path: root/DOCS/xml/en/cd-dvd.xml

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<chapter id="cd-dvd">
<title>CD/DVD usage</title>

<sect1 id="drives">
<title>CD/DVD drives</title>
<para>
Linux documentation excerpt:
</para>

<para>
Modern CD-ROM drives can attain very high head speeds, yet some CD-ROM drives
are capable of running at reduced speeds. There are several reasons that might
make you consider changing the speed of a CD-ROM drive:
</para>

<itemizedlist>
<listitem><para>
There have been reports of read errors at high speeds, especially
with badly pressed CD-ROMs. Reducing the speed can prevent data loss under
these circumstances.
</para></listitem>

<listitem><para>
Many CD-ROM drives are annoyingly loud, a lower speed may reduce the noise.
</para></listitem>
</itemizedlist>

<para>
You can reduce the speed of IDE CD-ROM drives with <command>hdparm</command> or a
program called <command>setcd</command>. It works like this:
<screen>hdparm -E <replaceable>[speed]</replaceable> <replaceable>[cdrom device]</replaceable></screen>
<screen>setcd -x <replaceable>[speed]</replaceable> <replaceable>[cdrom device]</replaceable></screen>
</para>

<para>
If you have root privileges the following command may also help:
<screen>echo file_readahead:2000000 &gt; /proc/ide/<replaceable>[cdrom device]</replaceable>/settings</screen>
</para>

<para>
This sets prefetched file reading to 2MB, which helps with scratched CD-ROMs.
If you set it to too high, the drive will continuously spin up and down, and
will dramatically decrease the performance.
It is recommended that you also tune your CD-ROM drive with <command>hdparm</command>:
<screen>hdparm -d1 -a8 -u1 <replaceable>cdrom device</replaceable></screen>
</para>

<para>
This enables DMA access, read-ahead, and IRQ unmasking (read the <command>hdparm</command>
man page for a detailed explanation).
</para>

<para>
Please refer to &quot;<filename>/proc/ide/<replaceable>cdrom device</replaceable>/settings&quot;</filename>
for fine-tuning your CD-ROM.
</para>

<para>
SCSI drives do not have a uniform way of setting these parameters (Do you know one?
Tell us!) There is a tool that works for
<ulink url="http://das.ist.org/~georg/">Plextor SCSI drives</ulink>.
</para>

<para>FreeBSD:</para>
<para>Speed: <command>cdcontrol [-f <replaceable>device</replaceable>] speed <replaceable>speed</replaceable></command></para>
<para>DMA: <command>sysctl hw.ata.atapi_dma=1</command></para>
</sect1>

<sect1 id="dvd">
<title>DVD playback</title>
<para>
For the complete list of available options, please read the man page.
The Syntax for a standard Digital Versatile Disc (DVD) is as follows:
<screen>mplayer dvd://<replaceable>&lt;track&gt;</replaceable> [-dvd-device <replaceable>&lt;device&gt;</replaceable>]</screen>
</para>

<para>
Example:
<screen>mplayer dvd://<replaceable>1</replaceable> -dvd-device <replaceable>/dev/hdc</replaceable></screen>
</para>

<para>
The default DVD device is <filename>/dev/dvd</filename>. If your setup
differs, make a symlink or specify the correct device on the command
line with the <option>-dvd-device</option> option.
</para>

<formalpara>
<title>New-style DVD support (mpdvdkit2)</title>
<para>
<application>MPlayer</application> uses <systemitem>libdvdread</systemitem> and
<systemitem>libdvdcss</systemitem> for DVD decryption and playback. These two
libraries are contained in the <filename class="directory">libmpdvdkit2/</filename>
subdirectory of the <application>MPlayer</application> source tree, you do not have
to install them separately. We opted for this solution because we had to fix a
<systemitem>libdvdread</systemitem> bug and apply a patch which adds
<emphasis role="bold">cracked CSS keys caching support</emphasis> to
<systemitem>libdvdcss</systemitem> This results in a large speed increase because the
keys do not have to be cracked every time before playing.
</para>
</formalpara>

<para>
<application>MPlayer</application> can also use system-wide <systemitem>libdvdread</systemitem>
and <systemitem>libdvdcss</systemitem> libraries, but this solution is
<emphasis role="bold">not</emphasis> recommended, as it can result in bugs,
library incompatibilities and slower speed.
</para>

<note><para>
In case of DVD decoding problems, try disabling supermount, or any other such
facilities.
</para></note>

<formalpara>
<title>DVD structure</title>
<para>
DVD disks have 2048 bytes per sector with ECC/CRC. They usually have an UDF
filesystem on a single track, containing various files (small .IFO and .BUK
files and big (1GB) .VOB files). They are real files and can be copied/played
from the mounted filesystem of an unencrypted DVD.
</para>
</formalpara>

<para>
The .IFO files contain the movie navigation information (chapter/title/angle
map, language table, etc) and are needed to read and interpret the .VOB content
(movie). The .BUK files are backups of them. They use
<emphasis role="bold">sectors</emphasis> everywhere, so you need to use raw
addressing of sectors of the disc to implement DVD navigation or decrypt the
content.
</para>

<para>
DVD support needs raw sector-based access to the device. Unfortunately you must
(under Linux) be root to get the sector address of a file. That's why we don't
use the kernel's filesystem driver at all, instead we reimplement it in
userspace. <systemitem>libdvdread</systemitem> 0.9.x and
<systemitem>libmpdvdkit</systemitem> do this. The kernel UDF filesystem driver
is not needed as they already have their own builtin UDF filesystem driver.
Also the DVD does not have to be mounted as only the raw sector-based access is
used.
</para>

<para>
Sometimes <filename>/dev/dvd</filename> cannot be read by users, so the
<systemitem>libdvdread</systemitem> authors implemented an emulation layer
which transfers sector addresses to filenames+offsets, to emulate raw
access on top of a mounted filesystem or even on a hard disk.
</para>

<para>
<systemitem>libdvdread</systemitem> even accepts the mountpoint instead of
the device name for raw access and checks <filename>/proc/mounts</filename>
to get the device name. It was developed for Solaris, where device names
are dynamically allocated.
</para>

<para>
The default DVD device is <filename>/dev/dvd</filename>. If your setup differs,
make a symlink, or specify the correct device on the command line with the
<option>-dvd-device</option> option.
</para>

<formalpara>
<title>DVD authentication</title>
<para>
The authentication and decryption method of the new-style DVD support is done
using a patched <systemitem>libdvdcss</systemitem> (see above). The method can
be specified through the environment variable <envar>DVDCSS_METHOD</envar>,
which can be set to key, disk or title.
</para>
</formalpara>

<para>
If nothing is specified it tries the following methods (default: key,
title request):
</para>

<orderedlist>
<listitem><para>
<emphasis role="bold">bus key</emphasis>: This key is negotiated during
authentication (a long mix of ioctls and various key exchanges, crypto
stuff) and is used to encrypt the title and disk keys before sending them
over the unprotected bus (to prevent eavesdropping). The bus key is needed
to get and predecrypt the crypted disk key.
</para></listitem>

<listitem><para>
<emphasis role="bold">cached key</emphasis>: <application>MPlayer</application>
looks for already cracked title keys which are stored in the
<filename class="directory">~/.mplayer/DVDKeys</filename> directory (fast ;).
</para></listitem>

<listitem><para>
<emphasis role="bold">key</emphasis>: If no cached key is available,
<application>MPlayer</application> tries to decrypt the disk key with a set
of included player keys.
</para></listitem>

<listitem><para>
<emphasis role="bold">disk</emphasis>: If the key method fails
(e.g. no included player keys), <application>MPlayer</application>
will crack the disk key using a brute force algorithm. This process
is CPU intensive and requires 64 MB of memory (16M 32Bit entries hash
table) to store temporary data. This method should always work (slow).
</para></listitem>

<listitem><para>
<emphasis role="bold">title request</emphasis>: With the disk key
<application>MPlayer</application> requests the crypted title keys,
which are inside <emphasis>hidden sectors</emphasis> using <systemitem>ioctl()</systemitem>.
The region protection of RPC-2 drives is performed in this step and may fail on such drives.
If it succeeds, the title keys will be decrypted with the bus and disk key.
</para></listitem>

<listitem><para>
<emphasis role="bold">title</emphasis>: This method is used if the title
request failed and does not rely on any key exchange with the DVD drive.
It uses a crypto attack to guess the title key directly (by finding a
repeating pattern in the decrypted VOB content and guessing that the
plain text corresponding to the first encrypted bytes is a continuation
of that pattern). The method is also known as &quot;known plaintext attack&quot;
or &quot;DeCSSPlus&quot;. In rare cases this may fail because there is not
enough encrypted data on the disk to perform a statistical attack or because
the key changes in the middle of a title. This method is the only way to
decrypt a DVD stored on a hard disk or a DVD with the wrong region on an
RPC2 drive (slow).
</para></listitem>
</orderedlist>

<para>
RPC-1 DVD drives only protect region settings through software. RPC-2 drives
have a hardware protection that allows 5 changes only. It might be
needed/recommended to upgrade the firmware to RPC-1 if you have a RPC-2 DVD
drive. You can try finding firmware upgrades for your drive on the internet,
<ulink url="http://forum.rpc-1.com/dl_all.php">this firmware forum</ulink>
may be a good starting point for your search.
If there is no firmware upgrade available for your device, use the
<ulink url="http://linvdr.org/projects/regionset/">regionset tool</ulink>
to set the region code of your DVD drive (under Linux).
<emphasis role="bold">Warning</emphasis>: You can only set the region 5 times.
</para>
</sect1>

<sect1 id="vcd">
<title>VCD playback</title>
<para>
For the complete list of available options, please read the man page. The Syntax for a
standard Video CD (VCD) is as follows:
<screen>mplayer vcd://<replaceable>&lt;track&gt;</replaceable> [-cdrom-device <replaceable>&lt;device&gt;</replaceable>]</screen>
Example:
<screen>mplayer vcd://<replaceable>2</replaceable> -cdrom-device <replaceable>/dev/hdc</replaceable></screen>
The default VCD device is <filename>/dev/cdrom</filename>. If your setup
differs, make a symlink or specify the correct device on the command line
with the <option>-cdrom-device</option> option.
</para>

<note><para>
At least Plextor and some Toshiba SCSI CD-ROM drives have horrible performance
reading VCDs. This is because the CDROMREADRAW <systemitem>ioctl</systemitem>
is not fully implemented for these drives. If you have some knowledge of SCSI
programming, please <ulink url="../../tech/patches.txt">help us</ulink>
implement generic SCSI support for VCDs.
</para></note>

<para>
In the meantime you can extract data from VCDs with
<ulink url="http://miketeo.net/links/readvcd-0.3.tgz">readvcd</ulink>
and play the resulting file with <application>MPlayer</application>.
</para>

<formalpara>
<title>VCD structure</title>

<para>
A Video CD (VCD) is made up of CD-ROM XA sectors, i.e. CD-ROM mode 2
form 1 and 2 tracks:</para>
</formalpara>

<itemizedlist>
<listitem><para>
The first track is in mode 2 form 2 format which means it uses L2
error correction. The track contains an ISO-9660 filesystem with 2048
bytes/sector. This filesystem contains VCD metadata information, as
well as still frames often used in menus. MPEG segments for menus can
also be stored in this first track, but the MPEGs have to be broken up
into a series of 150-sector chunks. The ISO-9660 filesystem may
contain other files or programs that are not essential for VCD
operation.
</para></listitem>

<listitem><para>
The second and remaining tracks are generally raw 2324 bytes/sector
MPEG (movie) tracks, containing one MPEG PS data packet per
sector. These are in mode 2 form 1 format, so they store more data per
sector at the loss of some error correction. It is also legal to have
CD-DA tracks in a VCD after the first track as well.
On some operating systems there is some trickery that goes on to make
these non-ISO-9660 tracks appear in a filesystem. On other operating
systems like GNU/Linux this is not the case (yet). Here the MPEG data
<emphasis role="bold">cannot be mounted</emphasis>. As most movies are
inside this kind of track, you should try <option>vcd://2</option>
first.</para></listitem>

<listitem><para>
There exist VCD disks without the first track (single track and no filesystem
at all). They are still playable, but cannot be mounted.
</para></listitem>

<listitem><para> The definition of the Video CD standard is called the
Philips "White Book" and it is not generally available online as it
must be purchased from Philips. More detailed information about Video
CDs can be found in the
<ulink url="http://www.vcdimager.org/pub/vcdimager/manuals/0.7/vcdimager.html#SEC4">vcdimager documentation</ulink>.
</para></listitem>

</itemizedlist>

<formalpara>
<title>About .DAT files</title>
<para>
The ~600 MB file visible on the first track of the mounted VCD is not a real
file! It is a so called ISO gateway, created to allow Windows to handle such
tracks (Windows does not allow raw device access to applications at all).
Under Linux you cannot copy or play such files (they contain garbage). Under
Windows it is possible as its iso9660 driver emulates the raw reading of
tracks in this file. To play a .DAT file you need the kernel driver which can
be found in the Linux version of PowerDVD. It has a modified iso9660 filesystem
(<filename>vcdfs/isofs-2.4.X.o</filename>) driver, which is able to emulate the
raw tracks through this shadow .DAT file. If you mount the disc using their
driver, you can copy and even play .DAT files with <application>MPlayer</application>. But it will not
work with the standard iso9660 driver of the Linux kernel! Use
<option>vcd://</option> instead. Alternatives for VCD copying are the
new <ulink url="http://www.elis.rug.ac.be/~ronsse/cdfs/">cdfs</ulink> kernel
driver (not part of the official kernel) that shows CD sessions as image files and
<ulink url="http://cdrdao.sf.net/">cdrdao</ulink>, a bit-by-bit
CD grabbing/copying application.
</para>
</formalpara>
</sect1>
</chapter>