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[Libcdio-devel] Re: Retrieving DATA session from multisession audio disc

From: Thomas Schmitt
Subject: [Libcdio-devel] Re: Retrieving DATA session from multisession audio disc
Date: Wed, 17 Feb 2010 16:24:58 +0100


Eric Shattow wrote:
> How to extract the data session from a multi-session audio cd and interact
> with the resulting "offset" ISO using libcdio tools?
> $ extricate /dev/sr0 8mm-songs_to_love_and_die_by.iso
> ...
> Remember, the path table and directory structure of the iso reflect
> the fact that the ISO filesystem starts on sector 222145 (49:23:70)
> of the CD. 

Robert William Fuller wrote:
> modprobe loop
> mount -o loop,sbsector=somenumber foo.iso /mnt

-o sbsector=  points to the start block of the
desired track if it is at the original position.
But Eric's is displaced by 222145 blocks of 2 kB.

Adventurous testers could try losetup option -o
with a negative value or mount option "offset".

I'd rather propose to put the ISO image onto a
CD sized podium.
First create a placeholder of 222145 blocks
by writing one block to address 222144:

  dd if=/dev/zero \
     bs=2K count=1 seek=222144 \

Then append the ISO 9660 track content

  cat 8mm-songs_to_love_and_die_by.iso >>cd_dummy.iso

This image should be mountable on GNU/Linux by

  mount -t iso9660 -o loop,sbsector=222145 \
        cd_dummy.iso /mnt

Hopefully the placeholder becomes a sparse file
which consumes only a few KB of disk space. Be
aware that it might consume its full size when
being copied.

For the first part of Eric's question:

It should be possible to read the data track
by normal shell commands. One needs to know
where it begins. Nice to know is the size
(can be tricky to evaluate, though).

>  11: 49:23:70  222145 data   false  no
> 170: 49:44:24  223674 leadout (501 MB raw, 501 MB formatted)


  dd if=/dev/sr0 bs=2K \
     skip=222145 count=1529 \

Have a nice day :)


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