Differences between version 7 and predecessor to the previous major change of CompactDisc.
Other diffs: Previous Revision, Previous Author, or view the Annotated Edit History
| Newer page: | version 7 | Last edited on Saturday, January 31, 2009 12:23:47 pm | by LawrenceDoliveiro | Revert |
| Older page: | version 6 | Last edited on Sunday, April 29, 2007 2:43:42 pm | by LawrenceDoliveiro | Revert |
@@ -3,17 +3,17 @@
Note that the data is encoded in a very thin layer just underneath the ''label'' side of the disc; any damage to this side can cause __irreversible loss of data__. When you look at the ''shiny'' side, you are actually looking through the layer of transparent plastic which makes up most of the thickness of the disc, towards the data layer under the label. Scratches to this plastic layer can be tolerated to some extent, and there are even ways (though not necessarily reliable ones?) to repair scratches by smoothing them out.
Often used for copying LinuxDistribution~s onto and distributing at InstallFest~s.
-Standard discs hold 650[MB] or there abouts, although 700MB discs are also
common.
+Standard discs hold 650[MB] or there abouts, although 700MB discs have now become more
common.
!!! Audio Discs
The physical format of a CD and the representation of audio tracks is defined in a specification called the "Red Book". Discs and players that are certified to this specification carry the familiar "Compact Disc Digital Audio" logo, which is controlled by Philips.
The raw error rate of reading the zeroes and ones on the disc is about 1 in 1000; in audio terms, that would translate to a signal-to-noise ratio of 60dB, which is about comparable with the old audiocassettes (i.e. it would not be considered "hi-fi"). However, by the use of error-correcting codes (specifically, "Reed-Solomon Cross-Interleave Redundancy Checking"), this error rate drops to 1 in 1000000, which translates in audio terms to a signal-to-noise ratio best described as "fantastic". However, in computer terms, that is still not reliable enough for storing computer data.
Many forms of CopyControl degrade the audio quality or alter the data structures on the plastic wafer in an attempt to prevent customers using the data. By thus degrading their product, the manufacturers may no longer meet the "Red Book" standard, meaning they cannot ''legally'' be called CompactDisc~s.
-Since consumers might notice that plastic wafers which do not work in their equipment are missing the "CD" logo and so stop bying
such CopyControl~led wafers, there is an incentive for manufacturers to mislabel their discs.
+Since consumers might notice that plastic wafers which do not work in their equipment are missing the "CD" logo and so stop buying
such CopyControl~led wafers, there is an incentive for manufacturers to mislabel their discs.
So be on the lookout for things that are ''not'' CompactDisc~s which are labelled illegally while shopping.
@@ -26,16 +26,16 @@
<verbatim>
# mount /path/to/image.iso /place/to/mount -o loop
</verbatim>
-There are two competing standards to allow longer filenames and a few other things [ISO]9660 does not provide. The earlier one, originating from the [Unix] environment, is called Rock Ridge. The other one, made up my
MicrosoftCorporation, is called Joliet. (Note that some characters that are valid on [Unix] FileSystems are not allowed on Joliet discs.)
+There are two competing standards to allow longer filenames and a few other things [ISO]9660 does not provide. The earlier one, originating from the [Unix] environment, is called Rock Ridge. The other one, made up by
MicrosoftCorporation, is called Joliet. (Note that some characters that are valid on [Unix] FileSystems are not allowed on Joliet discs.)
!!! Compact Discs and your computer
For reading audio discs or writing CDs, you need access to the [CDROM] drive raw device. For a data disc, this raw device should be [mountable|mount(8)] onto the filesystem.
-Under a [Linux] OperatingSystem, these raw devices are called <tt>/dev/hd''x''
</tt> for [IDE] drives and
<tt>/dev/scd''n''</tt> for [SCSI
] drives. Under [FreeBSD] 5 and later, they're called <tt>/dev/acd''n''</tt> for [IDE] drives and ''??? (AddToMe)'' for [SCSI] drives.
+Under a [Linux] OperatingSystem, these raw devices are called <tt>/dev/hd</tt>''xn''
for [IDE] drives,
<tt>/dev/scd</tt>
''n'' for [SCSI] drives and <tt>/dev/sr
</tt>''n''
for [SATA
] drives. Under [FreeBSD] 5 and later, they're called <tt>/dev/acd''n''</tt> for [IDE] drives and ''??? (AddToMe)'' for [SCSI] drives.
See also:
* [CDRippingNotes]
* [CDWritingNotes]
