[plug] CUE/BIN vs ISO

[Cameron Patrick]

Evenin' all,

On Fri, Sep 12, 2003 at 06:08:19PM +0800, Weirdo wrote:
| From my experiences dd does a binary duplication of the surface. This 
| means that it is not a ISO but a BIN. The audio on a data cd is still 
| binary so it comes with every thing else. When you mount the BIN file using 
| ISO9660 it mounts the ISO portion of it as it is reading the file in 
| exactly the same way as if it was /dev/cdrom. Audio is Data, it is binary 
| data, other wise how can it be stored in a binary format? dd if=/dev/cdrom 
| of=~/somefile.bin will get every binary bit from the surface including 
| audio.

I think you may be mistaken.  Have you actually tested this?  Audio and
data are stored differently on a CD; audio has a sector size of 2352
bytes as opposed to 2048 bytes for data. (Source: man cdrecord)  Data
tracks on a CD have extra information for exact positioning and error
correction.  Reading a specific sector on an audio track, on the other
hand, is tricky as the positioning is only approximate and different
drives have different offsets. (Source: /usr/share/doc/cdparanoia, see
also the web site for Exact Audio Copy which explains - or at least used
to - a lot of the issues involved in ripping audio CDs without losing
data.)

dd'ing /dev/cdrom will only copy /one/ data track; this is fine for most
data CDs which only contain one track, but specialised software is
needed to get an exact copy of a CD containing audio or >1 track.

| This WON'T work for a CSS DVD as the encryption stops the DVD drive 
| from allowing extraction without a CSS key (some dvd drives probably will 
| allow it).

Possibly, no experience with attempting to do this.  Certainly, you
can't /write/ a DVD with a CSS key as consumer DVD media isn't writable
in those areas.

| Think about it, how else can things like playstation 1 games, 'special' 
| audio cds and the likes all get copyed when the OS can't read the file 
| system?

In the case of audio CDs, special magic ioctl()s :-)  No idea about
video CDs or playstation games, but presumably they are either data CDs
in disguise or equivalent to audio.

Note that being able to read the data off a data track is a separate
issue entirely to being able to read the file system off a CD.  I could,
e.g. burn an ext2 file system onto a CD, and Windows would be incapable
of reading it as it doesn't understand ext2, but it would still be able
to read the data track off the CD with its equivalent of dd.  A better
example, perhaps, would be considering the case of a Linux kernel which
doesn't have ISO9660 support compiled in; it would be unable to mount
the CD as it can't read ISO9660 but you would be able to dd the data
track to a file with no worries.

| p.s. If you disagree with anything said and can prove it then please do. I 
| am going mainly on experience as part of my work involves making exact 
| images of cds for storage.

Hrmm.  Above is my experience, perhaps you're mis-remembering stuff?

| p.p.s In regards to getting a cd sample, if it an audio cd chances are 
| their will be errors when it gets read. A data cd will get re-read until it 
| is read without errors, and audio cd it is usually a single bit every now 
| and then and can't be heard but the output file will be different. When I 
| get time i will write about this in more depth and post it.

Wrong again, I believe - at least if you're using software like
cdparanoia or EAC.  Some CD extraction software could well be less exact
and 'fudge' sectors with read errors or jitter[1].  Note that, as I
mentioned above, there /are/ issues regarding the starting sector, and
this varies from drive to drive but my understanding is that this error
is a function of the drive in question but /not/ of the disc or the
particular attempt to read it.

Regards,

Cameron.

[1] Incidentally, does someone here have a (pointer to a) good
explanation of what jitter is?  I've seen lots of references to it in
the context of CD ripping but no clear explanation of what it is or why
it matters?

_______________________________________________
plug mailing list
plug at plug.linux.org.au
http://mail.plug.linux.org.au/cgi-bin/mailman/listinfo/plug