Dual layer Data DVD

[Jerzy Zbyslaw]

As far as I’m aware the layers have never been separately addressable ever, and basically as the DVD-DL is 8.5 GB in size then anything written to it is presumably written to the first layer if < 4.7 GB in size and any overflow is written to the second layer up to its maximum size of 3.8 GB. Its like a hard drive which may have 100,000 tracks and you don’t know what track your data is on as the HDD firmware works it out.

Having said that you could use last century’s technology and write two separate sessions by writing a 4.7 GB session and then a 3.8 GB session as back in the 90’s that is what we used to do to incrementally write data to expensive CD’s and DVD’s at that time. Some multi session Audio CD’s probably still do exist today whereby a music CD is recorded as the first session which is all a CD player ever gets to see and so it plays without problems and the second session might have the bands low-res music video clip and the reason this works is that the PC defaults to the last session. Sony ran into some problems with this when they deployed anti-CD music ripping device drivers which could be used as a rootkit by hackers on some of their music CD’s with dire results. I recommend you don’t do multi-session disks as most people aren’t aware this is possible and are likely to get confused and probably wouldn’t be able to change the session in a PC even if aware the disk is multi-session. I never expect an optical disk to be multi-session and never check for this anyway and would most likely get highly irritated if someone deployed such a disk for me to use these days.

I’m somewhat confused by your original question and even more by your possible reasoning behind it but given optical media is so cheap then your better off burning two separate DVD’s and I’d advise you to give multi-session DVD-DL’s a miss. If there is some other reason behind your request obviously not apparent to me so far then kindly elaborate further and perhaps I can give you another opinion.

[Steve Kownacki]

Thanks, Jerzy. Agree with all you’ve said. Ah, the days of $12 blank DVDs…

Friend has a client with 4.5GB of data, and when the antipiracy is written for the content, it takes it about 200MB over the 4.7GB limit and it seems to be hosing up on the layer break with data for some reason. He can write blocks to fill the first layer as you suggested, with no luck with the copy protection. So being able to move “some” data to the 2nd layer without spanning it would be great.

I then inquired about what file types were being copied and it turns out to be a bunch of CAD stuff with associated HUGE JPG files. I suggested they compress they graphics files and you could easily save the file space needed. It worked.

Thanks for teaching me some new stuff about optical media.

Steve