#37 multi-session starts where

open
nobody
None
9
2004-08-12
2004-08-12
Pat LaVarre
No

Paraphrasing Ben Fennema thoughts of 2004-05-24:

Issues finding the correct session start in
multi-session DVD's.

A recent example is:

Re: Can not read UDF CD
http://marc.theaimsgroup.com/?t=109109115700004

Hi priority because this issue interests Ben and
because linux-kernel records people feeling pain here.

Discussion

  • Pat LaVarre

    Pat LaVarre - 2004-08-16

    Logged In: YES
    user_id=964855

    See also the report of Windows Nero 6 multi-session DVD's seen not
    mountable as recently as 2.6.7:

    [ 1005077 ] kernel freeze when mouting DVD
    https://sourceforge.net/tracker/index.php?
    func=detail&aid=1005077&group_id=295&atid=100295

     
  • Nobody/Anonymous

    Logged In: NO

    Late to the game here, but if this bug still exists then I have a possible work around. "uname -a" gives:

    Linux darkstar 2.6.7 #1 Wed Jun 16 16:23:03 PDT 2004 i686 unknown unknown GNU/Linux

    Using GEAR Software to burn a multi-session UDF ver. 1.02 DVD under Linux with a file >1GB (requires multiple extents) on DVD-R (variable

    packet writing) in which the large file was first written in session 0 then appended to in session 1, attempting to mount the disc results

    in:

    # mount -t udf /dev/hdc /mnt
    mount: block device /dev/hdc is write-protected, mounting read-only
    mount: wrong fs type, bad option, bad superblock on /dev/hdc,
    or too many mounted file systems

    Attempting to specify the last session on disc (-o session=x) results in similar results:

    # mount -t udf -o session=1 /dev/hdc /mnt
    mount: block device /dev/hdc is write-protected, mounting read-only
    mount: wrong fs type, bad option, bad superblock on /dev/hdc,
    or too many mounted file systems

    Specifying session 0, which is not the last session on the disc, results in only seeing the first couple extents worth of the file. I

    suspect (did not verify) this is actually the data written in the first session (ignore the uid and gid values):

    # mount -t udf -o session=0 /dev/hdc /mnt
    mount: block device /dev/hdc is write-protected, mounting read-only
    # ls -l /mnt
    total 856574
    -r-xr-xr-x 1 4294967295 4294967295 35 2007-03-09 13:54 F35B.txt
    -r-xr-xr-x 1 4294967295 4294967295 877129728 2007-03-09 13:54 NTSC_MPEG2_1_08GB.mpg

    Now if I specify session 0 and the anchorpoint that corresponds to the anchor of the last session on the disc, then I end up with what

    appears to be valid data (notice the file sizes) and I'm able to read back the entire contents of the >1GB file. Note that I have tried

    this with 2 of the 3 anchor points for the last session, and both work just fine. I did not try the 3rd anchor point. Note also that this

    only works when I specify session 0, not when I specify the session that I want to mount. Not knowing the Linux mount utility internals

    I'm not sure if this is cause for concern, but so far it appears to be working.

    # mount -t udf -o session=0 -o anchor=601407 /dev/hdc /mnt
    mount: block device /dev/hdc is write-protected, mounting read-only
    # ls -l /mnt
    total 1142100
    -r-xr-xr-x 1 4294967295 4294967295 35 2007-03-09 13:54 F35B.txt
    -r-xr-xr-x 1 4294967295 4294967295 1169508352 2007-03-09 13:59 NTSC_MPEG2_1_08GB.mpg

    I hope this helps someone.

     
  • Nobody/Anonymous

    Logged In: NO

    Correction to my previous post: we're using udf version 1.50, NOT 1.02!

     
  • Nobody/Anonymous

    Logged In: NO

    Final comment: The Philips udf verification tool shows zero errors and zero warnings on the filesystem for the disc used below.

     

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