CDFS(4) CDFS(4)
NAME
cdfs, cddb - optical disc (CD, DVD, BD) track reader and
writer file system
SYNOPSIS
cdfs [ -d sddev ] [ -m mtpt ]
grep aux/cddb /mnt/cd/ctl | rc
aux/cddb [ -DTt ] [ -s server ] query diskid ntracks
track0id ...
DESCRIPTION
Cdfs serves a one and a half level directory mounted at mtpt
(default /mnt/cd) that provides access to the tracks on
discs placed in the disc reader or writer named by sddev
(default /dev/sdD0, see sd(3)). Any MMC-compliant compact
disc (CD), DVD, or Blu-ray disc (BD) drive should work. On
DVDs and BDs, access to data tracks only is implemented.
The top level directory contains one file per disc track.
The files are named cNNN, where c is a type character (a for
audio tracks and d for data tracks) and NNN is the track
number.
If the device can write discs and contains a writable disc,
the top-level directory also contains an empty directory wd
and, for CDs only, an empty directory wa. Files created in
these directories appear in the top-level directory as new
data or audio tracks, respectively, regardless of name.
At any time, any number of tracks may be open for reading or
a single track may be open for writing. Writing a disc
track is a quasi-real-time operation: the disc writer should
be kept saturated with new data to avoid buffer underruns,
but modern drives will be told to cope with underruns trans-
parently. To ensure saturation, copying from a file system
stored on local disk or memory is recommended.
BD-R discs are `formatted' upon first use, for sequential
writing with spare sectors for hardware defect management,
so BD drives should not report errors when writing BD-R
discs; any such errors may be a sign that the laser of an
old drive is fading.
To fixate a disc (close a recordable disc by writing its
permanent table of contents), simply remove the wa or wd
directory. The directory removed selects whether the disc
is fixated as an audio or data disc; since each track car-
ries its own type information, very few readers care which
fixation type was used. Rewritable discs do not require
fixation.
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CDFS(4) CDFS(4)
The top level directory also contains a ctl file, into which
control messages may be echoed. The current control mes-
sages are:
format Format the rewritable disc (-RW or -RE) in the
drive before initial use.
blank Blank the entire rewritable disc in the drive.
quickblank Blank only the table of contents on the rewrit-
able disc in the drive.
eject Eject the disc in the drive.
ingest Ingest a disc into the drive.
speed kbps Set the reading and writing speed to use, in
units of 1,000-bytes-per-second. A value of
`best' requests the optimal speed for the cur-
rent drive and disc. CD `1x' speed is 154; DVD
`1x' speed is 1350; BD `1x' speed is 4608.
Drives may round down the speed to one they sup-
port. To set reading and writing speeds sepa-
rately, prefix the speeds with read or write, as
in speed write 8192 or speed read 16384 write
8192. Note that most drives reset the reading
and writing speed each time a new disc is
inserted.
Reading the ctl file yields information about the drive. If
the drive contains an audio CD, the first line will be an
aux/cddb command that can be run to query an internet CD
database to get a table of contents. Subsequent lines con-
tain the current and maximum reading and writing speeds.
Additional lines may further describe the current disc.
Aux/cddb takes 4 optional arguments. The -s option makes
aux/cddb use server for the query instead of
`freedb.freedb.org'. The -D option causes the raw database
response from the server to be dumped to standard output.
The -t option causes the time of each track to be appended
to the normal output. -T is like -t but prints a final line
with the total time.
EXAMPLES
Backup to a BD-R disc:
9fs boot
cdfs
tar cf /mnt/cd/wd/x /n/boot
Copy the audio tracks from a CD:
cdfs -d /dev/sd05
mkdir /tmp/songs
cp /mnt/cd/a* /tmp/songs
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CDFS(4) CDFS(4)
Copy the tracks onto a blank CD inserted in the drive, and
then fixate the disk as an audio CD.
cp /tmp/songs/* /mnt/cd/wa
rm /mnt/cd/wa
SOURCE
/sys/src/cmd/cdfs
SEE ALSO
pump(1), sd(3), 9660srv (in dossrv(4)), mk9660(8)
http://www.t10.org optical disc interface standards,
notably Multi-Media Commands (MMC)
BUGS
Fixating a BD-R disc records only the first track in the
disc's TOC. Any other tracks are still there and their data
accessible via sd(3). There's no need to fixate data discs,
except to prevent adding new tracks.
Closing a just-written DVD-R track can take minutes while
the drive burns the unused part of the track reservation
(for the whole disc). Thus only a single DVD-R track can be
written on a DVD-R disc; use other media if you need more
than one track per disc.
There are too many combinations of optical media, each with
unique quirks, approximately the cross-product of these
tuples: (CD DVD- DVD+ BD), (-ROM -R -RW), (single-layer
dual-layer), plus oddities like DVD-RAM. Triple- and quad-
layer BD drives and discs are starting to appear.
Only MMC-compliant disc readers and writers are supported,
but it would be easy to add support for early CD writers if
desired.
Cdfs can take some seconds to figure out that it has a BD in
the drive and how many layers are on the disc.
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