800 MB CDs 5/23/02 13:59
On the way to XCD - or how to turn 700MB CDs into 800MB ones
The idea is certainly fascinating. Despite DVD-R becoming more and more affordable regular CD-Rs are still the storage media of choice
for most of us. As you may know, both VCD and SVCD can actually contain 800MB of movie data on a regular 700MB data disc. Why? Error
correction is the keyword. Regular computer data CDs contain a lot of error protection, so your data won't get lost if you have some
scratches on a CD. But the data on the CD itself has no error correction. If you start swapping bits in an executable file you have on a CD the
file will no longer work. On the other hand, VCD and SVCD stream have some built-in protection so an additional protection on the data
storage medium is no longer needed, which frees up space otherwise used for error correction. Those of you who have had a closer look
at their burning program may have noticed that (S)VCDs are burned in mode2 whereas regular data CDs are burned in mode1.
Many people have tried to burn AVIs in mode2 mode only to fail. The burning programs are smart enough to realize that this isn't a good
idea. AVI, WAV and most fileformats in general do not have error correction or even only error detection mechanisms. So if the support
media does not offer this protection then once there is an error your files are lost forever. Clearly not a very thing, especially since
errors tend to become more frequent as time goes by, so while your files may work just fine for the first couple of months, the day you
want to print a very important document that you stored on a mode2 CD again, you can no longer read it.
New multimedia containers like ogm or mcf already offer (or will offer in the case of mfc which is still in development) error correction so
an additional level of protection is no longer needed. So let's burn our ogms as mode2 then..
WAIT! There's a catch and you should not use whatever is written in this document later on without having read this passage: The tools
presented here are for test purposes only. While formats like ogm offer some error resilience there's still an additional level of
protection needed. A player needs to know what files it is dealing with. This info is usually stored at the beginning or the end of a file. If
you have an unrecoverable error in the middle of the movie you may see a couple of blocks which may annoy you a little but you can still
use the disc. However, if the same error occurs in the part of the file where the info needed by the player is stored the file becomes
unusable. So this info would have to be stored in a mode1 part of the disc and that's currently not possible. Mode2 also doesn't allow you
to have exact filesizes so files are being padded to span a known number of sectors but the real size would have to be stored somewhere
and that's currently not implemented. Last but not least for compatibility reasons the mode2 files will have an 8.3 naming convention so if a
filename is longer the full name has to be stored somewhere. Obviously, eventually these problems are all going to be resolved but for
the time being bear them in mind. Do not use mode2 CDs to store any data that you cannot afford to lose.
It all started with a thread about putting 800MB AVIs on a 700MB CD in my forum and in time we got what's now known as Mode2 CD
Maker, by DeXT. As you can see the tool was originally designed to create MFC CDs but it has evolved since. The name MFC-CD seemed to
be too closely associated with the MCF format so there was a poll in my forum and the name XCD was eventually chosen. Mode 2 CD Maker
can create a mode2 image file that you can burn using any .cue/.bin capable burning program. Initially burning these images wasn't of
much use as you had to use another program to extract the files again. Avih came up with a filter that allows you to read these files directly
off the disc. You may recall the news about this filter, initially it read the whole file into memory and you had to use one filter for every
type of media but all these problems have been solved since. There's just one remaining issue.. not all drives seems to be compatible to the
filter. Some DVD-ROMs may refuse to play such files, but usually updating the firmware can fix this problem. I tested it on a Pioneer 16x
DVD-ROM and had no problems whatsoever.
Currently XCD is still under heavy developments, the tools I'm going to present are just a starting point and I expect to see much more in
the future. Oh, btw, XCD is an open source project hosted on sourceforge. If you're a developer and interested in joining don't hesitate.
The current specs can also be found on the XCD homepage.
After this long introduction let's begin the fun..
You'll need the following software
Mode2 CD Maker
Riff CD/XA filters for playback
Mode2 CD Maker GUI
Step 0: Installation
Unpack Mode2 CD Maker and the GUI to the same directory. Then unpack the playback filter and install it by double clicking on register.bat.
Step 1: Create a mode2 image
Start up the Mode2 CD Maker GUI.
First make sure that the GUI will always find the required applications. Setting the paths of the two programs is actually not necessary
when you put them into the same folder as the GUI but some people always forget to follow step 0.
Then let's get started. First we set a name for the CD and a name for the image file. The image name is actually not of much importance, it's
just a temporary file that you can delete again after burning.
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800 MB CDs 5/23/02 13:59
Then you can also decide where the image should be created. If you want this path to be used make sure you check Path to store CD image
/ files extracted or it won't be used.
After this it's time to select which files you want to be put onto the CD:
This is pretty straightforward. Double clicking on a file will add it to the list of files. There's no size check so you have to make sure that
This is pretty straightforward. Double clicking on a file will add it to the list of files. There's no size check so you have to make sure that
you stay within the allowed limits:
A 650MB CD can contain 738MB, a 700MB one 798MB, an 800MB CD can contain 897MB and a 99 minute CD can contain 987MB, almost 1 GB.
The program will of course show you all the files that are to be added to the image file:
As you can see the files will get another name but that shouldn't bother you too much. As said in the introduction eventually you can use
other names then these predefined ones.
Once you've added all the files you want to put onto the CD press the CD Image build button to create the disc image.
Step 2: Burning the image
Any .cue/.bin capable burning program can be used. Nero, Fireburner, CDRWin and cdrdao are just a few options.
Once burned you should be able to use your favorite media player to open and play the .dat file(s). Normally the players won't open .dat
files by default so you will have to associate the file type to your player of choice.
And a reminder: The riff cd/xa filter is required or the files can't be played.

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