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Need VERIFY option based on LBA in boot sector


BitBasher
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If I verify a disc against an image/ISO file - life is good.

 

But, let's say I burn a disc from an ISO file in which I have an MD5 signature (like any linux distro). On the first burn, I can verify against the ISO image, and the MD5 will match the one I have for the distro image.

 

Now, let's say later I want to make another copy of the linux distro using an already burned disc (I no longer have the original ISO).

 

The problem is (it seems) that many disc writers pad a few extra sectors on the end of the media (perhaps to round the total sector count to be a multiple of 16).

 

So, if I read the disc image, I'm going to get a DIFFERENT MD5 value from what I expect because there are a few extra sectors now that are read back from the burned disc.

 

It would be REALLY HANDY if there was a new option in the VERIFY tab, something like:

 

Verify using LBA recorded in disc boot sector.

 

Since the actual number of sectors (LBA) of the original image are recorded in sector 16, this value could be used as an option when the media itself reports a greater number of sectors (padding). This would mean a VERIFY operation on a burned disc SHOULD return the exact same MD5 value as the original ISO - assuming the disc is 100% reliable.

 

Perhaps for the more advanced user, the VERIFY tab could have an option to specify what START and END sectors to be used for the MD5 calculation.

 

Thanks,

Bit.

Edited by BitBasher
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This only happens when you burn to DVD+ format discs - yes they pad to the nearest ECC block (16 sectors).

 

ImgBurn shows you the MD5 + Padded MD5 when that happens (assuming the source image sector total wasn't a multiple of 16) so just make a note of it.

 

It's too unreliable to take a value from the file system and use that as the size (I already attempt it when reading from DVD+RW/DVD-RAM/BD-RE). Remember the world doesn't revolve around ISO9660!

 

Maybe you can use something like IsoBuster to just read a certain range back to a file, it's not something I'll ever add to Verfiy mode.

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This only happens when you burn to DVD+ format discs - yes they pad to the nearest ECC block (16 sectors).

Hmmm, I have this happen when I burn (using ImgBurn) to a TDK DVD-R disc using a LiteOn SOHW-1693S drive. I also get this when I burn on my other LiteOn drive, but I don't have that model number.

 

If you want, I can send you more information on the drive and/or media from the ImgBurn logs.

 

 

ImgBurn shows you the MD5 + Padded MD5 when that happens (assuming the source image sector total wasn't a multiple of 16) so just make a note of it.

I don't see two MD5 values on a verify (just the one), probably because I have a padded DVD-R disc and ImgBurn doesn't do this step with DVD-R.

 

 

Maybe you can use something like IsoBuster to just read a certain range back to a file, it's not something I'll ever add to Verfiy mode.

I have a workaround now, but it involves reading the disc to an ISO file, then truncating it's length (using HxD), then calculating the MD5. Takes time, but it works. I was hoping for a faster solution.

 

Bit.

Edited by BitBasher
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If you're just burning an image in write mode, the padding only happens on DVD+, I've never seen it happen on DVD-. (again this is done by the drive itself)

 

If you use build mode, it'll pad to 16 because it's the only reliable method. (this is done by the program)

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