Bug#688229: Burning data DVD looks successful but mounting fails with ISOFS: Unable to identify CD-ROM format.

[Thomas Schmitt]

Hi,

> Could you please CC me

I will try to remember. :)
But maybe you better subscribe by a mail to
  688229-subscribe at bugs.debian.org


> Is there some way to simulate a burner to find out what happened?

libburn would accept burner addresses like
  stdio:/tmp/my_emulated_drive
which would behave like DVD-RAM or DVD+RW. I.e. quite different
from DVD-R or DVD+R. Nevertheless such an emulated drive would
allow to exercise the communications between libisofs and libburn,
as done by Brasero.

I do not know how to make Brasero use such a drive address.
Probably one would have to hack its source.

Another way to exercise DVD-R is to use DVD-RW. They need to get
blanked before re-use. E.g. by
  xorriso -outdev /dev/sr1 -blank deformat -eject all
This lasts as long as writing the full capacity of 4.7 GB.
(Fast blanking is possible but the DVD-RW would afterwards refuse
 to perform the write type Incremental which is used by Brasero.)


Some numbers from your reports are against my theory of a missing
start piece:

libisofs reported:
    brasero (libisofs)DEBUG : Processed 2119108 of 2119108 KB (100 %)

dvd+rw-mediainfo and xorriso -toc report a track size of
    1059568*2KB

The overall sizeis of image and track would match.
    2 * 1059568 - 2119108 = 28
The track size is aligned to a DVD ECC block of 32 KiB.

The track was written by write type Incremental. I.e. it
is supposed to bear only the bytes which were actually written,
rounded up to the next multiple of 16 blocks (= 32 KiB).

If a start piece of the image would be missing, then the track
would have to be shorter.

Grrrrr.

I assume you too live in Germany. If so:
Would the images on the DVD be non-private enough and would
you want to invest 1.45 Euro into a mail stamp in order to send
me that DVD-R for closer inspection ?
Or do you have 2 GB of internet storage from where i could
download a copy of the medium made by
  dd if=/dev/sr1 bs=2048 of=/tmp/copy_of_dev_sr1
?


> Everything worked fine with `xorriso`.
>
>         $ xorriso -md5 on -outdev /dev/sr1 -map ~/test /

Well ... Yay and Grrrr at the same time.
Yay for xorriso and the drive, Grrr for my inability to explain what
went wrong with the Brsaero DVD-R.


> The only thing I noticed, that another DVD drive, the Toshiba DVD-ROM
> SD-M1712, needed more than 25 seconds to recognize the disc.

This might be due to the fact that the medium is still appendable,
unlike the one from Brasero. I.e. you could add more files by xorriso
or growisofs.

How is recognition time with the burner ?

In order to get a closed DVD-R, you would have to use command
  -close on
E.g. with the now appendable DVD-R medium
  $ mkdir ~/test2
  $ cp ...a...few...files... ~/test2
  $ xorriso -md5 on -dev /dev/sr1 -map ~/test2 /test2 -close on

(Note that this run uses command -dev rather than -outdev in order
 to load the existing directory tree of the image and to merge it
 with the newly added file tree.)

Maybe it will then be recognized faster by the DVD-ROM.


Have a nice day :)

Thomas