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Technical Considerations



Contact Information:
Toshiba (714)455-0407
Teac (213)726-0303
Sony (800)326-9551

CD-ReWritable (CD-RW)

We've had a lot of questions about CD-ReWritable (CDRW) technology. Therefore we would like to post the following facts:



DVD Basics:

Digital Versatile Discs (DVD's) are the successor to the current CD-ROM technology. DVD-ROM's (a term used to denote a DVD disc reader) operate just like a typical CD-ROM. You may use a DVD-ROM reader instead of, or in addition to a CD-ROM reader. A DVD-ROM reader will read all your normal data CD-ROM and audio CD-ROM media in addition to DVD discs. Most DVD-ROM's can read CD-R media as well. However, some early 1X models could not read CD-R media.

Because DVD-ROM readers use the standard EIDE and SCSI interfaces your operating system will see them just like a CD-ROM reader. They are compatible with all operating systems (yes, Linux too).

DVD Capacity:

DVD discs are the same size as CD-ROM discs but pack much more data, enough data to more than accommodate a full motion picture. Data storage is maximized by utilizing two layers per side for a total of four layers. A single sided, single layered (SS/SL) DVD disc sports 4.7GB's of data, while single sided double layered (SS/DL) DVD disc has a capacity of 8.5GB. Double sided, single layered (DS/SL) discs and double sided, double layered (DS/DL) discs boast 9.4GB and 17GB capacities respectively. A standard diode laser with a 650/635mm wave length is used to read the discs.

Toshiba is developing a "next-generation DVD" product that uses a blue-violet semiconductor laser. These new DVD-ROM's, due out by the year 2000, will sport a 7.5GB capacity per layer. That translates to a 15GB capacity per side. These new DVD-ROM's transfer data at 30Mbps. By the year 2005, Toshiba plans to release a new DVD-ROM with a projected capacity of 50GB's.

DVD Speed:

Don't confuse DVD-ROM speed notation with CD-ROM speed notation. DVD-ROM's currently come in two speeds: 1x (1,350KB/s) and 2x (2,700KB/S). Note that a 1x DVD-ROM reads data at the same rate as a 9X CD-ROM, while a 2X DVD-ROM reads data at the same speed as a 20X CD-ROM.

The DVD consortium:

The DVD standard is controlled by a factious committee called the DVD consortium. The DVD consortium is composed of Matsushita, JVC, Pioneer, Thomson, Hitachi, Mitsubishi, Time Warner, Toshiba, Philips and Sony. Matsushita is a subsidiary of JVC, while Pioneer in turn is a subsidiary of Matsushita. Matsushita, JVC, Pioneer and Thomson tend to stand together opposing standards set by the other members. These four members along with Zenith, compose the NATM retail buying group. The NATM's purchasing power is not lost on the other members. Two other allies, Philips and Sony, tend to stick together on many issues. However, Philips and Sony are currently debating the upcoming DVD audio format (see below).

DVD Audio Obsolete:

DVD-ROM's can play standard audio CD-ROM discs. Newer models due out by the end of 1998 will also be able to play audio DVD discs. CD-ROM discs have a sample frequency of 44.1kHz (See our audio page). DVD audio discs have a sampling frequency of 96kHz. This sounds like the best thing since warm milk! However, if you think about it, most of the music which has been digitally mastered over the last few years has been mastered at 44.1kHz or some multiple of 44.1kHz. In order to re-master these tracks to 96kHz the tracks must be re-sampled producing aliasing artifacts (See our audio page). The result is an audio quality inferior to the original 44.1kHz track. The obvious question is why not just set the DVD audio standard at 88.2kHz, exactly twice 44.1kHz, to preserve current audio tracks without aliasing and continue support for current motion video standards? (44.1kHz was set as the CD audio standard because it synced with existing video formats). This was originally proposed and would have been the best choice. However, Sony wanted credit for the new DVD audio standard so like a 300 pound gorilla, Sony crushed the 88.2kHz standard with its new 96kHz standard. Hence we now have to live with 96kHz. Notwithstanding future audio tracks, mastered natively at 96kHz will be far superior to what we have now on CD-ROM.

Furthermore, to confuse matters, Philips wants to make its stamp on the world too and will introduce a competing 100kHz standard called "Super CD" (yes that CD, even though it's a DVD standard) in 1999.

DVD Audio Update:

Thanks to an anonymous source for this DVD Audio update per

The specification allows for sampling frequencies of 48kHz, 96kHz, and 192kHz, as well as 44.1kHz, 88.2kHz, and 176.4 kHz. Quantization is available in 16 bits, 20 bits and 24 bits, and up to six channels are available for multichannel recording, with a transfer rate of 9.6 Mbps maximum. In addition, the spec supports playback of video clips in the DVD-Video format and "slide shows" can also be viewed while listening to music. Supplemental information, such as liner notes (album title, song titles, artist data, etc.), artist discography, and a URL (Universal Resource Locator) allowing web access are also included.

The format uses lossless compression which will allow 2 channels sampled at 192kHz / 24bit with over 74 minutes of recording time, or 6 channels of 96kHz / 24 bit with 74 minutes of recording time. Of course longer recording times are possible at lower sampling and bit rates.

The discs are not readable in current DVD players or CD players. I’m sure future DVD players will support the DVD-audio discs, but most of the mainstream ones probably won’t support the highest bit rates and sampling rates (and if they do, they would probably be poorly implemented on moderately priced players).

A couple of companies are currently making DVD discs that have 96kHz/24 Bit audio that will work in existing DVD players. The existing DVD-Video format allows for uncompressed 96kHz/24 Bit audio. The companies that make those discs are making them from either very high quality analog master tapes or digital master tapes that were recorded at at least 96kHz / 24 Bit.

Also, a number of people have reported that conventional 44.1kHz / 16Bit or 48kHz / 16 bit audio does sound significantly better when it is converted to a higher sampling rate/bit rate (almost always to an integer multiple of the original sample rate) on a high quality sample rate converter.


You can now buy many motion pictures on DVD discs. DVD motion video is encoded in the MPEG-2 video format. An MPEG-2 decoder PCI card is generally included with a DVD-ROM to play MPEG-2 video on the fly. However, hardware drivers for these cards are proprietary and generally only available for Win95. Many support resolutions up to 1280x1024.

Software decoding may be used instead of a hardware decoding card. However, this requires ample CPU power. A 266MHz Pentium II is suggested as a minimum for software MPEG-2 decoding. A Pentium II 300MHz is probably a better choice for software decoding. A hardware decoding card can be used with slower CPU's because it includes the ARCCOS ASIC vital to decoding MPEG-2. But software solutions will open MPEG-2 DVD video to more operating systems without the need for kludgy hardware decoder drivers.

DVD video is really fun to play with. It's much more than a video. The first thing that struck me about DVD video was that it had alternate audio tracks. While watching a movie one can switch to a variety of foreign languages instead of English. It is a great way to pick up a new language. Commentaries from actors and directors are frequently included. Subtitles may be enabled or disabled. While watching your video you can switch on the fly from widescreen to full-screen format and choose different camera angles. Additional movie trailers a also available.

The DVD-Video specification varies from country to country. Different regions of the world have been assigned different incompatible DVD-ROM discs and readers. The standards are mutually incompatible by design. This is done to prevent U.S. DVD-Video discs, which are frequently released earlier than other in other regions, from being smuggled to other countries that generally won't get their own copy of these films until months later. In the US and Japan DVD-Video will use the NTSC format. In Europe the PAL format will be used.

Originally a variety of audio formats where to be assigned through-out the world as well. However, now it appears that most if not all countries will be allowed to support a single standard for DVD video audio tracks, Dolby Digital AC-3. Dolby Digital AC-3 is a six channel audio format beloing to a larger family known as 5.1. It is very similar to the Digital Theater Systems (DTS) standard. AC-3 will now be used instead of the MPEG-2 audio format. In addition a simple 2-channel linear PCM audio format will also be included.

You have probably heard of Digital Video Express (Divx), the bastard child of DVD video. Divx is a DVD video format invented by Circuit City. While DVD discs may be played an unlimited number of times, Divx discs can only be played for a period lasting two days from the first time you insert the Divx disc into your Divx "enhanced" DVD player. For example, if you buy a Divx on Tuesday and play it for one minute, by Thursday your new Divx disc will become a door stop. I personally will be giving this technology a big fat veto by boycotting all Divx products. I urge DVD manufacturers to not support Divx. The NATM retail buying group comprised of Panasonic, Thomson Pioneer and Zenith will be joining me in my boycott.

DVD Writer formats:

DVD Writers can be used much like we use CD-R's and CD-RW's now. We are currently left with a confusing number of possible standards, each championed by a different set of companies. Currently I know of five formats:

Recording  Media/System Playback-exclusive optical disc Playback-exclusive optical disc Organic DYE Optical Disc Organic DYE  Optical Disc Phase change sytem optical disc
Capacity Single Sided;  Single-layer:4.7GB Dual Layer:8.5GB 650MB Single-Side:3.9GB 
650MB Singe-Side:2.6GB 

DVD links:

DVD-RAM supports the new UDF Filesystem:

Filesystem Universal Disk Format (UDF) file system runs under all of the Windows 95releases (Retail, OSR1 and OSR2) and can support DVD-RAM with a singlepartition (> 2GB). It overcomes the improper handling of large cluster size(e.g. 64K) posed by many Windows accessory programs and the incompatibility of FAT32 among Windows releases. UDF offers the most complete andcompatible solution. In case of DVD-ROM media with capacity larger than 4GB, UDF bears no limitation that exists with FAT 16 and ISO9660,applications are able to take the full advantage of the large mediacapacity. When new generation DVD drives start to rush out and media sizebegins to exceed 4 GB limit, UDF is completely ready for upward compatibility.UDF is designed to be a true cross platform file system, it can be run onall of the major shipping operating systems with both read-writecapabilities. UDF supports Unicode which allows for all the special characters, this is essential for creating multiple language DVD media. UDFalso truly supports long file names. A file name can be up to 255 ASCIIcharacters or 127 Unicode characters. In addition, UDF inherits nolimitation on how many folders can be nested.With UDF, users can easily access a DVD-RAM media in a DVD-ROM drive, itovercomes the problem exists with the FAT file system and the Windows nativeCD device drivers.Unlike other file system that only addresses one type of devices, such asFAT16 for the block addressable devices and ISO9660 for streaming typedevices, UDF was designed to handle both types of devices. This gives themaximum compatibility for storage devices than any other file system.UDF file system is optimized for large contiguous files. In UDF, no matterhow large a file is, it can be managed as one single extent, therefore, it reduces much of the overhead which exists in file systems such as FAT.Further more, since UDF uses the physical block size (2K for DVD-RAM media)as its minimum storage block, it uses a media far more efficiently than FAT.With all the advantages, UDF makes itself the best candidate for the DVDmarket.

Calculating Disk space for audio files

Voice grade recording is done at 8K samples per second in 8 bit (one byte) samples on a single track. This gives you a reasonable reproduction of sound up to around 4kHz. 60Mins of voice grade recording takes up about 1MB:

60minsx(60sec/min)x(8000samples/sec)x(8bits/sample)= 7,680,000 bits
7,680,000 bits x (1KB/1,024bits) = 915KB's

CD audio grade recording is done 44.1K samples per second in 16 bit (two bytes) samples on a two tracks (stereo). This gives you a reasonable reproduction of sounds up to around 20kHz. 60Mins of CD audio grade recording takes up about 600MB's:

60minsx(60sec/minx44,100samples/sec)x(16 bits/sample)x(2channels)= 5,080,320,000 bits
5,080,320,000bitsx(1byte/8bits)x(1MB/1,048,576bytes)= 605MB's

Writing CD-ROM's under Linux

From Net Express:

This version has not been proof-read!

You can use many Windows utilities to write CD-ROM's. Corel and Gear are two of the best Windows Utilities. However, few of these can copy UNIX CD-ROM's. Under Linux you can write UNIX and other CD-ROM's with free software like mkisofs and cdwrite. Indeed, the Linux tools are easier to use if you just want to make an exact copy of a CD-ROM.

Supported CD Writers for Linux



First you must select the files on your hard drive that you want to put on the CD. Then you use mkisofs to create a CD image on your hard drive. Finally you use cdwrite to write the image to the CD-Writer. If you just want to duplicate a CD-ROM you don't need to use mkisofs, instead you can just use the dd command followed by cdwrite. We'll explain this in detail below.


Suggested System Requirements

Writing a CD-ROM is a demanding task. If you can't feed data to the CD-writer fast enough you can get a buffer under-run and the writing process will fail. We suggest you use a good PCI SCSI controller like a BusLogic 948 or 958 or an Adaptec 2940. We also suggest you use a 7200RPM hard drive. Using these components we have never had a buffer under-run. Processor speed and memory are not critical. You can copy a CD directly from an 8X or 12X SCSI CD-ROM reader to a CD-ROM writer to copy a CD. Or you can copy files from your hard disk. For the latter You'll need 680MB's of free hard drive space. Do not use the system at all while your writing the CD-ROM. Writing a full CD will run about 15mins for a 4X Writer or about a half hour for a 2X writer. We first suggest you reboot your machine first and log in as root. Use a canned air to blow dust off the blank CD media first. Also try not to jar the machine while it's writing.


Step I: Making and clearing a partition

We suggest you write the iso9660 file system directly onto a hard drive partition instead of into a file on your file system. To do this type:


Type 'n' for new, then 'p' for primary and pick the next number available for a primary partition (1-4). For example - if this is a new drive just type 1 for the first partition. Start at the next block that's open and then type '+680M'. Then type 'w' for write. (Don't type the quote marks for any of these). Now you have a blank 680MB partition. From here out we'll assume your using /dev/sdb1 (or the first partition of the second SCSI drive) for your iso9660 filesystem. Do not format it! Instead clear it by typing:

dd if=/dev/zero of=/dev/sdb1

/dev/zero is the opposite of /dev/null. It simply writes a bunch of zero's to the partition.


Step II: Making the iso9660 file system

If your merely duplicating a CD-ROM you can simply insert the source CD into your CD-ROM (probably /dev/scd0) and type:

dd if=/dev/scd0 of=/dev/sdb1

That's it! You've created your iso9660 file system and you can skip the section on mkisofs below and go onto the section on cdwrite.

However, if you don't just want to duplicate a cd-rom. Say instead you have a bunch of files on your hard drive you want to transfer to a CD. For this you'll need mkisofs:

mkisofs ver 1.05: mkisofs was written by Eric Youngdale

Def: Generates System Sharing Protocol Records (SSPR) specified by the Rock Ridge Interchange Protocol (RRIP). Using an Orange Book CD-ROM writer you can create Yelloow Book (data), Red Book (audio) or Mixed mode records. It can be used to create iso9660 images with 2048 bytes per track.

from or binaries available from Net Express:

Suggested String:

To copy files from a directory names /src type:

mkisofs -vadDflLRT -o /dev/sdb1 -V Title /src

If these files were copied from a CD-ROM and already have the TRANS.TBL files use:

mkisofs -vadDlLR -o /dev/sdb1 -V Title /src

Notes on mkisofs:

The main mkisofs options are:
-o object device of file neame
-v verbose
-a include ~files & #files (editor backup files for UNIX)
-d omit period at end of names without periods on end
-D allow long dirs
-f Follow Links
-l Allows 32 character file names (not 8.3)
-L Allow periods at beginning of file name
-R make RR & SUSP records (-r is the same but resets UID etc)
-T Create TRANS.TBL for non-Rock Ridge OS's
-x path => Exclude this path (use -x for each path to exclude)
-z experimental transparent compression
-i path/isofs=file where file is a list of files to add

You can add these options to a file called .mkisofs
in your home directory (But you don't need to do this):
APPI = -A Application Identifier
COPY = Copyright
ABST = Abstract(37 char)
BIBL = Bibliography (37 char)
PREP = -p Preparer (128 char)
PUBL = -P Publisher(128 char)
SYSI = System ID (32 char)
VOLI = -V Volume ID (32 char)
VOLS = Volume Set Name (278 char)
# comment lines are ignored

Step III: Writing the CD-ROM

Getting and setting up cdwrite 2.0:

You've written your iso9660 filesystem to /dev/sdb1. Now you use CD Write Ver 2.0.

You can get cdwrite from Net Express: or from or

Before you use it you must create a device called /dev/cdwriter. /dev/cdwriter is just a symbolic link to your CD-ROM writer. You can do this by typing a command like:

ln -s /dev/sgd /dev/cdwriter

'/dev/sgd' is a generic SCSI device. Generic SCSI devices are labeled:

/dev/sga, /dev/sgb, /dev/sgc, /dev/sgd,...etc.

For example, /dev/sgd would be your forth SCSI device. Every SCSI device you have is given a generic SCSI device name in the order they are detected by your controller(s). This is generally the order of the SCSI ID's. Do NOT use /dev/scd0 which is read only!!!

To write a data CD first run:

isosize /dev/sdb1

This will give a size like 149183234

Then run:

cdwrite -ev --hp -b 149183234 /dev/sdb1

Instead of 149183234 put in the result of the isosize /dev/sdb1 command. You may also be able to just run -b `isosize /dev/sdb1` in the same string. Notice those are not single quotes(''). They are back ticks(``). Back ticks are created by the key with the Tilde (~) on it under you ESC key. They are very useful for executing commands within commands.

You can do a test run first by typing:

cdwrite -evy --hp -b 149183234 /dev/sdb1

cdwrite -evy --hp -b `isosize /dev/sdb1` /dev/sdb1

Personally I've abbreviated this all for copying CD's. I write directly from a 15X Toshiba to a Yamaha PC100 via a BusLogic 958. Sine my Toshiba is setup as /dev/scd0, I can just type in:

cdwrite -ev -s 2 -yamaha -b `isosize /dev/scd0` /dev/scd0

But I get tired of typing this so I put it in a file:

echo "cdwrite -ev -s 2 -yamaha -b `isosize /dev/scd0` /dev/scd0" > cpcd
Then I make it executable and put it in my path:
chmod +x cpcd
cp cpcd /usr/bin

Now to copy a CD I just put the source CD in the Toshiba and the destination in the Yamaha, type cpcd and 10 minutes later I have a hot new copy!

To write an Audio CD


cdwrite -ev --hp -s 2 -a track*.cdr

Assuming you have your tracks stored in files called track01.cdr, track02.cdr...

You can copy tracks directly from CD's in digital format with cdda2wav from This works under several different operating systems. Note that I'm talking about copying the audio directly in digital format! Most software uses the DAC built into the CD and converts the audio to analog and writes that back to digital onto you disk. That means every time to you copy you loose a whole generation of quality which is exactly what recording companies want. But if you want the quality of the master you need digital to digital copies. To do this use cdda2wav. Then you can convert it to a cdr file with sox. If your into audio sox is a "must have" for your toolkit. You can download it from

For example to copy tack 8 from a CD in /dev/sgd type:

cdda2wav -q -t8 -d0 -D /dev/sgd name.wav
sox name.wav name.cdr

Better yet be lazy and do it interactively and put this in a script:

# rdtrk writes digital audio CD tracks to disk for 
# pre-mastering an audio CD. From Net Express.
# This program asks the user for a track to read off an
# Audio CD and then writes that track onto the hard disk 
# in CDR format so that it can be written to a CD with 
# cdwrite or played. It is a wrapper for sox. 

echo -ne 'What track number would you like to read? \n' >&2
read TRACK
if [ -z "$TRACK" ]; then
	echo -ne "You did not enter a track: I'm quitting! \n" >&2
	exit 1
echo -ne 'what would you like to name this track?\n' >&2
read NAME
echo -ne "Writing $NAME.cdr, please wait...\n"

(cdda2wav -q -t${TRACK} -d0 -D /dev/sgd ${NAME}.wav; 
sox ${NAME}.wav ${NAME}.cdr ; rm ${NAME}.wav*)
# End of program

Put this in a file called rdtrk and make it executable and put it in your path:

chmod +x rdtrk ; cp rdtrk to /usr/bin/rdtrk

Then just write your CD's with the tracks named in order just as we did before. It's a great way to make a CD of your favorite tunes!

To write a mixed audio and data CD:


cdwrite -ev --hp -b `isosize /dev/sdb1` -d /dev/sdb1 -a track01.cdr

You can ignore the error messages at the end or the write.

Notes on cdwrite:

The main cdwrite options are:
-d data
-a audio
-e eject when done
-v verbose
-D CD Writer: Don't use -D if you:
ln -s /dev/sgd /dev/cdwriter
Do NOT use /dev/scd0 which is read only!!!
If you don't wan to link this add this line:
-D /dev/sgd
-b bytes of source
-y dummy test run
-s 2 2x speed
-P pad
-p Preemptive

That's it! Your done.

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