Re: URGENT: VOBU length & number of sectors disagree

Hi Alan,

This error is almost exclusively returned on Images submitted on DVD-R, and is Eclipse's (Image verification software your replicator is using) way of saying that it couldn't read the Image data on one or more sections of disc. It is rarely (does happen though) an authoring system problem. I've only seen an authoring system output this error to hard drive/DLT a few times in 6 years. In fact, several times a month I get discs sent to me with this error at the plant and I find the Images are perfect - all were submitted on DVD-R.

Of course, I've found in most of these cases the replicator repeatedly told the author it was a problem with their image. In the cases they didn't tell the author it was their Image - they didn't say anything. But at least your replicator didn't go ahead and replicate - which happens all the time, too. I just finished troubleshooting a replication job where the discs were having problems playing back and even navigating - 10 discs (Hollywood A titles redone for European release), and they all had the dreaded "VOBU length & number of sectors disagree" errors on them - plus some other errors I thought I'd never live to see on a replicated DVD!

So, it's at least good your replicator has alerted you.

Here's the explanation of the error, as provided by the Eclipse ImageAnalysis program that your replicator used to test your DVD:

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"The calculated length of the VOBU and the length specified in the DSI field disagree.

The length of the VOBU is calculated using the address of the Navigational Pack and the length as specified in the DSI field (NV_PCK + VOBU_EA = LENGTH). During the analysis, the EclipseSuite tools read from the beginning of the VOBU until they reach the next NV_PCK, which indicates the end of the current VOBU and the beginning of the next. The EclipseSuite tools keep count of the number of sectors that make up the VOBU. If the number of sectors does not equal to the length specified in the VOBU_EA field then this error occurs.

In most cases, this problem has caused playability problems. It is for this reason that it is considered an error."
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Which means, a very high percentage of the time...if the replicators' optical drive drops a few sectors during the read of your DVD-R, they'll get the error, even if the Image is fine. Remember, even if a DVD-R is written perfectly on the best media, other optical drives out there can and will have problems reading it, at times (source: experience, and the NIST DVD Compatibility studies results - part of their results found on page two of my "Why Verify the DVD" article) - just one reason why DVD-R is not a suitable carrier for DVD Images to be used in mastering.

The only defense is submitting on DLT (I wouldn't use DLT 4000 drives, I've seen this same error twice over the years on tapes output by this super slow, old DLT drive) or hard drive or go with FTP; keeping the DVD production process off of optical media all the way to the very end, when it finally becomes a stamped DVD-Video DVD-ROM.

Though, Lucas couldn't bring himself to recommend that you resubmit on hard drive this next time, in his many replies (he works at a replication plant, after all :-), I'd say for sure do it, and make that your practice from now on (Please just send them DDP 2.0, nothing else); you've got to get the DVD-Recordable variable out of the equation to find out what is really going on.

Resubmitting on hard drive will either fix the issue, or determine that there is, indeed, a problem with your image. Then, it would be good to get someone to look at your Image - not too hard to fix, just got to find out where in the project the error occurs (you didn't give Eclipse's reported sector number location of the error), and see what the heck you and/or DVD SP might have done. :-)

Of course, I should say, before I would ever dream of submitting my authoring studio clients' Images to the replicator, an Eclipse ImageAnalysis test (through Eclipse ImageCopy) and other tests, are performed; That way, there's never a holdup or other surprises at the plant. But that's just me?

Good luck and take care,

Trai

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Trai Forrester
TFDVD Research Labs
DVDVerification.com