Originally posted by RealMulder
I've wondered anyway why they always write "4,7 GB/120 min" on the DVD recordables. "120 min" means to me that a movie of 120 min length can fit on this medium. So how can it happen that 90% of the movies of the two-hours-class will NOT fit on 4,7 GB (or correctly speaking 4,36 GB)? How do the manufaturers calculate these 120 min?
To expand on what EpyxZ said, you can fit more than 120 minutes onto a DVD-R if you change the recording time. There are 4 different times aside from SP. They are FINE, SP, LP, and EP.
FINE = High Quality Picture Mode = 60 minutes
SP = Standard Mode = 120 minutes
LP = 2X Mode = 240 minutes
EP = 3X Mode = 360 minutes
In addition, you have two recording modes: VR mode and Video mode. The differences are that (1) Video mode is meant to play back on a standard DVD player while VR mode is playable back on the recorder and (2) EP recording time is not possible in Video mode.
Think about your standard VHS tape - you can record between 2 - 6 hours on most tapes depending on your recording time settings.
As for the difference between 4.7 GB and 4.36 GB: This is the same situation with hard drives. Manufacturers of hard drives and DVD media refers to a GB (gigabyte) as 1,000 MB. For computers, a GB is actually 1,024 MB, since computers use binary math and 1 GB = 2 ^ 10 MB = 1,024 MB = 1,073,741,824 bytes.
Take 4.7 GB as quoted by the media manufacturer and do this:
4,700,000,000 / 1,073,741,824 = 4.377 GB
Keep in mind this is raw data capacity... take lead ins, lead outs, and other overhead when storing data and you can effectively store about 4.36 GB of data on the disc.