You can 'see' the burnt part of a DVD

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tom hardwick
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You can 'see' the burnt part of a DVD

Post by tom hardwick » Tue Apr 28, 2009 8:35 am

Here's an oddity. You know that you can 'see' the burnt track on a DVD - it doesn't reflect the light so evenly.

I have a 40 minute film burnt at 6.5 mbps to a 16x Verbatim DVD-R. Flipping it over I can see that about half the disc has been used up.

I then copied this DVD onto exactly the same Verbatim blanks using Nero, using 'max' as the copy speed. When I flip these copies over, the entire surface of the blank has been 'used up'. Can anyone explain what's going on here?

Not that it worries me as the copies are identical to the original of course.

tom.

Michael Slowe
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Re: You can 'see' the burnt part of a DVD

Post by Michael Slowe » Sun May 03, 2009 9:27 am

Tom, it could be that 'Nero' has cleverly compared the data to be transferred with the capacity of the disc and used a bit rate that fills the disc thereby maximising the quality? Nice thought but probably unlikely!

By the way, you always maintain that transferring digital video never loses quality by going through generations. I have spoken to a number of professionals in the 'post' world who say that in theory this may be so but they don't find that this holds good in practice. I quote your mantra that it's only zero's and one's and they smile at me. Why do I always get in trouble by quoting my good friend Tom?

tom hardwick
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Re: You can 'see' the burnt part of a DVD

Post by tom hardwick » Sun May 03, 2009 10:23 am

When you transfer digital video (copying files from a Compact flash card to your pc, making a copy of a DVD, transferring a MiniDV tape to another tape and so on) you rely on the new medium (HDD, DVD-R blank, MiniDV tape) being in perfect condition. If it's not, then electronic error correction will usually reform the lost digits so that visually and aurally there's no perceived losses.

But we don't do these digital transfers in vacuum sealed, clean-air laboratories. We do them at home with recycled tapes, finger-printed DVD blanks and cables that we've plugged and unplugged very many times. So yes, there's always the danger that information will be lost on any digital transfer - but thank goodness it's nothing like the generational losses of the analogue age.

tom.

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billyfromConsett
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Re: You can 'see' the burnt part of a DVD

Post by billyfromConsett » Mon May 04, 2009 12:16 pm

I can't fathom that situation. I've noticed that if I put a 5 minute movie on a 4.5gb disk, it seems to use up half the disk, which is weird. There mustn't be an exact process into how much space is used up during burning. If you use a re-writable disk I wonder if it stores data in a different way to the once-only jobs we use mostly.

An aside, and apologies, but can I ask Tom: If I've a DVD with a bunch of movies on, and I want to copy just one of those films only, is that possible by extracting 0's and 1's? The only way I've found to copy a single movie is by playing the disk through a player and capturing the part I want. People have mentioned about copying the Vob files and re-naming them, but I can't that to work.

tom hardwick
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Re: You can 'see' the burnt part of a DVD

Post by tom hardwick » Mon May 04, 2009 12:33 pm

Billy - have a read of this thread:

http://forums.dvdoctor.net/showthread.p ... +vob+files

Alternatively NLE programs such as Edius allow you to play the DVD and put it in its entirety onto your timeline. From there it can of course be reedited any way you want to.

tom.

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Mike Shaw
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Re: You can 'see' the burnt part of a DVD

Post by Mike Shaw » Tue May 05, 2009 9:05 am

I've seen this anomoly of the 'burned dvd area' - burn a one minute movie to DVD and it takes up (it seems) as much burned area as a ten minute movie. Someone told me - or I read somewhere - a reason for this, and Im danged if I can remember - but it works out that even if you burn just a few seconds to a DVD a large(r) area gets 'burned out'. Nero is probably one of the 'worst' offenders for doing this: the burn software built into my editing program doesn't seem to be as bad. But the buirned artea doesn't seem to relate to film length.

Very odd.

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stingman
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Re: You can 'see' the burnt part of a DVD

Post by stingman » Fri May 08, 2009 3:29 pm

As to Quality loss that was mentioned......

We are led to believe that with digital we don`t lose quality. I think this! But let`s look at this the following way!

You burn a film onto DVD. You make a copy and if there are any problems, error correction takes care of it and the new copy has this new version of the film, including the bit that was error corrected. Now make another copy and say it needed to use error correction on this then surely this new copy won`t have the exact same data on it as your Master DVD!
Now would this show up as blocks on the screen or something else?

I hope you see my point. It`s certainly better then doing a copy in the VHS days, but DVD`s ARE NOT cracked out to be as we may have thought!

As for the adverts when CD`s came out like on `Tomorrows World` caking it up with cereals and stuff and bunging it into a cd player and having it still work! That was a bit daft! If you block out the sun it will get dark! The same will happen with a laser!

Have Fun Peeps and Smile ;-)
Ian Gardner
Film Maker

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