PC Hardware in a Nutshell, 3rd Edition [Electronic resources] نسخه متنی

11.11 Special Problems and Applications

Once you have your CD writer and software configured properly,
burning CDs is usually a pretty straightforward process. There are,
however, some special situations that deserve comment. The following
sections detail some of the unusual situations you may encounter.

11.11.1 Copy-Protected CDs

This

was a very nice
section. We provided complete instructions for circumventing the
various copy-protection methods that manufacturers use to make life
difficult for honest users. But you'll never read
that material. Why? Because we don't want to end up
like Dmitri Sklyarov, who was imprisoned under the Digital
Millennium Copyright Act (DMCA)
simply because he exercised his First Amendment right to free speech.
(And please don't ask us to email you the deleted
text. We can't afford to take that risk.)

The sole purpose of the DMCA is to prevent all of us from doing
things we have the right to dosuch as making backup copies of
the CDs and DVDs we buyand saying things we have the right to
saysuch as how to make those backup copies. The DMCA was
bought and paid for by the RIAA
(Recording Industry Association of America) and
MPAA (Motion Picture Association of
America), and benefits no one except the music and movie
industries.

The definition of an honest politician is one who stays bought, but
we nevertheless hope the monstrosity called the DMCA can be
overturned. There are several things you can and should do to protect
your own interests. Write or call your representatives and senators
to complain about DMCA and demand it be repealed. Join the Electronic
Frontier Foundation (http://www.eff.org) and support their efforts
to preserve free speech. Hit the MPAA and RIAA where it hurts.
Boycott their products, particularly those that are copy-protected.
Make it clear to the MPAA and RIAA that their insane insistence on
treating their customers as thieves is offensive, and that you
won't put up with it.

11.11.2 Making Copies of Copies

Although it surprises many
peopleit certainly surprised usthe CDs you make in your
burner are not necessarily exact copies of the source CD. For audio
CDs, this usually isn't a problem. An occasional
dropped or flipped bit will probably be inaudible. But for data CDs,
it can be a major problem. We found this out while playing with a new
burner. We duped the original FrontPage CD, and were able to install
FrontPage from the dupe. But when we duped the dupe and then tried to
install from the second-generation copy, Setup returned file read
errors. Doing a binary compare on those files told the sad truth: the
files were identical on the original CD and the first-generation
copy, but differed on the second-generation copy.

Remember that CDs depend heavily on error-correction and detection
code. All CD formats use 3,234-byte physical sectors, which allocate
2,352 bytes to data and the remainder to control and error correction
data. Audio CDs use the entire 2,352 bytes for audio data. Yellow
Book Mode 1 (data) CDs use only 2,048 bytes for data and allocate the
remaining 304 bytes to another ECC layer. The problem arises because
of the different ways that CD burners and software read and write
Mode 1 data:

The drive reads the
entire 2,352 byte sector as a raw bit stream and writes that raw data
to the destination device. Any data read errors in either the data
segment or the ECC segment are written literally to the destination.
Working in this mode, generational degradation can overwhelm the
ability of ECC to correct errors and result in a CD that returns read
errors or contains corrupted files. This may occur as early as a
second-generation copy, and almost certainly after several
generations.

The drive reads
only the 2,048 byte data segment, using the ECC segment to verify the
data and correct it if necessary. The drive then recalculates the
proper ECC segment for that data segment and writes the original data
segment with the new ECC segment to the destination disc.

This means it is impossible to ensure an exact copy of any CD that
uses 2,352 byte data segments (audio CDs) or 2,336 byte data segments
(Mode 2 data CDs) because those segments contain no sector-level ECC
data. Fortunately, Mode 2 CDs are rare, and you can copy the common
Mode 1 data CDs reliably by using cooked mode, assuming that your
drive and software support it. To minimize copying problems, use the
following guidelines:

For Red Book (audio) CDs, use an original (pressed) CD as the source.
There is no reliable way to make a copy of an audio CD that is itself
a copy. When copying original source CDs, note that some drives
disable some error-correcting features during digital audio
extraction, or may use error correction only during DAE at 1X.
Experiment to determine the optimum recording speed for best sound
quality. Differences are subtle, particularly with recent drives and
media, but they do exist. Some people swear you should always dupe
audio CDs at 1X (or 2X or 4X), but the truth is that the optimum
speed depends on the drive and media. Drive A may make the best dupes
with Media A at 1X and with Media B at 4X, while Drive B may be
exactly the opposite. Test with each drive and each time you change
media.

For Yellow Book Mode 2 data CDs, always use an original CD as the
source. There is no reliable way to make a copy of a Mode 2 CD that
is itself a copy. If you must copy a Mode 2 copy, do a file-by-file
binary compare afterward to verify the copy.

For Yellow Book Mode 1 data CDs, either use the original CD as the
source (using either raw or cooked mode), or use cooked mode when
copying from a source CD that is itself a dupe. Also note that
problems may arise if the source dupe was made in raw mode rather
than cooked mode.

11.11.3 Creating and Using a Bootable CD-R Disc

If your system and drive support
the El Torito Specification (http://www.phoenix.com/resources/specs-cdrom.pdf),
which allows booting from CD, a bootable CD can be a useful emergency
fallback. The process required to create a bootable CD varies
according to the mastering software package you use. See the
documentation for details.

To boot from CD, the CD/DVD-ROM drive and system BIOS must support CD
as a boot device, which nearly all recent models do. To set your
system to boot from CD, run BIOS Setup and locate an option named
"Boot Sequence" or something
similar. That option will typically be set to something like
"A:, C:, CD-ROM, SCSI" by default.
Insert the bootable CD, change the boot sequence to make the CD-ROM
the first boot device, and restart the system. The system will boot
from the CD, which it will recognize as drive A:. (The actual FDD
will become B:.)

11.11.4 Creating an AutoRun CD-R Disc

At times it's useful to
create a CD that, when inserted in the drive, automatically loads and
runs a specified program or document. For example, you can distribute
HTML content on a CD that automatically invokes the
user's browser and loads

indexl . The only thing necessary to enable
AutoRun for program files is to put a properly formatted

AutoRun.inf file in the root directory of that
CD.

AutoRun.inf is a plain ASCII text file with
the following syntax:

[autorun]
Open=CmdLine

Inserting a CD that contains

Notepad.exe and

Indexl in the root directory and the
following AutoRun.inf:

[autorun]
Open=notepad.exe indexl

causes Windows to AutoRun

Notepad.exe and load
Indexl into it. You can
optionally specify a path before the program or document name.

AutoRun.inf supports many more options, which
are documented at http://www.microsoft.com/msj/0998/win320998.aspx.

Unfortunately, AutoRun does not honor file associations, which makes
it difficult to invoke the user's browser to run an
HTML source file automatically. There are several workarounds for
this problem, but the one we prefer is the small utility

Autohtml.exe , developed by Mark Trescowthick and
Ross Mack, which is available for download at http://www.avdf.com/oct98/art_ot005l.
That page includes full instructions for using the utility.

Repeatedly burning CDs while you are testing your custom

AutoRun.inf is time-consuming and wasteful. One
alternative is to modify the registry to allow AutoRun to work on a
floppy disk. As always, back up before making changes to the
registry, and proceed with caution. To make this change, which works
on Windows NT/2000/XP and Windows 9X systems, run

Regedit.exe and locate the value entry
NoDriveTypeAutoRun, which resides in the key

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer .
Double-click the value entry to edit the value.

Windows actually stores a 4-byte value, but only the following binary
digits of the first byte are meaningful. Those digits are used as a
binary bitmap, as follows:

Bit        Type
0        DRIVE_UNKNOWN
1        DRIVE_NO_ROOT_DIR
2        DRIVE_REMOVABLE
3        DRIVE_FIXED
4        DRIVE_REMOTE
5        DRIVE_CDROM
6        DRIVE_RAMDISK

By default, this bit mask is set to 10010101 (95H), which disables
AutoRun for DRIVE_UNKNOWN, DRIVE_REMOVABLE, and DRIVE_REMOTE. The
high-order bit is also set to disable AutoRun for reserved future
devices. (1=disable Autorun; 0=enable it.) Change this bit mask to
10010001 (91H) to enable AutoRun for removable drives, including
floppy diskette drives and Zip drives. Save the change and restart
the computer. A floppy disk does not AutoRun when inserted because
the floppy drive cannot notify Windows that the disk has been
inserted. However, you can manually AutoRun that floppy by
right-clicking the drive icon and choosing AutoPlay.

11.11.5 Packet Writing with Linux

Beginning with the 2.4 kernel,
Linux offers limited packet-writing support. The 2.4 and 2.5 kernels
have no native support for packet writing, but a kernel patch is
available from the Linux UDF Project (http://sourceforge.net/projects/linux-udf)
that adds basic packet-writing functions. The kernel patch should
work with any CD-(M)RW drive that supports packet writing. As we
write this, the major limitations of the patch are that it supports
only CD-RW media and fixed-length packet writing.

To enable packet writing under Linux, take the following steps:

Download the latest version of the patch from kernel.org and apply it.

Configure the kernel by selecting packet support in the block device
section and UDF support in the filesystem section.

Compile the kernel and modules, install the kernel, and reboot the
system.

Download the latest version of cdrwtool, which is
needed to format CD-RW discs.

Use the command make lib tools udf.o install to
compile and install UDF support.

Format a new CD-RW disc using the command cdrwtool
-d /dev/<device> -q.

Use the command ls /dev/pk* to verify that
/dev/pktcdvd0 exists. If it doesn't, use the command
mknod /dev/pktcdvd0 b 97 0 to create it.

Use the command pktsetup /dev/pktcdvd0
/dev/<device> to set up the CD writer.

Use the command mount /dev/pktcdvd0 to mount the
device, at which point you should be able to read from and write to
the drive.