[Debburn-devel] CD-Extra issues

[Thomas Schmitt]

Hi,

> [root directory record in PVD:]
>         char extent                     [ISODCL (3, 10)];       dc  71  04
00  00  04  71  dc
> And 0x471dc is the bogus extend from above iso_directory_record.

So already the address of the root directory's member list
is faulty.
Indeed no need to send me the start blocks of the filesystem.


> Something in my analysis is not quite right though.  I've manually
> decoded interleave as 0 but the "Interleaved files not (yet) supported."

It's not the Interleave Gap Size and File Unit Size of the
root directory record, but the random bytes which it reads
when interpreting the MP3 data as first directory record
of the root directory list.


> The first block of the 2nd session is 291114 / 0x4712a, that is the root dir
> is located at offset 0x471dc - 0x4712a = 0xb2.  But for an fs built with
> -C 0,0 (or without -C) the root dir is stored at 0x1c.  That's a difference
> of 0x96 which is 150.  And 150 is the first argument to mkisofs -C
> 150,291114.

Interesting observation.
The first argument of mkisofs option -C is supposed to be used
with option -M, which loads an ISO directory tree for the purpose
of adding more files to it.
You did not use -M. So i assumed "150" was ignored.

The number 291114 is a prediction at what block the CD drive
will start to write the next session. (A waste of several MB between
the end of the previous session and the new start is normal.
The CD drive decides about this.)
291114 was a correct prediction since you really found the primary
volume descriptor at block 291114 + 16.

So it seems that mkisofs (genisoimage ?) took the parameter 150
as additional offset for address pointers in the ISO image.


If you are curious, try what happens if you prepare the audio part
so that wodim -msinfo tells  150,something  but replace the 150
by 0 when applying this reply to mkisofs/genisoimage.

Experiments for my own software:

- Do
    xorriso -as cdrecord dev=/dev/sr0 -msinfo
  or
    cdrskin dev=/dev/sr0 -msinfo
  return  150,something  too ?

- Does
    xorriso -as mkisofs -o cd/mp3.iso -C 150,something -r -J cd/*.mp3
  yield different results than
    xorriso -as mkisofs -o cd/mp3.iso -C 0,something -r -J cd/*.mp3

(For burning one could use
    xorriso -as cdrecord dev=/dev/sr0 cd/mp3.iso
 or
    cdrskin dev=/dev/sr0 cd/mp3.iso
)

I will try these experiments myself after learning to fake a .toc
that is digestible for cdrdao.
Nevertheless i would also be interested in learning about your
experience with xorriso and cdrskin.


Have a nice day :)

Thomas