Does anyone know?

Can anyone explain to me why this happens…two different instances in the last month… We (my family) had our old 8mm movies transfered to DVD - and had the company make three copies. When I got the copies home, one DVD played in both my PC and my DVD player; one copy played on the PC but not the DVD player, and the third copy played on the DVD player and not the PC. Of course I called the place and they had me bring them back to check them. When they tried them, the one that didn't play on my PC played in their PC and in their DVD player, the other copy did the same thing that it did at my house - In the end, they gave me two more copies, both of which played in both my units. That was the first instance. This past weekend, my daughter got a CD copy of their vacation pictures made at the local drug store. They played on her PC but not on either of their DVD players, even though both players state that they play four different types of DVD's & CD formats. She thought it might have been a bad CD so she made a copy of it, but the copy didn't work in their DVD players either. So she thought maybe it was because it was a CD disk and not a DVD disk. She asked me if I would make a copy on a DVD-R disk. So I did and played it back on my PC. Both her CD disk and the DVD disk that I made played on my PC; however, on my DVD player, HER original copy played in my DVD player, but the one that I made didn't - and I have played DVD's from the same pack of DVD-R's in my DVD player, so I know it doesn't have anything to do with the disks being + or -. Can anyone explain why this happens?

There are lots of variations in the "home built" CDs or DVDs that are not usually present in the proprietary article. The organic dyes used in the home variety (that carry the "peaks and troughs "etched" by the laser) are sometimes unreadable in a "stand alone" DVD player.

A proprietary DVD pressed from a master as part of a long run is of a uniform consistency and does not rely on a surface dye to "encode" the data.
The power and performance of the lasers used in the home and professional areas are also significantly different. not to mention individual disc differences from machine to machine and between the manufacturers various products.

The whole area of performance criteria is reasonably well documented by both the main manufacturers and also by academic research but it can and has been summed up as:

there are differences between home burnt and major production runs…….some work and some dont!

Regards
paws