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

[Eric Shattow]

The notes at http://howto-pages.org/cdwriting/11.php explain one way to do this:

"

Write the audio tracks to the CD, but in multisession mode:

# cdrecord dev=0,0 fs=4m speed=4 -v -multi -audio list_of_audio_tracks
Find out the extent of the session just written:

# cdrecord dev=0,0 -msinfo
0,148754

This information will be used when you build your ISO image with
mkisofs and the -C command line parameter (see "Multisession
CD-ROMs").
Write the data session:

# cdrecord dev=0,0 speed=8 fs=16mb -v -eject your_iso_filesystem.iso

Note that we're no longer writing audio tracks here so we can boost
the write speed.

"

I have not tried this method myself, and it does sound dated. I think
this makes sense with what we are discussing anyways.

On Thu, Feb 18, 2010 at 2:53 AM, Thomas Schmitt <address@hidden> wrote:
>
> Hi,
>
> Rocky Bernstein wrote:
> > libcdio's iso-info seems to only be able to handle reading when this
> > filesystem in the first track.
>
> This also keeps it from properly reading
> multi-session ISO 9660 from data CD.
>
>
> > It looks like there is a
> > more fundamental deficiency in the library which assumes a fixed block
> > location of the "Primary Volume Descriptor" or PVD.
>
> There are two "offset" discussed here:
>
> - The "superblock" location.
>
>  This is the block address where the track
>  starts. 16 blocks up you can expect the PVD.
>  This is addressed e.g. by
>    mount -o sbsector=$track_start
>    mkisofs -C $track_start,...
>    xorriso -load lba $track_start
>
>  You need it for reading multi-track resp.
>  multi-session images.
>
>
> - A displacement offset if the track data are
>  not stored at the old location any more.
>
>  This is to be applied to all block addresses
>  which are read from data words in the image.
>  E.g. the PVD has the address of the root
>  directory. This already needs the displacement
>  offset before it is used to read the directory
>  entries from there.
>
>
> > Also, what would help in developing such changes would be to have a *small*
> > CD image and/or extracted ISO 9660 filesystem.
>
> A displaced ISO filesystem is easy to create.
> Just give the generator program a wrong Next
> Writeable Address.
> E.g:
>
>  mkisofs -C 0,$some_offset \
>          -o displaced_image.iso \
>          /my/small/directory/tree
>
>
> If you know a recipie for creating a correct
> CD-EXTRA by help of cdrecord, then i would be
> very interested to learn it.
>
>
> Have a nice day :)
>
> Thomas
>
>
>