Upgrading & Repairing PCs: Optical Storage

This chapter is from the book 

Optical Disc Formats

Optical drives can use many types of disc formats and standards. This section discusses the formats and file systems used by optical drives, so you can make sure you can use media recorded in a particular format with your drive.

CD Formats

After Philips and Sony created the Red Book CD-DA format discussed earlier in the chapter, they began work on other format standards that would allow CDs to store computer files, data, and even video and photos. These standards control how the data is formatted so that the drive can read it, and additional file format standards can then control how the software and drivers on your PC can be designed to understand and interpret the data properly. Note that the physical format and storage of data on the disc as defined in the Red Book was adopted by all subsequent CD standards. This refers to the encoding and basic levels of error correction provided by CD-DA discs. The other "books" specify primarily how the 2,352 bytes in each sector are to be handled, what type of data can be stored, how it should be formatted, and more.

All the official CD standard books and related documents can be purchased from Philips for $100—$150 each. See the Philips licensing site at www.ip.philips.com for more information.

Table 11.18 describes the various standard CD formats, which are discussed in more detail in the following sections.

Table 11.18. Compact Disc Formats

Format	Name	Introduced	Notes
Red Book	CD-DA (compact disc digital audio)	1980—by Philips and Sony	The original CD audio standard on which all subsequent CD standards are based.
Yellow Book	CD-ROM (compact disc read-only memory)	1983—by Philips and Sony	Specifies additional ECC and EDC for data in several sector formats, including Mode 1 and Mode 2.
Green Book	CD-i (compact disc-interactive)	1986—by Philips and Sony	Specifies an interactive audio/video standard for non-PC-dedicated player. hardware (now mostly obsolete) and discs used for interactive presentations. Defines Mode 2, Form 1 and Mode 2, Form 2 sector formats along with interleaved MPEG-1 video and ADPCM audio.
CD-ROM XA	CD-ROM XA (extended architecture)	1989—by Philips, Sony, and Microsoft	Combines Yellow Book and CD-i to bring CD-i audio and video capabilities to PCs.
Orange Book	CD-R (recordable) and CD-RW (rewritable)	1989—by Philips and Sony (Part I/II) 1996—by Philips and Sony (Part III)	Defines single-session, multisession, and packet writing on recordable discs. Part I—CD-MO (magneto-optical, with drawn). Part II—CD-R (recordable). Part III—CD-RW (rewritable).
Photo-CD	CD-P	1990—by Philips and Kodak	Combines CD-ROM XA with CD-R multisession capability in a standard for photo storage on CD-R discs.
White Book	VCD	1993—by Philips, JVC, Matsushita, and Sony	Based on CD-i and CD-ROM XA. Stores up to 74 minutes of MPEG-1 video and ADPCM digital audio data.
Blue Book	CD EXTRA (formerly CD-Plus or enhanced music)	1999—by Philips and Sony	Multisession format for stamped discs; used by musical artists to incorporate videos, liner notes, and other information on audio CDs.
Purple Book	CD Double-Density	2000—by Philips and Sony	Double-density (1.3GB) versions of CD-ROM, CD-R, and CD-RW (DD-ROM, DD-R, DD-RW).
Scarlet Book	Super Audio CD	1999—by Philips and Sony	High-capacity (4.7GiB) music disc; hybrid SA-CD discs also feature a CD-DA layer or compatibility with standard players.
DualDisc	DualDisc	2004—by Sony BMG, EMI, Universal Music Group, and Warner Music Group	Double-sided disc; modified CD-DA format for music on one side; flip side is DVD-Video for videos and other content. Slightly thicker than normal CD or DVD media.

Red Book—CD-DA

The Red Book introduced by Philips and Sony in 1980 is the father of all compact-disc specifications because all other "books" or formats are based on the original CD-DA Red Book format. The Red Book specification includes the main parameters, audio specification, disc specification, optical stylus, modulation system, error correction system, and control and display system. The latest revision of the Red Book is dated May 1999.

For more information on the original Red Book format, see the section "CDs: A Brief History," earlier in this chapter.

Yellow Book—CD-ROM

The Yellow Book was published by Philips, Sony, and Microsoft in 1983 and has been revised and amended several times since. The Yellow Book standard took the physical format of the original CD-DA (or Red Book) standard and added another layer of error detection and correction to enable data to be stored reliably. It also provided additional synchronization and header information to enable sectors to be more accurately located. The Yellow Book specifies two types of sectoring—called Mode 1 (with error correction) and Mode 2—which offer different levels of error-detection and -correction schemes. Some data (computer files, for example) can't tolerate errors. However, other data, such as a video image or sound, can tolerate minor errors. By using a mode with less error-correction information, more data can be stored, but with the possibility of uncorrected errors.

In 1989, the Yellow Book was issued as an international standard by the ISO as "ISO/IEC 10149, Data Interchange on Read-Only 120mm Optical Discs (CD-ROM)." The latest version of the Yellow Book is dated May 1999.

Sector Modes and Forms

Mode 1 is the standard Yellow Book CD sector format with ECC and EDC to enable error-free operation. Each Mode 1 sector is broken down as shown in Table 11.19.

Table 11.19. Yellow Book Mode 1 Sector Format Breakdown

Yellow Book (CD-ROM) Sectors (Mode 1):
Q+P parity bytes	784
Subcode bytes	98
Sync bytes	12
Header bytes	4
Data bytes	2,048
EDC bytes	4
Blank (0) bytes	8
ECC bytes	276
Bytes/sector RAW (unencoded)	3,234

Orange Book

The Orange Book defines the standards for recordable CDs and was announced in 1989 by Philips and Sony. The Orange Book comes in three parts. Part I describes a format called CD-MO (magneto-optical), which was to be a rewritable format but was withdrawn before any products really came to market. Part II (1989) describes CD-R, and Part III (1996) describes CD-RW. Note that originally CD-R was referred to as CD-WO (write-once), and CD-RW originally was called CD-E (erasable).

The Orange Book Part II CD-R design is known as a WORM format. After a portion of a CD-R disc is recorded, it can't be overwritten or reused. Recorded CD-R discs are Red Book and Yellow Book compatible, which means they are readable on conventional CD-DA or CD-ROM drives. The CD-R definition in the Orange Book Part II is divided into two volumes. Volume 1 defines recording speeds of 1x, 2x, and 4x the standard CD speed; the last revision, dated December 1998, is 3.1. Volume 2 defines recording speeds up to 48x the standard CD speed. The latest version released, 1.2, is dated April 2002.

Orange Book Part III describes CD-RW. As the name implies, CD-RW enables you to erase and overwrite information in addition to reading and writing. The Orange Book Part III CD-RW definition is broken into three volumes. Volume 1 defines recording speeds of 1x, 2x, and 4x the standard CD speed; the latest version, 2.0, is dated August 1998. Volume 2 (high-speed) defines recording speeds from 4x to 10x the standard CD speed; the latest version, 1.1, is dated June 2001. Volume 3 (ultra-speed) defines recording speeds from 8x to 32x; the latest version, 1.0, is dated September 2002.

Besides the capability to record on CDs, the most important feature instituted in the Orange Book specification is the capability to perform multisession recording.

Multisession Recording Overview

Before the Orange Book specification, CDs had to be written as a single session. A session is defined as a lead-in, followed by one or more tracks of data (or audio), followed by a lead-out. The lead-in takes up 4,500 sectors on the disc (1 minute if measured in time or about 9.2MB worth of data). The lead-in also indicates whether the disc is multisession and what the next writable address on the disc is (if the disc isn't closed). The first lead-out on a disc (or the only one if it is a single session or Disk At Once recording) is 6,750 sectors long (1.5 minutes if measured in time or about 13.8MB worth of data). If the disc is a multisession disc, any subsequent lead-outs are 2,250 sectors long (0.5 minutes in time or about 4.6MB worth of data).

A multisession CD has multiple sessions, with each individual session complete from lead-in to lead-out. The mandatory lead-in and lead-out for each session do waste space on the disc. In fact, 48 sessions would literally use up all of a 74-minute disc even with no data recorded in each session! Therefore, the practical limit for the number of sessions you can record on a disc would be much less than that.

CD-DA and older CD-ROM drives couldn't read more than one session on a disc, so that is the way most pressed CDs are recorded. The Orange Book allows multiple sessions on a single disc. To allow this, the Orange Book defines three main methods or modes of recording:

• Disk At Once (DAO)
• Track At Once (TAO)
• Packet Writing

DAO

DAO is a single-session method of writing CDs in which the lead-in, data tracks, and lead-out are written in a single operation without the writing laser ever turning off; then the disc is closed. A disc is considered closed when the last (or only) lead-in is fully written and the next usable address on the disc is not recorded in that lead-in. In that case, the CD recorder is incapable of writing any further data on the disc. Note that it is not necessary to close a disc to read it in a normal CD-ROM drive, although if you were submitting a disc to a CD-duplicating company for replication, most require that it be closed.

TAO

Multisession discs can be recorded in either TAO or Packet Writing mode. In TAO recording, each track can be individually written (laser turned on and off) within a session, until the session is closed. Closing a session is the act of writing the lead-out for that session, which means no more tracks can be added to that session. If the disc is closed at the same time, no further sessions can be added either.

The tracks recorded in TAO mode are typically divided by gaps of 2 seconds. Each track written has 150 sectors of overhead for run-in, run-out, pre-gap, and linking. A rewritable drive can read the tracks even if the session is not closed, but to read them in a non-rewritable CD-DA or CD-ROM drive, the session must be closed. If you intend to write more sessions to the disc, you can close the session and not close the disc. At that point, you could start another session of recording to add more tracks to the disc. The main thing to remember is that each session must be closed (lead-out written) before another session can be written or before a normal CD-DA or CD-ROM drive can read the tracks in the session.

Packet Writing

Packet writing is a method whereby multiple writes are allowed within a track, thus reducing the overhead and wasted space on a disc. Each packet uses four sectors for run-in, two for run-out, and one for linking. Packets can be of fixed or variable length, but most drives and packet-writing software use a fixed length because dealing with file systems that way is much easier and more efficient.

With packet writing, you use the UDF version 1.5 or later file system, which enables the CD to be treated essentially like a big floppy drive. That is, you can literally drag and drop files to it, use the copy command to copy files onto the disc, and so on. The packet-writing software and UDF file system manage everything. If the disc you are using for packet writing is a CD-R, every time a file is overwritten or deleted, the file seems to disappear, but you don't get the space back on the disc. Instead, the file system simply forgets about the file. If the disc is a CD-RW, the space is indeed reclaimed and the disc won't be full until you literally have more than the limit of active files stored there.

Unfortunately, Windows versions up through Windows XP don't support packet writing or the UDF file system directly, so drivers must be loaded to read packet-written discs, and a packet-writing application must be used to write them. Fortunately, though, these typically are included with CD-RW and DVD rewritable drives The ISOBuster data recovery program reads the contents of damaged CD, DVD, and BD discs and can also be used as a UDF reader.

Windows 7 and Vista support UDF much more thoroughly than previous Windows versions. They are able to format optical media using the Live File System (LFS—Microsoft's term for UDF 2.01), older UDF versions (1.02, 1.5), and the new UDF version 2.5, as well as Mastered. UDF 2.01 discs can be read by Windows XP or later, and they support drag-and-drop file copying on Windows 7 or Vista. UDF version 1.02 is designed for use with DVD-RAM media and is supported by Windows 98 and many Apple computers. UDF version 1.5 works with Windows 2000/XP and Windows Server 2003 as well as Linux systems using kernel version 2.6 or greater. UDF version 2.5 is supported by Windows 7 and Vista. For Linux kernel 2.6.20 and later support of UDF version 2.5, install the UDF-2.50 patch available from http://sourceforge.net.

When you remove a packet-written disc from the drive, the packet-writing software first asks whether you want the files to be visible in all drives. If you do, you must close the session. Even if the session is closed, you can still write more to the disc later, but there is an overhead of wasted space every time you close a session. If you are going to read the disc in a rewritable drive, you don't have to close the session because it will be capable of reading the files even if the session isn't closed.

A newer standard called Mount Rainier (Mt. Rainier) adds even more capability to packet writing. With Mount Rainier, packet writing can become an official part of the operating system (OS) and the drives can support the defect management necessary to make them usable as removable storage in the real world. For more information, see the section "Mount Rainier" later in this chapter.

Photo CD

First announced back in 1990 but not available until 1992, Photo CD was a standard that used CD-R discs and drives to store photos. Although Kodak originally sold Photo CD "players" that were connected to TVs, most Photo CD users used computer-based optical drives along with software to decode and display the photos.

Perhaps the main benefit Photo CD brought to the table is that it was the first CD format to use the Orange Book Part II (CD-R) specification with multisession recordings. Additionally, the data is recorded in CD-ROM XA Mode 2, Form 2 sectors; therefore, more photo information could be stored on the disc.

Kodak's own PhotoYCC encoding format was used to store up to six resolutions for each image, as shown in Table 11.20. The x64 resolution was supported only by the Pro Photo CD master version of the service.

Table 11.20. Photo CD Resolutions

Base	Resolution (Pixels)	Description
/16	128x192	Thumbnail
/4	256x384	Thumbnail
x1	512x768	TV resolution
x4	1,024x1,536	HDTV resolution
x16	2,048x3,072	Print size
x64	4,096x6,144	Pro Photo CD master only

At a time when photo-editing software was in its infancy, the ability to select different sizes optimized for different purposes was quite useful. However, with the rise of high-speed PCs running Adobe Photoshop, Adobe Photoshop Elements, and other photo-editing programs, along with high-speed, low-cost recordable and rewritable optical drives, the Photo CD format became obsolete. Kodak discontinued development in the early twenty-first century, and third-party labs that offered the service discontinued it in 2004. Kodak still offers drivers, software, and firmware for Pro Photo CD at www.kodak.com/global/en/service/professional/products/ekn017045.jhtml.

Picture CD

As a replacement for Photo CD, Kodak now offers the simpler Picture CD service. Unlike Photo CD, Picture CD uses the industry-standard JPEG file format. It uses a CD-R, with up to 40 images stored at a single medium-resolution scan of 1,024x1,536 pixels. This resolution is adequate for 4-inchx6-inch and 5-inchx7-inch prints. The images can also be made available via Kodak Gallery, where the same images are posted online and can be downloaded.

The software provided with Picture CD enables the user to manipulate images with various automatic or semiautomatic operations, but unlike Photo CD, the standard JPEG (JPG) file format used for storage enables any popular image-editing program to work with the images without conversion. Services similar to Picture CD are also offered by Fujifilm and Agfa, and some stores allow you to order Kodak Picture CD with your choice of store-brand or Kodak film processing. You can also create a Picture CD at kiosks that include a Rapid Print Scanner.

White Book—Video CD

The White Book standard was introduced in 1993 by Philips, JVC, Matsushita, and Sony. It is based on the Green Book (CD-i) and CD-ROM XA standards and allows for storing up to 74 minutes of MPEG-1 video and ADPCM digital audio data on a single disc. The latest version (2.0) was released in April 1995. Video CD (VCD) 2.0 supports MPEG-1 compression with a 1.15Mbps bit rate. The screen resolution is 352x240 for NTSC format and 352x288 for European PAL format. In addition, it supports Dolby Pro Logic–compatible stereo sound.

You can think of VCDs as a sort of poor man's DVD format, although the picture and sound quality can actually be quite good—certainly better than VHS or most other videotape formats. You can play VCDs on virtually any PC with an optical drive using the free WMP. (Other media player applications can be used as well.) You can also play VCDs on most DVD players. Although you can create VCDs with popular DVD production programs such as Roxio Creation 2011 or Adobe Premiere Elements, prerecorded VCD media is difficult to find today, thanks to the popularity of the higher-quality (and easier to copy-protect) DVD and Blu-ray formats.

Super Video CD

The Super Video CD specification 1.0, published in May 1999, is an enhanced version of the White Book VCD specification. It uses MPEG-2 compression, an NTSC screen resolution of 480x480, and a PAL screen resolution of 480x576; it also supports MPEG-2 5.1 surround sound and multiple languages.

Most home DVD-creation programs can create VCDs or Super VCDs.

Blue Book—CD EXTRA

Manufacturers of CD-DA media were looking for a standard method to combine both music and data on a single CD. The intention was for a user to be able to play only the audio tracks in a standard audio CD player while remaining unaware of the data track. However, a user with a PC or dedicated combination audio/data player could access both the audio and data tracks on the same disc.

The fundamental problem with nonstandard mixed-mode CDs is that if or when an audio player tries to play the data track, the result is static that could conceivably damage speakers and possibly hearing if the volume level has been turned up. Various manufacturers originally addressed this problem in different ways, resulting in a number of confusing methods for creating these types of discs, some of which still allowed the data tracks to be accidentally "played" on an audio player. In 1995, Philips and Sony developed the CD EXTRA specification, as defined in the Blue Book standard. CDs conforming to this specification usually are referred to as CD EXTRA (formerly called CD Plus or CD Enhanced Music) discs and use the multisession technology defined in the CD-ROM XA standard to separate the audio and data tracks. These are a form of stamped multisession disc. The audio portion of the disc can consist of up to 98 standard Red Book audio tracks, whereas the data track typically is composed of XA Mode 2 sectors and can contain video, song lyrics, still images, or other multimedia content. Such discs can be identified by the CD EXTRA logo, which is the standard CD-DA logo with a plus sign to the right. Often the logo or markings on the disc package are overlooked or somewhat obscure, and you might not know that an audio CD contains this extra data until you play it in a computer-based optical drive.

A CD EXTRA disc normally contains two sessions. Because audio CD players are only single-session capable, they play only the audio session and ignore the additional session containing the data. An optical drive in a PC, however, can see both sessions on the disc and access both the audio and data tracks.

Scarlet Book (SA-CD)

The Scarlet Book defines the official standard for Super Audio CD (SA-CD, also referred to as SACD) media and drives. It was codeveloped by Philips Electronics and Sony in 1999. Unlike the original Red Book CD-Audio standard, which samples music at 44.1KHz, Scarlet Book uses Direct Stream Digital encoding with a sampling rate of 2.822MHz—64 times the sampling frequency of Red Book.

Because of the higher sampling rate and the larger disc capacity necessary to store the audio (as well as SA-CD's support for video and text content), you cannot play standard or dual-layer SA-CD media in a standard CD player or computer's CD or DVD drive. Although standard SA-CD media has a capacity of 4.7GiB (the same as that of single-layer DVD), the formats are not interchangeable. SA-CD contents are copy-protected by a physical watermark known as Pit Signal Processing, which cannot be detected by standard computer DVD drives, although some high-end BD and DVD set-top boxes can also play SA-CD media.

Almost all SA-CD albums use a hybrid dual-layer design, in which the top layer stores standard CD audio playable on standard CD players and drives, and the lower layer contains the higher-density SA-CD content. Essentially, a hybrid SA-CD disc is like a CD-audio disc and a standard SA-CD disc in a single-sided disc (see Figure 11.16).

An SA-CD disc (or the SA-CD layer of a hybrid disc) includes the stereo version of the album in its inner portion, a six-channel surround audio mix in the middle portion, and extra data such as lyrics, graphics, and video in the outer portion.

For listings of SA-CD albums and players and additional SA-CD information, see www.sa-cd.net.

DualDisc

DualDisc, introduced by a consortium of major record labels in the summer of 2004 is a combination of two different formats—music CD and DVD—on a single two-sided disc. DualDisc (sometimes referred to as Dual Disc), as the name suggests, is two discs in one: One side is a music CD, typically featuring support for surround audio or other advanced audio formats, and the other side is a DVD (using the single-layer DVD-5 format) that can include music videos, concert footage, web links, and other features.

Although DualDisc is designed to work in standard CD drives and players, it is not completely compatible with Red Book standards because the CD layer is only 0.9mm, compared to the Red Book standard of 1.1mm. To compensate for spherical aberration caused by a thinner CD layer, one method used is to increase the size of the pits on the CD side of a DualDisc, reducing playing time to 60 minutes. (Some later DualDisc media uses different methods to increase playtime.)

The total thickness of a DualDisc is 1.5mm, compared to 1.2mm for standard CD or DVD media, causing DualDiscs to be incompatible with slot-loading drives in car stereos, PCs, and mega-disc changers. Because DualDisc media is thicker than normal CD media and because the internal structure of the CD side is not compatible with Red Book standards, Philips and Sony (the co-creators of the CD format) do not use the CD logo on DualDisc media, and most DualDisc albums include warning labels that the disc will not work in slot-loaded drives and mega-disc changers and might not play in other types of players. DualDisc albums are typically packaged in CD-style jewel cases.

Although DualDisc media, unlike SA-CD media, supports two standard formats, it is not nearly as popular as SA-CD media. Thousands of albums are available in SA-CD format, but only a few hundred are available in DualDisc format (virtually none after 2006). SA-CD provides far better audio quality than DualDisc (which provides only CD quality music), making it a better format for the serious audiophile.

DVD Formats and Standards

As with the CD standards, the DVD standards are published in reference books produced mainly by the DVD Forum, but also by other companies, such as the DVD+RW Alliance. The DVD Forum's DVD-Video and DVD-ROM standards are well established and are supported by virtually every DVD drive, regardless of age. However, rival recordable and rewritable DVD standards have been developed by both organizations. The DVD Forum developed the following standards:

• DVD-RAM (drag-and-drop file storage and erasure without any add-on software required)
• DVD-R (recordable DVD)
• DVD-RW (rewritable DVD)

After the development of DVD-RAM and DVD-R, the rival DVD+RW Alliance developed these standards:

• DVD+RW (rewritable DVD with support for lossless linking to prevent buffer underrun)
• DVD+R (recordable DVD)

Early rewritable DVD drives supported either DVD-RW or DVD+RW, but recent DVD rewritable drives support DVD+/-R/RW media, and so-called "Super Multi" drives using an LG-designed drive mechanism add support for DVD-RAM media as well. As a result, you can now choose the best DVD media for the task.

DVD rewritable drives support all of these media types.

The current standard and high-capacity DVD formats are shown in Table 11.21.

Table 11.21. Standard and High-Capacity DVD Formats and Capacities

Format	Data Size	Sides	Layers	Data Capacity	MPEG-2 Video Capacity
DVD-ROM Formats and Capacities
DVD-5	120mm	Single	Single	4.7GB	2.2 hours
DVD-9	120mm	Single	Double	8.5GB	4.0 hours
DVD-10	120mm	Double	Single	9.4GB	4.4 hours
DVD-14	120mm	Double	Both	13.2GB	6.3 hours
DVD-18	120mm	Double	Double	17.1GB	8.1 hours
DVD-1	80mm	Single	Single	1.5GB	0.7 hours
DVD-2	80mm	Single	Double	2.7GB	1.3 hours
DVD-3	80mm	Double	Single	2.9GB	1.4 hours
DVD-4	80mm	Double	Double	5.3GB	2.5 hours
Recordable DVD Formats and Capacities
DVD-R 1.0	120mm	Single	Single	3.95GB	1.9 hours
DVD-R 2.0	120mm	Single	Single	4.7GB	2.2 hours
DVD-R DL	120mm	Single	Double	8.5GB	4.0 hours
DVD-RAM 1.0	120mm	Single	Single	2.58GB	N/A
DVD-RAM 1.0	120mm	Double	Single	5.16GB	N/A
DVD-RAM 2.0	120mm	Single	Single	4.7GB	N/A
DVD-RAM 2.0	120mm	Double	Single	9.4GB	N/A
DVD-RAM 2.0	80mm	Single	Single	1.46GB	N/A
DVD-RAM 2.0	80mm	Double	Single	2.65GB	N/A
DVD-RW 2.0	120mm	Single	Single	4.7GB	N/A
DVD+RW 2.0	120mm	Single	Single	4.7GB	2.2hours
DVD+RW 2.0	120mm	Double	Single	9.4GB	4.4 hours
DVD+R 1.0	120mm	Single	Single	4.7GB	2.2 hours
DVD+R DL	120mm	Single	Double	8.5GB	4.0 hours
High-Capacity Optical Formats and Capacities
HD DVD-ROM*	120mm	Single	Single	15GB	4.0 hours HD
HD DVD-ROM[*]	120mm	Single	Double	30GB	8.0 hours HD
HD DVD-R[*]	120mm	Single	Single	15GB	4.0 hours HD
HD DVD-RW[*]	120mm	Single	Single	20GB, 32GB	5.5/8.4 hours HD
BD	120mm	Single	Single	25GB	4.5 hours HD
BD	120mm	Single	Double	50GB	9 hours HD
BD-XL	120mm	Single	Double	100/128GB	18/23 hours
CD-ROM Formats and Capacities (for Comparison)
CD-ROM/R/RW	120mm	Single	Single	0.737GB	N/A
CD-ROM/R/RW	80mm	Single	Single	0.194GB	N/A
HD – HDTV (720p, 1080i, or 1080p resolutions)

DVD drives are fully backward-compatible and as such are capable of reading CDs. When reading or playing existing CDs, the performance of most DVD drives is equivalent to a 40x or faster CD drive. DVD-rewritable drives, which also fully support CD formats, have replaced CD-RW drives at virtually every price point in both new systems and as upgrades at retail. The main reason to use CD media instead of DVD media at this point is for near-universal compatibility (especially when CD-R discs are used) with both older and recent systems.

With the development of BD, rewritable Blu-ray drives that are backward-compatible with DVD and CD media are now available. These drives are much more expensive than rewritable DVD drives; however, the cost of BD drives and media is falling rapidly.

DIVX (Discontinued Standard)

DIVX (Digital Video Express) was a short-lived proprietary DVD format developed by Digital Video Express (a Hollywood law firm) and Circuit City. It was discontinued on June 16, 1999, less than a year after it was released.

The name now lives on as an open encoding standard for DVD video. However, this encoding standard actually has no relation to the original DIVX format other than the name.

DVD Drive Compatibility

When DVD drives appeared on the market, they were touted to be fully backward-compatible with CD drives. Although that might be the case when reading commercially pressed CD-ROM discs, that was not necessarily true when reading CD-R or CD-RW media. Fortunately, the industry has responded with standards that let you know in advance how compatible your DVD drive will be. These standards are called MultiRead for computer-based drives and MultiPlay for consumer standalone devices, such as DVD-Video and CD-DA players. See the section "MultiRead Specifications," earlier in this chapter.

DVD Movie Playback on a PC

DVD video discs (like those included with most of my books) are designed to be played on standard "set-top" DVD players connected to a television. You can also play them on PCs, as long as the proper hardware (for example, a DVD or BD drive) and software are installed. Unfortunately, many people are unaware that the software required to play DVDs is not included by default with most versions of Windows. This means that to play DVDs under Windows, additional software must be installed.

The first versions of Windows to have any sort of built-in DVD-playing capability were Windows 98, 98SE (98 Second Edition), and Me (Millennium edition), all of which included a funky command-line utility called DVDPLAY.EXE. The version of DVDPLAY.EXE included with Windows 98 could only play DVDs if one of two supported hardware DVD decoders were installed, which were physically in the form of a PCI card. The DVDPLAY.EXE application included with Windows Me was the first to support a software decoder (that is, no special card required), as long as the PC had a 333MHz or faster processor. But few people used the DVDPLAY program because most retail PCs and DVD drives sold at the time included commercial DVD-playing software such as WinDVD (Intervideo/Corel) or PowerDVD (Cyberlink). The first version of WMP capable of playing DVDs was WMP 8, which was included with the original release of Windows XP in 2001.

Whereas WMP 8 was included with Windows XP, later WMP versions have been available as free downloads. For example, Windows 98SE, Me, and 2000 support up to WMP 9. (Note that the original Windows 98 release only supports up to WMP 7.1, which is not capable of playing DVDs.) Windows XP and Vista support up to WMP 11, whereas WMP 12 is included with Windows 7.

But just having WMP 8 or later isn't enough. To play DVDs, you must also have a WMP-compatible MPEG-2 decoder installed. An MPEG-2 decoder is included with Windows Vista Ultimate and Home Premium editions, but not with Vista Home Basic and Business editions. Windows 7 Home Premium, Professional, and Ultimate include a decoder, whereas Windows 7 Starter edition does not. No MPEG-2 decoder was included with Windows XP (not even Media Center Edition) or any earlier versions of Windows.

If an MPEG-2 decoder is the missing piece of software needed to play DVDs, where do you get one? Normally you get an MPEG-2 decoder bundled with standalone commercial DVD player programs such as WinDVD and PowerDVD; however, you can also purchase a decoder separately, or even download one for free. To see if you have a DVD decoder currently installed, you can use the Windows XP Video Decoder Checkup Utility (http://tinyurl.com/6xog7).

You can purchase standalone MPEG-2 codecs (coder/decoders) that are compatible with WMP for about $15. Microsoft has a page listing plug-ins for WMP at www.microsoft.com/windows/windowsmedia/player/plugins.aspx.

You can also get MPEG-2 codecs as part of several free "codec packs." My favorite codec packs are the K-Lite Codec Pack (I recommend the Standard or Full versions; http://codecguide.com) and the Vista/Win7 Codec Packages (http://shark007.net).

If you have the proper hardware plus a compatible MPEG-2 decoder installed, you can play DVDs using WMP 8 or later.

Optical Disc File Systems

Manufacturers of early data CDs required their own custom software to read the discs. This is because the Yellow Book specification for CD-ROM detailed only how data sectors—rather than audio sectors—could be stored on a disc and did not cover the file systems or deal with how data should be stored in files and how these should be formatted for use by PCs with different OSs. Obviously, noninterchangeable file formats presented an obstacle to industrywide compatibility for optical disc–based applications.

In 1985–1986, several companies got together and published the High Sierra file format specification, which was the first industry-standard CD-ROM file system that made CD-ROMs universally usable in PCs. Today several file systems are used on optical discs, including the following:

• High Sierra
• ISO 9660 (based on High Sierra)
• Joliet
• UDF (Universal Disk Format)
• Mac HFS (Hierarchical File Format)
• Rock Ridge
• Mount Rainier (also known as Mt. Rainier)

Not all optical disc file system formats can be read by all OSs. Table 11.22 shows the primary file systems used and which OSs support them.

Table 11.22. Optical Disc File System Formats

CD File System	DOS/Win 3.x	Win 9x and Later	Mac OS
High Sierra	Yes	Yes	Yes
ISO 9660	Yes	Yes	Yes
Joliet	Yes1	Yes	Yes[1]
UDF	No	Yes2	Yes[2]
Mac HFS	No	No	Yes
Rock Ridge (RockRidge)	Yes[1]	Yes[1]	Yes[1]
Mount Rainier	No	Yes3	Yes[3]

High Sierra

To make optical discs readable on all systems without having to develop custom file systems and drivers, it was in the best interests of all PC hardware and software manufacturers to resolve the optical file format standardization issue. In 1985, representatives from TMS, DEC, Microsoft, Hitachi, LaserData, Sony, Apple, Philips, 3M, Video Tools, Reference Technology, and Xebec met at what was then called the High Sierra Hotel and Casino in Lake Tahoe, Nevada, to create a common logical format and file structure for CD-ROMs. In 1986, they jointly published this standard as the "Working Paper for Information Processing: Volume and File Structure of CD-ROM Optical Discs for Information Exchange (1986)." This standard was subsequently referred to as the High Sierra format.

This agreement enabled all drives using the appropriate driver (such as MSCDEX.EXE supplied by Microsoft with DOS) to read all High Sierra format discs, opening the way for the mass production and acceptance of CD-ROM software publishing. Adoption of this standard also enabled disc publishers to provide cross-platform support for their software and easily manufacture discs for DOS, UNIX, and other OS formats. Without this agreement, the maturation of the optical marketplace would have taken years longer and the production of optical-based information would have been stifled.

The High Sierra format was submitted to the International Organization for Standardization (ISO). Two years later (in 1988), with several enhancements and changes, it was republished as the ISO 9660 standard. ISO 9660 was not exactly the same as High Sierra, but all drivers that would read High Sierra–formatted discs were quickly updated to handle both ISO 9660 and the original High Sierra format on which it was based.

For example, Microsoft wrote the MSCDEX.EXE (Microsoft CD-ROM extensions) driver in 1988 and licensed it to optical hardware and software vendors to include with their products. It wasn't until 1993 when MS-DOS 6.0 was released that MSCDEX was included with DOS as a standard feature. MSCDEX enables DOS to read ISO 9660–formatted (and High Sierra–formatted) discs. This driver works with the AT Attachment Packet Interface (ATAPI) or Advanced SCSI Programming Interface (ASPI) hardware-level device driver that comes with the drive. Microsoft built ISO 9660 and Joliet file system support directly into Windows 95 and later, with no additional drivers necessary.

ISO 9660

The ISO 9660 standard enabled full cross-compatibility among different computer and operating systems. ISO 9660 was released in 1988 and was based on the work done by the High Sierra group. Although based on High Sierra, ISO 9660 does have some differences and refinements. It has three levels of interchange that dictate the features that can be used to ensure compatibility with different systems.

ISO 9660 Level 1 is the lowest common denominator of all CD file systems and is capable of being read by almost every computer platform, including UNIX and Macintosh. The downside of this file system is that it is very limited with respect to filenames and directories. Level 1 interchange restrictions include the following:

• Only uppercase characters A–Z, numbers 0–9, and the underscore (_) are allowed in filenames.
• Only 8.3 characters maximum for the name.extension (based on DOS limits).
• Directory names are eight characters maximum (no extension allowed).
• Directories are limited to eight levels deep.
• Files must be contiguous.

Level 2 interchange rules have the same limitations as Level 1, except that the filename and extension can be up to 30 characters long (both added together, not including the . separator). Finally, Level 3 interchange rules are the same as Level 2 except that files don't have to be contiguous.

Note that Windows 95 and later versions enable you to use file and folder names up to 255 characters long, which can include spaces as well as lowercase and many other characters not allowed in ISO 9660. To maintain backward compatibility with DOS, Windows 95 and later associate a short 8.3 format filename as an alias for each file that has a longer name. These alias short names are created automatically by Windows and can be viewed in the Properties for each file or by using the DIR command at a command prompt. To create these alias names, Windows truncates the name to six (or fewer) characters followed by a tilde (~) and a number starting with 1 and truncates the extension to three characters. Other numbers are used in the first part if other files that would have the same alias when truncated already exist. For example, the filename This is a.test gets THISIS~1.TES as an alias.

This filename alias creation is independent of your CD drive, but it is important to know that if you create or write to a CD using the ISO 9660 format using Level 1 restrictions, the alias short names are used when files are recorded to the disc, meaning any long filenames will be lost in the process. In fact, even the alias short name will be modified because ISO 9660 Level 1 restrictions don't allow a tilde—that character is converted to an underscore in the names written to the CD.

The ISO 9660 data starts at 2 seconds and 16 sectors into the disc, which is also known as logical sector 16 of track one. For a multisession disc, the ISO 9660 data is present in the first data track of each session. This data identifies the location of the volume area—where the actual data is stored. The system area also lists the directories in this volume as the volume table of contents (VTOC), with pointers or addresses to various named areas, as illustrated in Figure 11.17. A significant difference between the CD directory structure and that of a normal hard disk is that the CD's system area also contains direct addresses of the files within the subdirectories, allowing the CD to seek specific sector locations on the spiral data track. Because the CD data is all on one long spiral track, when speaking of tracks in the context of a CD, we're actually talking about sectors or segments of data along that spiral.

To put the ISO 9660 format in perspective, the disc layout is roughly analogous to that of a floppy disk. A floppy disk has a system track that not only identifies itself as a floppy disk and reveals its density and OS, but tells the computer how it's organized (into directories, which are made up of files).

Joliet

Joliet is an extension of the ISO 9660 standard that Microsoft developed for use with Windows 95 and later. Joliet enables CDs to be recorded using filenames up to 64 characters long, including spaces and other characters from the Unicode international character set. Joliet also preserves an 8.3 alias for those programs that can't use the longer filenames.

In general, Joliet features the following specifications:

• File or directory names can be up to 64 Unicode characters (128 bytes) in length.
• Directory names can have extensions.
• Directories can be deeper than eight levels.
• Multisession recording is inherently supported.

Due to backward-compatibility provisions, systems that don't support the Joliet extensions (such as older DOS systems) should still be capable of reading the disc. However, it will be interpreted as an ISO 9660 format using the short names instead.

Universal Disk Format

UDF is a file system created by the Optical Storage Technology Association (OSTA) as an industry-standard format for use on optical media, but it can also be used by other types of removable-media drives, such as the Iomega REV drives. UDF has several advantages over the older ISO 9660 file system but is most noted because it is designed to work with packet writing, a technique for writing small amounts of data to an optical disc, treating it much like a standard magnetic drive. The UDF file system allows long filenames up to 255 characters per name. There have been several versions of UDF, with most packet-writing software using UDF 1.5 or later. Packet-writing software such as Roxio's DirectCD and Drag-to-Disc, Ahead Software's InCD, and Veritas and Sonic Solutions' DLA use the UDF file system. However, standard optical drives, drivers, and OSs such as DOS can't read UDF-formatted discs. Recordable drives can read them, but regular optical drives must conform to the MultiRead specification (see the section "MultiRead Specifications," earlier in this chapter) to be capable of reading UDF discs.

After you are sure that your drive can read UDF, you must check the OS. Most OSs can't read UDF natively—the support has to be added via a driver. DOS can't read UDF at all; however, with Windows 95 and later, UDF-formatted discs can be read by installing a UDF driver. Typically, such a driver is included with the software that comes with most CD-RW and rewritable DVD drives.

If you don't have a UDF reader, you can download one from the following websites:

• Get UDF Reader 2.5 for Windows XP from http://www.videohelp.com/tools/UDF_Reader
• Get UDF Volume Reader 7.1.0.95 for Windows 9x through XP from http://www.roxio.com/enu/support/udf/software_updates.html
• Get Nero AG Software's InCD Reader from the support section of www.nero.com.

After the UDF driver is installed, you do not need to take any special steps to read a UDF-formatted disc. The driver will be in the background waiting for you to insert a UDF-formatted disc.

If you are unable to read a disc written with UDF on another system, return it to the original system and close the media. This option is usually displayed as part of the Eject Settings dialog box. Closing the disc converts the filenames to Joliet format and causes them to be truncated to 64 characters.

You can download the latest (revision 2.60) version of the Universal Disk Format specification from the OSTA website at www.osta.org/specs/index.htm.

Macintosh HFS

HFS is the file system used by the Macintosh OS. HFS can also be used on optical discs; however, if that is done, they will not be readable on a PC. A hybrid disc can be produced with both Joliet and HFS or ISO 9660 and HFS file systems, and the disc would then be readable on both PCs and Macs. In that case, the system will see only the disc that is compatible, which is ISO 9660 or Joliet in the case of PCs.

Rock Ridge

The Rock Ridge Interchange Protocol (RRIP) was developed by an industry consortium called the Rock Ridge Group. It was officially released in 1994 by the IEEE CD-ROM File System Format Working Group and specifies an extension to the ISO 9660 standard for CD-ROM that enables the recording of additional information to support UNIX/POSIX file system features. Neither DOS nor Windows includes support for the Rock Ridge extensions. However, because it is based on ISO 9660, the files are still readable on a PC and the RRIP extensions are simply ignored.

Mount Rainier

Mount Rainier is a rewritable optical standard developed by Philips, Sony, Microsoft, and HP (Compaq). Also called EasyWrite (see Figure 11.18), Mount Rainier was designed to enable native OS support for data storage on rewritable optical discs.

Mount Rainier's main features include these:

• Integral defect management—Standard drives rely on driver software to manage defects.
• Direct addressing at the 2KB sector level to minimize wasted space—Standard CD-RW media uses a block size of 64KB.
• Background formatting so that new media can be used in seconds after first insertion—Standard CD-RW formatting can take up to 45 minutes depending on drive speed.
• Standardized command set—Standard software cannot work with new drives until revised command files are available.
• Standardized physical layout—Differences in standard UDF software can make reading media written by another program difficult.

Mount Rainier compatibility is also known as CD-MRW or DVD+MRW compatibility. Drives with the Mount Rainier or EasyWrite logo have this compatibility built in, but some existing CD-RW drives can be updated to MRW status by reflashing the firmware in the drive.

You must also have OS or application support to use Mount Rainier. Windows Vista and later have Mount Rainier support built in; Linux kernel version 2.6.2 and above also include Mount Rainier support. For Windows XP or older editions, you must use recent versions of Nero AG Software's InCD or Roxio's DirectCD or Drag-to-Disc or other Mount Rainier–compatible programs to support Mount Rainier.