[Pkg-libburnia-devel] Bug#918006: DVD-RAMs are always displayed as blank with , even with data written.

[Thomas Schmitt]

Hi,

it is not a bug but a feature. In the context of the cdrecord emulation
being "blank" means being writable without further precautions. The
media types DVD-RAM, DVD+RW, BD-RE, and formatted DVD-RW are overwritable
without the need for a blanking run.

If you run xorriso in its native mode:

  xorriso -outdev /dev/sr0 -toc

then you will probably see either

  Media status : is written , is appendable

or

  Media status : is written , is closed

depending on whether an ISO 9660 filesystem is recognized or not.

An overwritable medium will be considered to be blank only if it is unused,
or its first 64 KiB are all 0, or if it bears an ISO 9660 superblock which
was invalidated by xorriso command -blank.

The difference between both modes comes from the fact that xorrecord
does not care for the kind of content, whereas xorriso's native mode
is specialized on working with ISO 9660 filesystems on all kinds of media.


The cdrecord usage model is inspired by CD-R media, which have three
possible states of writablility and readability: blank, appendable, closed.
(I.e. no reading, reading and writing, reading only.)
Somehow xorrecord has to squeeze the states of other optical media into
this model.

The behavior of wodim and older cdrecord is not appropriate for
overwritable media. It tells that the medium is fully written (and not
supported):

  $ wodim dev=/dev/sr4 -toc
  ...
  wodim: Found unsupported DVD-RAM media.
  ...
  first: 1 last 1
  track:   1 lba:         0 (        0) 00:02:00 adr: 1 control: 4 mode: -1
  track:lout lba:   2236704 (  8946816) -1:59:74 adr: 1 control: 4 mode: -1

Old cdrecord-2.01.01a64 reports

  WARNING: Phys disk size 2314080 differs from rzone size 2236704! Prerecorded disk?
  WARNING: Phys start: 200704 Phys end 2514783
  first: 1 last 1
  track:   1 lba:         0 (        0) 00:02:00 adr: 1 control: 4 mode: -1
  track:lout lba:   2236704 (  8946816) -1:59:74 adr: 1 control: 4 mode: -1

Both is not helpful when a user or program wants to know what must be
done to make the medium writable.


On sequential media there is no such ambiguity: CD-R, unformatted CD-RW,
DVD+R, DVD-R, BD-R (if not formatted to Pseudo-Overwrite).


Have a nice day :)

Thomas