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I used the Nero CD-DVD Speed program to scan the burn quality of a 4.7 GB DVD+R disc. It reported significant errors (PIF errors) at the 2.5 GB mark of the disc. On the underside of the disc, I see a small scratch about 13mm from the outer edge of the disc. Would that correspond to the 2.5 GB mark of the disc?
pacoverflow
Posted 2015-12-19T20:46:23.290
Reputation: 1 155
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This could have some general usefulness, so I'll post a way to calculate approximate location on a DVD.
So a full standard disk is storing 4.7 GB on 8,759 mm2 of media surface, or 1,864 mm2 of surface per GB.
Say you're interested in where the 2.5 GB boundary is. That will require the inner 4,659 mm2 of media surface (2.5 x 1,864), which surrounds a 24 mm radius "hole" (1,810 mm2). So the boundary will be a circle with an area of 4,659 + 1,810 mm2, or 6,469 mm2. That circle has a radius of 45.4 mm.
Measuring a cheap DVD of mine, the actual diameter was 119 mm rather than 120, or a radius of 59.5 mm. So give or take the actual dimensions and rounding error, the 2.5 GB boundary would be 14 to 15 mm from the outer edge.
fixer1234
Posted 2015-12-19T20:46:23.290
Reputation: 24 254
Thank you. Just for reference, it looks like Nero CD-DVD Speed considers the max size of a DVD to be 4.5 GB (I guess it's counting by MB). The test burn that it did was 4310 MB in total, and I measured that to have a radius of 57mm. The data seems to start at a radius of 23mm. Also, to be precise, the errors occurred at the 2.57 GB mark. So plugging in those numbers, I got a radius of 46.38mm to the 2.57 GB mark, and that is exactly where the scratch is! – pacoverflow – 2015-12-21T07:35:32.760
I can't answer the question really, but a) be aware that all CDs/DVDs are written from the inside outwards, and b) because of constant rotation speed, the amount written in one 'lane' is constant, so if you divide the distance from the inner writable edge to the outer writable edge, the distances are proportional to the disc space (so half way out is half the capacity, 1/3 out is 1/3 the capacity, etc). Hope that helps. – Aganju – 2015-12-19T22:09:28.117
1actually, the data-rate is constant, hence the speed differential, so the distances are approximately out-referenced by a factor of 3, i.e. Pi*r squared, so hallway out is about ⅓ of the data. It still might as well be guesswork - if it's erroring, throw it away & use one that isn't. – Tetsujin – 2015-12-19T22:13:10.600