Re: Checking the integrity of the Debian DVD

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

> But after writing them on the DVD using K3b, Brasero, or GnomeBaker,
> when I checked the integrity of the DVD using SHA256SUM they failed

This seems to be a neighbor of Bug#420716.
The advise given by Anne Bezemer should apply here too :

  head --bytes="`isosize /dev/cdrom`" /dev/cdrom | sha256sum


I would be interested in seeing the output of
  dvd+rw-mediainfo /dev/...
or
  cdrskin dev=/dev/... -minfo
with the affected media insterted into /dev/...
For comparison i'd like to know the exact ISO image size too,
(There are so many.)


I made a few tests about DVD track size alignment two days ago.
Burn results differ depending on the burn program, its options,
the media type and the media state.
All DVD use 32 KiB write chunks, but the readable size may
be of 2 KiB granularity. ISO images have 2 KiB alignment. So
that would allow exact size recording - in principle.

Candidates for exact size are DVD-R[W], DVD+R, BD-R.
I tested sequential blank DVD-RW, which are much like DVD-R :

- growisofs and wodim write exact track sizes if they use write mode
  DAO. With growisofs
    growisofs -dvd-compat -use-the-force-luke=dao -Z /dev/sr2=my_image.iso
  With wodim
    wodim -v dev=/dev/sr2 -dao -eject padsize=0 my_image.iso

- My own libburn insists in padding to full 32 KiB, even with DAO.
  It's in its genes. I will have to work on this. 
  growisofs writes full 32 KiB by default if not forced to DAO.
  wodim does nothing else but DAO, afaik.

I did not test growisofs and wodim with DVD+R or BD-R. (Costs me money.)
Thus my curiosity about other people's results.

DVD-RAM, DVD+RW, formatted DVD-RW, and BD-RE have no recorded size
but only a formatted size. This is normally substantially more than
the really usable data payload.


Have a nice day :)

Thomas