The SOHW-832S is the first (and so much expected) Dual Layer DVD burner in our possession. Until now, it was only possible to burn up to 4.7 GB DVD. It represents approximately a 2 hour MPEG2 video like a movie from a DVD. With this format it is not possible to burn a dual layer DVD9. And it is also impossible to reach over the 4.7 GB of data, which is rather small for movies.
The DVD+R format is the first which benefit from this technology. Blank DVDs manufactured by Verbatim are still rare and are expensive This price is quite high compared to the price of a 4.7 GB DVD+R from the same brand. However prices should fall once the DL burners will grow in numbers and become more popular.
The process, named 2P process, is similar to the recording of a pressed DVD9. The blank DL DVD has two thin organic layers separated by a transparent spacing layer. When heated by the laser, each layer is irrevocably modified. The process is similar to classic DVDs. However the burner and the DVD player have to be able to differentiate the layer 1 from the layer 2. So, the capacity to transmit light to the layer 1 is raised up of 50% to allow the signal to pass once in one way for the burning and as much as desired in the other way for playing.
However, the first layer reflectivity has to remain of 18% at last for the DL compatibility. The second layer (the lowest on the DVD) has a stronger reflectivity and a highest sensitivity to the laser. The first layer absorbs and reflects a share of emitted light. The spacing layer is approximately 55 microns wide. The laser beam points to one or the other layer by modifying the lens position.
