Mouse wrote:
I do agree that
current DVD players are still able to read the data
from any original DVD media burned when they first became available.
Were the first DVDs burned? I've always assumed they were pressed,
more or less like CDs. Am I wrong?
Burned or pressed, the DVD drive seems to read the DVD
equally well.
What about the physical properties of the media? I tend to
assume that the media of a CD is different from the media
for a CD. Does anyone have the physical specifications?
Since a DVD drive can read both a CD and a DVD (as well
as, for many drives, but not all) burn both a CD and a DVD,
the media can't be that different. However, since my DVD
drive is able to distinguish between a DVD blank and a CD
blank, I assume that the media must be somewhat different.
The file structure is probably the most important aspect. Do
a DVD and a CD have essentially the same file structure? Since
the DVD typically holds ten times the storage capacity as a CD,
a 32 bit file structure would seem just about correct for the file
structure for both the CD and the DVD.
At one point, I burned a CD with both a CD file structure starting
at CD sector 16 and an RT-11 file structure starting at CD sector
zero. Where the RT-11 partitions started (every 16384 sectors
of 2048 bytes or 65536 blocks of 512 bytes), I placed spacer
files with originally all zeros and filled in the RT-11 file structures
after the CD was burned with the CD file structure and converted
to an ISO image on the hard drive. It took a couple of attempts
to figure out everything, but after converting the first CD image to
an ISO file, I used RT-11 to locate all the files from the CD. The
first RT-11 file became the file structure of the CD.
As for all types of storage, the CD and now the DVD, seems to be
about the most stable and unchanging of all storage types. However,
I understand that many current PCs these days no longer have DVD
drives. Is that the trend?
Jerome Fine
