(O/T) DVD deterioration

[John Stewart Miller]

I've heard reports that people have had problems with DVD-R discs over a year old. That the vision or play is marred.

Worried I studied my own. I only archived for around 9 months on DVD+RW. Studying these it seems some items look as though they may have become a bit 'swimmy' and grainy since original transfer. I'm concerned that the images may become destabilised over time, or whether this is impossible and that the defects may be due to the original source. I'm sure they looked better when I originally did them.

I wondered about the reliability of DVD formats and does anyone have any advice ?

[Nosmo King]

As DVD had only been around less than a decade then no-one really knows how long they will "generally" last. Ask again in 30 years!

And of course it will vary from disk to disk .. it won't be as simple as say every DVD+R will go tits up after 13 years 27 days and 2 hours or whatever ...

For archiving use "once only" formats .. -R or +R, re-writable formats are for just that - for re-use by their nature - not for permanent storage - and so will likely "fall apart" much quicker. Avoiding the absolute cheapest option may well be a good long term investment too.

Best things is for anything really valuable at least make back up copies or better still keep the original source if possible .. and keep the disks away from sunlight etc.

[Laurence Piper]

It seems to be a far more complex issue than that of videotape longevity though. Just by visiting A-V forums, it becomes clear that the reliablilty of recordable DVD is a hot issue (pre-recorded DVD not being affected in the same way, from what I can gather). Apparantly it's to do with the dyes used in the manufacture that chemically alter in time. Just buying quality brands and storing them well doesn't seem to be a guarantee of them lasting either. It's worrying. Certain older discs I have recorded myself over 18 months or so (which I don't consider long ago in archive terms!) seem to display worrying occasional defects to playback (random pixcellation, momentary freezing etc) that were not there originally. I now back EVERYTHING up to tape as well and if I record off-air, I also make a video recording. Crazy that I should have to do this but what else can you do? Making disc to disc backup copies is all fine but those backup discs can also fail in the same way.

Personally I now archive on DVD-RAM (which, according to all knowledgeable reports that i've seen, is far more reliable than the other formats as it's make-up is different) and use the other formats to make viewing dupes etc. The RAM discs I consider as a holding medium until such a time as a more ideal archiving format arrives to which I can transfer again but maintaining maximum quality. And anything I transfer from tape to disc, I also keep the video master just in case!

I'm not an expert on the subject but the above are basic facts that i've picked up from various sources. Is there anyone reading this who can provide more technical fact on the subject? I'd be interested to hear of others' experiences with DVD and any conclusions reached. Archiving becomes a nightmare if you can't rely on the medium you use to record to!

[john g]

It probably applies to every recording medium since the beginning of the twentieth century, that in years to come you will find pristine DVDs kept in diabolical conditions , then you might find others that have been looked after that are disintegrating. Such is nature.

The video laserdiscs of the 1970/80s can suffer with big flashy drop out , but they were recorded in analog and the dye coating was not sealed properly, so it could flake off. The advantage of analog though is the fact
no matter how bad things get , it will still show some sort of picture.

DVDs today usually have the delicate dye coating sealed in another wafer of plastic.
This should protect them from oxygen and of course greasy fingers for years.

The only thing you have to worry about is how the chemicals change under the plastic

[Peter Roberts]

I've not read up on DVD longevity, but if they had degraded a 'swimmy' and grainy effect is not what you'd expect.

Writing to DVD is more like writing a file to a floppy disc than recording to analogue video tape. A file on a floppy can either be read perfectly, or the operating system will give you an error message and refuse to read it at all.

For 'file' read 'section of the recording'. A failure will usually lead to skips, freezes or squares missing from the picture.

But it is not completely impossible that the effect you describe is due to disc degradation. With some CD players, one make of CDR will sound noticeably different from another. The best explanation I have heard of this is that with a poorly manufactured disc the reading mechanism has to do more work to keep the laser focused on the track, and this leads to electronic noise in the system which, due to imperfect design, effects the audio output.

In such cases there is no actual loss of information on the disc - it's just that certain players perform badly when reading such discs. If you suggest that a perfect digital copy can sound different from the original it can lead to howls of derision from people who think they know more than they do.

To test what's happening you could use a PC to make a copy of your DVD. If the PC can copy the contents to the hard disc without errors the disc has not degraded seriously enough to lead to data loss. Your original recording is now on the hard disc unmodified from the day it was written.

You can now write this to a new disc and compare how your DVD player handles playing the old and the new. Be careful though as the mind can be easily fooled. It would be best if you did a blind test, e.g. get someone else to flip a coin and put one of the discs in, and see over 10 trials if you can tell the difference.

[TR16]

i been archive my VHS tapes on to DVD for years now using a TBC and a MPEG2 Hardware encoder. my tips would be:
1: burn at the SLOWEST rate possible, the faster it is then the lighter the laser burns the tracks onto the DVD so the more chance of skipping during playback.
2: use DVD R- if possible
3: do a verify after each burn.
4: store the dvd in a dark place.
5: dont play them too often
i started to convert to SVCD/DVD in 2002 and since then ALL my CD's(SVCD) now have defects and about 10% of my DVDs have defects, luckly the DVD's could be salvaged by using recovery software but it was a pain in the arse. My next move is to wait until a 1Tera byte harddrive is available and make a backup of all my DVD collection onto it. I just hope they will last that long

[williamM]

I know that some computer cds have started to deteriorate after as little as 10 years and some of the laser disks from the UK "Doomsday project" of the early 80s are now unreadable.

I've found some things that may be of further help

www.dvdtown.com/messageboard/topic/2/19029/

seems to be a forum that seems to deal with this issue

also

www.smh.com.au/articles/2003/01/31/1043804519345.html

and

www.manifest-tech.com/media_dvd/dvd_compatibility.htm

[John Stewart Miller]

Peter said:

I've not read up on DVD longevity, but if they had degraded a 'swimmy' and grainy effect is not what you'd expect.

Writing to DVD is more like writing a file to a floppy disc than recording to analogue video tape. A file on a floppy can either be read perfectly, or the operating system will give you an error message and refuse to read it at all.

For 'file' read 'section of the recording'. A failure will usually lead to skips, freezes or squares missing from the picture.

But it is not completely impossible that the effect you describe is due to disc degradation. With some CD players, one make of CDR will sound noticeably different from another. The best explanation I have heard of this is that with a poorly manufactured disc the reading mechanism has to do more work to keep the laser focused on the track, and this leads to electronic noise in the system which, due to imperfect design, effects the audio output.

In such cases there is no actual loss of information on the disc - it's just that certain players perform badly when reading such discs. If you suggest that a perfect digital copy can sound different from the original it can lead to howls of derision from people who think they know more than they do.

To test what's happening you could use a PC to make a copy of your DVD. If the PC can copy the contents to the hard disc without errors the disc has not degraded seriously enough to lead to data loss. Your original recording is now on the hard disc unmodified from the day it was written.

You can now write this to a new disc and compare how your DVD player handles playing the old and the new. Be careful though as the mind can be easily fooled. It would be best if you did a blind test, e.g. get someone else to flip a coin and put one of the discs in, and see over 10 trials if you can tell the difference.

Thanks for this Peter. My alarm was actually triggered by reports coming my way from others stock (regarding +R and -R stock). For the first 9 months I was archiving (and editing) in +RW format, so the same issues may not apply. I reviewed some of my own to test the theory. I have since noticed that some discs contain dupes of items from cable recordings off air, with other items that looked clear (not 'swimmy'); from other sources.

My conclusion is that the quick study of my stock may have been fired by paranoia! Some of the cable items had to have tracking realigned (not recorded on the machine used for playback). The quality was grainy anyway, and 'dots' always seem to cause visual fluctuation when coverted to DVD. I think additionally the tracking may have caused some minor discrepancies in jitter compensation when transferred to DVD.

Luckily the original tapes these items originate from were largely kept as there were too many items I wanted to keep on them. The fact they were important recordings was why I wanted to transfer them in the first place!

I think the best policy might be to ensure; as one should with important old audios recordings; review tapes preiodically and make new copies to the best current format available.

I should also consider I suppose that DVD+R is reputed to be higher quality than -R so presumably should be more reliable?

Thanks also to everyone else who contributed useful, intelligent and interesting remarks to this debate.

[Laurence Piper]

john said:

It probably applies to every recording medium since the beginning of the twentieth century, that in years to come you will find pristine DVDs kept in diabolical conditions , then you might find others that have been looked after that are disintegrating. Such is nature.

The video laserdiscs of the 1970/80s can suffer with big flashy drop out , but they were recorded in analog and the dye coating was not sealed properly, so it could flake off. The advantage of analog though is the fact
no matter how bad things get , it will still show some sort of picture.

I think the problem is far more pronounced with DVDs though. For instance, we know VHS tapes (and Betamax for that matter) will play after 20 years - we don't have the same assurance with DVD, where discs are commonly failing after just a couple of years (let alone a decade or two). Sure, some discs will - by sod's law - play years later that have not been looked after whereas those that have will not. But by and large, the failure rate for discs seems WAY higher than with tape - and that's after just a few years! Someone needs to get their act together at the manufacture and formulation stage.

[SteveS]

john said:

It probably applies to every recording medium since the beginning of the twentieth century, that in years to come you will find pristine DVDs kept in diabolical conditions , then you might find others that have been looked after that are disintegrating. Such is nature.

The video laserdiscs of the 1970/80s can suffer with big flashy drop out , but they were recorded in analog and the dye coating was not sealed properly, so it could flake off. The advantage of analog though is the fact
no matter how bad things get , it will still show some sort of picture.

DVDs today usually have the delicate dye coating sealed in another wafer of plastic.
This should protect them from oxygen and of course greasy fingers for years.

The only thing you have to worry about is how the chemicals change under the plastic

The best format of course for longevity is film -- especailly mylar/estar based which is supposed to have a shelf life of 5000 years or something like that. Acetate film stock can develop vinegar syndrome, but it still outlasts most other formats. And to avoid colour fade, it's best to make B&W separations of the original negative. Next best is IB Dye transfer prints, followed by modern colour filmstock which has much more stable dye layers than early dye-coupler based filmstocks.

This of course is not something you can easily do at home.... But studios should be archiving things this way -- digital data storage is problematic - if your master deteriorates, or if the technology changes, it may be impossible to recover any of it...

[Peter Chadwick]

I've just lost my 54th audio cd-r. All have been 'name' brands, all have been well stored and looked after and all have lasted less than two years. It's the reason why I daren't buy a DVD recorder and trust my video collection to anything on a silver disc. Some of the stuff I've lost is irreplaceable, and I could kill when I lose another disc. The trouble is, no one can guess at how long discs will last.

[Laurence Piper]

This just reinforces my point about DVD being an unreliable medium. We're having a very useful and in depth discussion about this subject at the moment on The Mausoleum Club forum, Peter, if you'd like to join in? ("Off-topic waffle" section).

[Andrew Doherty]

I have said it before and I will say it again:

Don't get rid of the VCR and the tapes.

I have a computer DVD recorder and a DVD player. But I am under no illusions about such matters.

Yours,

[williamM]

the new generation of disc players will be coming out in over the next 2 or 3 years so perhaps these problems will have been eradicated(hopefully)

[John Stewart Miller]

john said:

It probably applies to every recording medium since the beginning of the twentieth century, that in years to come you will find pristine DVDs kept in diabolical conditions , then you might find others that have been looked after that are disintegrating. Such is nature.

The video laserdiscs of the 1970/80s can suffer with big flashy drop out , but they were recorded in analog and the dye coating was not sealed properly, so it could flake off. The advantage of analog though is the fact
no matter how bad things get , it will still show some sort of picture.

DVDs today usually have the delicate dye coating sealed in another wafer of plastic.
This should protect them from oxygen and of course greasy fingers for years.

The only thing you have to worry about is how the chemicals change under the plastic :D

So the technical point you make here John; to verify; is that the construction of the discs themselves; or processes involved are the key factors in discs longevity. This, rather than anything to do with factors of processes acting upon them such as finalising?