Question about DVD reading and decoding

Hello all.

I don’t mean to be critical of the DVDFab software, but can somebody explain something to me?

Why is it that when DVD publishers publish a new DVD with a slightly different copy protection scheme, existing DVD players don’t need to be updated to decode and play them, but backup software such as the DVDFab series does need to be updated to decode and copy them?

Is the way DVDFab reads and decodes DVDs fundamentally different from the way DVD players do it? And if so, then why is it different?

For example, an older version of DVDFab Decrypter could copy “Pictures of Hope”, an infomercial DVD about an antidepressent drug called Effexor XR and create a playable DVD, but it was full of duplication glitches. But a newer version, DVDFab Platinum v 3.0.7.2 produces a glitch-free copy.

DVDFab Platinum v 3.0.7.2 can’t make a glitchless copy of Spike Lee’s :“When the Levees Broke: A Requiem in Four Acts”: Disc 1. The result has multiple duplication glitches at the 38 minute and 59 minute points. But I imagine that a newer version will.

From what I’ve read in the release notes and other threads on this forum, this pattern of required updates has repeated many times.

So, to repeat my original question, is the way DVDFab reads and decodes DVDs fundamentally different from the way DVD players do it? And if so, why?

DocuPerson.

All excellent questions I have wondered about myself, only a few of which I feel qualified to answer, but here goes…

Like everything else, DVD copy protection schemes have changed over time. The original CSS type of protection was the same for every disc; a binary code could be extracted that made all the content copyable. The code was different for each disc, but the method for extracting and applying it identical. Hence no updates required. Newer schemes, generally referred to as “structure protection”, work differently and are different from title to title, each with different decoding requirements for a proper read. Hence updates required for many (particularly Sony) titles.

Is the way DVDFab reads and decodes DVDs fundamentally different from the way DVD players do it? And if so, then why is it different?
Yes it is. I have no idea why, nor why player type smarts could not be written into copying software. The idea that it can’t is counterintuitive, but I’m sure there’s a good reason.
For example, an older version of DVDFab Decrypter could copy “Pictures of Hope”, an infomercial DVD about an antidepressent drug called Effexor XR and create a playable DVD, but it was full of duplication glitches. But a newer version, DVDFab Platinum v 3.0.7.2 produces a glitch-free copy.
This sounds more like a read error or bad spot on the original disc. Error handling has improved as the product has evolved. Is the original a DVDR (bluish) or DVD-ROM (silver)?
DVDFab Platinum v 3.0.7.2 can’t make a glitchless copy of Spike Lee’s :“When the Levees Broke: A Requiem in Four Acts”: Disc 1. The result has multiple duplication glitches at the 38 minute and 59 minute points. But I imagine that a newer version will.
Again sounds like a read error. I would upgrade to 3.0.8.0 and see how you have error handling set up in Common Settings–>Read. Select the “Ask/Retry/…” button and allow a larger number of retries in the “Retries” pulldown menu. Brief hiccups in the output are not typical copy protection symptoms.

Hello Signals.

Newer schemes, generally referred to as “structure protection”, work differently and are different from title to title, each with different decoding requirements for a proper read.

Can you point me to some more information about “structure protection”?

I have no idea why, nor why player type smarts could not be written into copying software. The idea that it can’t is counterintuitive, but I’m sure there’s a good reason.

I’d like to learn what that is.

This sounds more like a read error or bad spot on the original disc. Error handling has improved as the product has evolved. Is the original a DVDR (bluish) or DVD-ROM (silver)?

Both discs are silver.

Again sounds like a read error.

I agree, but I don’t think the errors are because of dirt or scratches. I think that they encoded into the DVD master. They are intentional errors that are part of the copy protection scheme. I’m an old timer, and they used to do similar things to floppy disks when software was distributed on them.

I would upgrade to 3.0.8.0 and see how you have error handling set up in Common Settings–>Read. Select the “Ask/Retry/…” button and allow a larger number of retries in the “Retries” pulldown menu. Brief hiccups in the output are not typical copy protection symptoms.

That’s puzzling. When I backed up “When The Levees Broke…” it seemed to be doing a lot of retrying. I thought it was excessive. Judging from the program’s progress bar and the LED on the DVD drive, the program spent nearly all of the 1 hour and 20 minutes required to process the disc in only a couple of spots. But “Retry times” was set to “1”.

Something else is strange. "Ask retry/ignore/abort

Hello and welcome to the forum. If it toke you that long to complete the project, you might want to reset your DMA first off, or at least make sure it’s on.What kind of burner are you using and when was the last time you checked the firmware for it ? The Ask retry box pops up when the program comes across a problem and can’t decrypt or rectify and asks you what you want to do. Giveing you the option to let it work the problem out or include the errors. ~ Mike

DVD Publishers spend a lot to prevent copying, but they have to make sure they will play to keep returns down. They usually try to put it in the extras etc hoping if it will not play them, people will not return them. They licensed technology to all hardware makers to prevent copying. I am not sure how it works, but would guess there is a chip that runs a check sum before allowing the DVDs play. They tried to get MS to integrate a verification in Windows. The old Microvision on VHS tapes could be compromised by a chip why not a chip for DVDs. They have so many numbers to crunch that it is almost impossible to guess the right one. Dish Network use to build DVRs with MS programming built in, but no longer because they were too easy to hack and MS contract would not allow them to change their programing. Since the will not run with new cards. Cars use to have different cuts on a certain number of keys and it was common to find someone Else’s key that would start your car. Now they have one cut that fits all but has a RFID chip that is programed to your car, and if you loose all of them you have to pay out some big money. They plan to embed this in the new HD DVDs. They can be cracked but will have to have several computers and several hours time. It is not easy, I have been trying because I have only 1 key for my car. I have spent about $1000.00 to keep from paying the dealer a couple hundred for a key, but can also control other parts of the car. Do some google searches.

Mack

I agree about the RESETTING DMA

(Sorry, I accidently posted an incomplete message earlier. I couldn’t figure out how to delete it, and wasn’t able to edit it before the 30 minute limit expired. The following should be complete, but I probably won’t be able to read the responses until tomorrow.)

Hello Signals.

Newer schemes, generally referred to as “structure protection”, work differently and are different from title to title, each with different decoding requirements for a proper read.

Can you point me to some more information about “structure protection”?

I have no idea why, nor why player type smarts could not be written into copying software. The idea that it can’t is counterintuitive, but I’m sure there’s a good reason.

I’d like to learn what that is.

This sounds more like a read error or bad spot on the original disc. Error handling has improved as the product has evolved. Is the original a DVDR (bluish) or DVD-ROM (silver)?

Both discs are silver.

Again sounds like a read error.

I agree, but I don’t think the errors are there because of dirt or scratches. I think that they are encoded into the DVD master. They are intentional errors that are part of the copy protection scheme. I’m an old timer, and they used to do similar things to floppy disks when software was distributed on floppies.

I would upgrade to 3.0.8.0 and see how you have error handling set up in Common Settings–>Read. Select the “Ask/Retry/…” button and allow a larger number of retries in the “Retries” pulldown menu. Brief hiccups in the output are not typical copy protection symptoms.

That’s puzzling. When I backed up “When The Levees Broke…” it seemed to be doing a lot of retrying. I thought it was excessive. Judging from the program’s progress bar and the LED on the DVD drive, the program spent nearly all of the 1 hour and 20 minutes required to process the disc retrying in only a couple of spots. But “Retry times” was set to “1”.

Something else is strange. “Ask retry/ignore/abort when reading error” was checked, but the program never reported an error or asked me how to handle it, indicating that there were NO read errors. It doesn’t make sense.

Here is a bit of history.

I first encountered this problem while using DVDShrink. I think it reported a CRC or some other type of read error. The first time I had encountered this, the disc had problems on a regular player also. I fixed both problems by polishing the DVD using something called Kit Scratch Out, a car polish that I got from WalMart.

The second time it happened, polishing the DVD didn’t work. I concluded that the read error was put on the disc intentionally by the publisher as a copy protection method, the way software publishers began to do years ago on floppy disks, so DVDShrink needed to be updated to handle read errors.

I couldn’t find a DVDShrink update, but found something new called DVDFab that worked, sort of. Its output was playable, but had annoying glitches.

The glitches were what I call “duplication glitches”, because it appeared that they were the result of blocks of VOB file being included in the output twice. I could see split seconds of video repeated, with motion compression errors apparently because of the referencing of incorrect frames. And I could hear split seconds of audio repeated. I thought that what might be happening was that the publisher was duplicating VOB file blocks, once with a flaw that would cause a read error, and once without a flaw.

I further concluded that the players were probably simply throwing away any VOB file blocks with read errors and going on to the next block. But since they were throwing away blocks that were not needed, the disc played flawlessly.

But the copying software was apparently doing something different. It was including every block in the output stream, including the duplicate blocks that had read errors, resulting in the duplication glitches.

If this was true then a fix would be easy. I was going to try to contact the software author and suggest the fix: Discard blocks with read errors. I didn’t do that because the next version of the software seemed to work okay. I thought that the author had figured it out and made that fix.

But apparently that is not what happened, because new DVDs require new software updates. Based on all the data I’ve seen so far, this is what seems to be happening:

DVDFab will handle a DVD in one of 2 ways.

  1. It will keep VOB file blocks with read errors, which results in (duplication) glitches.

  2. It will discard VOB file blocks with read errors, which results in a flawless copy.

Old DVDs are copied with method 2. New DVDs are copied with method 1. But the meanings of “Old DVD” and “New DVD” are not constant. They depend on the version number of the software.

So my new questions are: Does my analysis seem reasonable? If it is then: Why is method 1 used at all?

DocuPerson

This is a fascinating topic to me but beyond the depth of my knowledge to give you definitive answers–I’m still looking for them myself!:slight_smile: I do think the copying algorithms involve more complex choices than 1 and 2 listed at the bottom of your post, though, and those choices would only provide the proper results on discs with no real read errors (as opposed to bad data purposely inserted in the mastering process). Here are some things you can read that provide some insight on the decrypting process: this one in particular is good (but a little hard to follow); this forum has lots of good topics as well, as do the CD Freaks forums, where we reside now. Check this thread every day or so, someone more knowledgeable may come along and enlighten us. And a belated welcome to the DVDFab forum.:slight_smile:

Hello signals.

I’ve been busy with other things, but I finally got around to checking your link suggestions.

This is a fascinating topic to me but beyond the depth of my knowledge to give you definitive answers–I’m still looking for them myself! I do think the copying algorithms involve more complex choices than 1 and 2 listed at the bottom of your post, though, and those choices would only provide the proper results on discs with no real read errors (as opposed to bad data purposely inserted in the mastering process). Here are some things you can read that provide some insight on the decrypting process: this one in particular is good (but a little hard to follow);

Yes, and it’s mostly procedure, not explanation. I think I’ve seen that guide and actually used FixVTS before.

this forum has lots of good topics as well,

doom9 I’ve also read. I think that I’ve learned more there than anywhere, but never an answer to this particular question.

as do the CD Freaks forums, where we reside now.

These are all fine as far as they go. But they’re all mostly “do this” or “try that”. There’s very little (that I could find) about what is actually going on in the copy process, and nothing about why players can read and decode DVDs without needing updates but copiers can’t.

Check this thread every day or so, someone more knowledgeable may come along and enlighten us. And a belated welcome to the DVDFab forum.

Thanks.

Viewing the source code might answer my question. I was a software engineer in an earlier life. I don’t suppose the source code is available for DVDFab? If not then I guess I’m out of luck for now.

Thanks again for all your help.

DocuPerson.

Welcome back and thanks for following up. Well, I never said it would be easy:) . You’ve looked everywhere I know to look and reached the same dead end. Trying to find answers like this that intuition tells you (probably incorrectly) should be obvious to somebody somewhere is especially frustrating. Although it violates the EULA, at least parts of Fab can be decompiled; a poster a few months ago did this to find a bug and posted the fix on the forum. And I am convinced there are people, particularly on doom9, that could answer this in a few sentences, even given that the question and its answer are more complex than they appear. PM me if you make any headway; I will do the same.:clap:

Special Chips that allow read but not copy are used to identify DVD but disallow copying. Ever heard of prime numbers, those that can continually be divided until a checksum appears. Same technique used in satellite TV decoders, simple example (22=44=16*16=256) sounds simple until it gets larger. John Hopkins University used several computers with special boards to break a code in a Ford car key, but it took running 24/7 for weeks to do it. Why not just copy number? Well they put some skip numbers in it also and if you had number it would only allow play. Player manufactures have to buy those chips which know how to decrypt the number for playing. Go Video developed a player that would copy VHS to VHS but kept the Macrovision on the copied tape. So the enyption has to be worked around, to record DVD without encryption. Know that boy that comes out and jumps toward the lake on some movies. That is a part of the encryption and when you try to shrink it it keeps doubling until file gets too big for any more files. This encryption is not simple.

Mack

Hello Mack.

Special Chips that allow read but not copy are used to identify DVD but disallow copying. Ever heard of prime numbers, those that can continually be divided until a checksum appears. Same technique used in satellite TV decoders, simple example (22=44=16*16=256) sounds simple until it gets larger. John Hopkins University used several computers with special boards to break a code in a Ford car key, but it took running 24/7 for weeks to do it. Why not just copy number? Well they put some skip numbers in it also and if you had number it would only allow play. Player manufactures have to buy those chips which know how to decrypt the number for playing.

Yes, I’m familiar with prime numbers and various encryption systems. But I didn’t think encryption applies here, because the problems seemed to be about a different copy protection method, specifically the use of intentional read errors. They can be used whether encryption is used or not. Another example is encoding a DVD so that it requires more space than can fit on a single layer DVD. Again, this can be done with or without encryption. Or am I mistaken about this?

DocuPerson.