uses an OTP (Opposite track Path). So the burner starts in one direction on the first layer and continues in another direction on the second layer. In practice, the burner starts from the centre of the disc and goes to the circumference. And then immediately starts burning from the circumference of the second layer without coming back uselessly to the centre.
