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Optical Disc FormatsCD and DVD drives can use many types of disc formats and standards. The following sections discuss the formats and file systems used by CD and DVD drives, so you can make sure you can use media recorded in a particular format with your drive. Compact Disc and Drive FormatsAfter 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.licensing.philips.com for more information. Table 13.10 describes the various standard CD formats, which are discussed in more detail in the following sections.
Red Book—CD-DAThe 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-ROMThe Yellow Book was first 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 added additional synchronization and header information to enable sectors to be more accurately located. 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 Inter change on Read-Only 120mm Optical Discs (CD-ROM). The latest version of the Yellow Book is dated May 1999. Green Book—CD-iThe Green Book was published by Philips and Sony in 1986. CD-i is much more than just a disc format; instead it is a complete specification for an entire interactive system consisting of custom hardware (players) designed to be connected to a television, software designed to deliver video and audio together with user interactivity in real time, and the media and format. A CD-i player is actually a dedicated computer usually running a variant on the Motorola 68000 processor line, as well as a customized version of the Microware OS/9 Real Time Operating System. CD-i enables both audio and video to share a disc and enables the information to be interleaved so as to maintain synchronization between the pictures and sounds. To fit both audio and video in the same space originally designed for just audio, compression was performed. The video was compressed using the Moving Picture Experts Group-1 (MPEG-1) compression standard, whereas the audio was compressed with adaptive differential pulse code modulation (ADPCM). ADPCM is an audio encoding algorithm that takes about half the space for the same quality of standard PCM, and even less if quality is reduced by lowering the sampling rate or bits per sample. Using ADPCM, up to 8 hours of stereo or 16 hours of mono sound can fit on one CD. The "differential" part of ADPCM refers to the fact that it records the differences between one signal and the next (using only 4-bit numbers), which reduces the total amount of data involved. ADPCM audio can be interleaved with video in CD-i (and CD-ROM XA) applications. The Yellow Book defines two CD-ROM sector structures, called Mode 1 and Mode 2. The Green Book (CD-i) refines the Mode 2 sector definition by adding two forms, called Mode 2, Form 1 and Mode 2, Form 2. The Mode 2, Form 1 sector definition uses ECC and allows for 2,048 bytes of data storage like the Yellow Book Mode 1 sectors, but it rearranged things slightly to use the 8 formerly unused (blank or 0) bytes as a subheader containing additional information about the sector. The Mode 2, Form 2 definition drops the ECC and allows 2,324 bytes for data. Without the ECC, only video or audio information should be stored in Form 2 sectors because that type of information can tolerate minor errors. All types of media were produced for CD-i, but because the files use the OS/9 file format, they can't be viewed by a PC without special drivers. One of the best resources for CD-i technical information, utility software, drivers, and emulators is The New International CD-I Association Web site at www.icdia.org. Today, the CD-i format is largely obsolete. The last revision of the standard was produced in May 1994. Philips sold off its entire consumer CD-i catalog to Infogrames Multimedia in 1998, which now owns the rights for virtually all consumer CD-i titles ever produced. Philips made a final run of CD-i players in 1999, and it is doubtful any new ones will ever be produced. The legacy of CD-i lives on in the other formats that use specifications originally devised for CD-i, such as the Mode 2, Form 1 and Form 2 sector structures found in CD-XA and the MPEG-1 video format later used in the White Book (CD-Video). CD-ROM XACD-ROM XA originally was defined in 1989 by Philips, Sony, and Microsoft as a supplement to the Yellow Book. CD-ROM XA brings some of the features originally defined in the Green Book (CD-i) to the Yellow Book (CD-ROM) standard, especially for multimedia use. CD-ROM XA adds three main features to the Yellow Book standard. The first consists of the CD-i-enhanced sector definitions (called forms) for the Mode 2 sectors; the second is a capability called interleaving (mixing audio and video information); and the third is ADPCM for compressed audio. The latest version of the CD-ROM XA standard was released in May 1991. InterleavingCD-ROM XA drives can employ a technique known as interleaving. The specification calls for the capability to encode on disc whether the data directly following an identification mark is graphics, sound, or text. Graphics can include standard graphics pictures, animation, or full-motion video. In addition, these blocks can be interleaved, or interspersed, with each other. For example, a frame of video can start a track followed by a segment of audio, which would accompany the video, followed by yet another frame of video. The drive picks up the audio and video sequentially, buffering the information in memory and then sending it along to the PC for synchronization. In short, the data is read off the disc in alternating pieces and then synchronized at playback so that the result is a simultaneous presentation of the data. Without interleaving, the drive would have to read and buffer the entire video track before it could read the audio track and synchronize the two for playback. Sector Modes and FormsMode 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 Tables 13.11 and 13.12.
In the original Yellow Book, Mode 2 was defined as a sector without any ECC or EDC. Unfortunately, Mode 1 (which had ECC and EDC) couldn't be mixed with Mode 2 sectors on the same track (program or song). To enable data with and without error detection and correction in a single track, new sector format subsets for Mode 2 sectors were added in the Green Book (CD-i) and subsequently adopted in the CD-ROM XA extensions. This enabled information that would not tolerate errors (such as programs or computer data) to be interleaved or mixed within the same track with information that would tolerate errors (such as audio or video data). These variations on Mode 2 include Form 1 and Form 2 sectors. Each Mode 2, Form 1 sector is broken down as shown in Tables 13.13, 13.14, 13.15, and 13.16.
Both Mode 2 sector formats add a subheader field that identifies the type of information (such as audio or video) carried in the user data field. The Form 2 sector lacks the ECC of the Form 1 sector and increases the size of the user data field instead. This type of sector is for storing audio or video data that can tolerate errors. Because they don't use any third-level error correction, CD-ROMs that use the Mode 2, Form 2 sector format (such as MPEG video CDs) can hold more user information than other CD-ROM types in the same number of sectors and as a result also have a higher data transfer rate of 174.3KBps instead of the standard 153.6KBps. Note that Form 2 sectors are never used to store data or program files because errors can't be tolerated in that type of information. In that case, the Mode 2, Form 1 sector format would be used. For a drive to be truly XA compatible, the audio data written in Form 2 sectors on the disc as audio must be ADPCM audio—specially compressed and encoded audio. This requires that the drive or the SCSI controller have a signal processor chip that can decompress the audio during the synchronization process. Some earlier drives were called XA-ready, which meant they were capable of Mode 2, Form 1 and Form 2 reading but did not incorporate the ADPCM chip. This is not a significant shortcoming, however, because only certain multimedia titles use the ADPM encoding (with interleaved audio and video). The main benefit XA brought to the table was the additional sector modes and forms taken from the Green Book. Orange BookThe Orange Book defines the standards for recordable CDs and originally 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 (write once read mostly) 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. The 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 times the standard CD speed; the latest version, 2.0, is dated August 1998. Volume 2 (high-speed) defines recording speeds from 4x to 10x 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 OverviewBefore 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:
Disc-at-OnceDisc-at-Once means pretty much what it says: It 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 ever turning off the writing laser; 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. Track-at-OnceMultisession discs can be recorded in either Track-at-Once (TAO) or Packet Writing mode. In Track-at-Once 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 CD-R/RW drive can read the tracks even if the session is not closed, but to read them in a 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 WritingPacket 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 4 sectors for run-in, 2 for run-out, and 1 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 Universal Disk Format (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 drives. One of the most popular packet-writing programs is DirectCD from Roxio. You can even download a universal UDF reader application from Roxio for free that enables you to read UDF 1.5 (packet-written) discs on any CD-ROM or CD-RW drive. When you remove a packet-written disc from the drive, the packet-writing software first asks whether you want the files to be visible to normal CD-ROM drives. If you do then the session must be closed. 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 CD-RW 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 adds even more capability to packet writing and is one of the most important developments in CD and DVD drives. With Mount Rainier, packet writing can become an official part of the operating system 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 CDFirst announced back in 1990 but not available until 1992, Photo CD is a standard for CD-R discs and drives to store photos. The current version 1.0 of the Photo CD standard was published in December 1994. You simply drop off a roll of film at a participating Kodak developer, and they digitize and store the photos on a specially formatted CD-R disc called a Photo CD, which you can then read on virtually any CD-ROM drive connected to a PC running the appropriate software. Originally, Kodak sold Photo CD "players"designed to display the photos to a connected TV, but these have since been dropped in favor of simply using a PC with software to decode and display the photos. Perhaps the main benefit Photo CD has 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 so more photo information could be stored on the disc. Using the Photo CD software, you can view your photographs at any one of several resolutions and manipulate them using standard graphics software packages. When you drop off your roll of film, the Kodak developers produce prints as they normally do. After prints are made, they scan the prints with ultra-high-resolution scanners. To give you an idea of the amount of information each scan carries, one color photograph can take 15MB–20MB of storage. The compressed, stored images are then encoded onto special writable CDs, and the finished product is packaged and shipped back to your local developer for pickup. Some developers can do the scanning on-site. Photo CD Disc TypesThe images on the disc are compressed and stored using Kodak's own PhotoYCC encoding format, which includes up to six resolutions for each image, as shown in Table 13.17. Kodak has defined several types of Photo CDs to accommodate the needs of various types of users. The Photo CD Master disc is the standard consumer format and contains up to 100 photos in all the resolutions shown in the table except for base x64.
The various resolutions supply you with images appropriate for various applications. If, for example, you wanted to include a Photo CD image on a Web page, you would choose a low-resolution image. A professional photographer shooting photos for a print ad would want to use the highest resolution possible. The Pro Photo CD Master disc is intended for professional photographers using larger film formats, such as 70mm, 120mm, or 4''x5''. This type of disc adds an even higher-resolution image (4,096x6,144 pixels) to those already furnished on the Photo CD Master disc. Because of this added high-resolution image, this type of disc can hold anywhere from 25 to 100 images, depending on the film format. The Photo CD Portfolio disc is designed for interactive presentations that include sound and other multimedia content. The high-resolution images that take up the most space are not necessary here, so this type of disc can contain up to 700 images, depending on how much other content is included. Multisession Photo CDsOne breakthrough of the Photo CD concept is that each of the disc types is capable of containing multiple sessions. Because the average consumer wouldn't usually have enough film processed to fill an entire disc, you can bring back your partially filled CDs each time you have more film to develop. A new session can then be added to your existing CD until the entire disc is filled. You pay less for the processing because a new CD is not necessary, and all your images are stored on a smaller number of discs. Any XA-compliant or XA-ready CD-ROM drive can read the multiple sessions on a Photo CD disc, and even if your drive is not multisession capable, it can still read the first session on the disc. If this is the case, you must purchase a new disc for each batch of film you process, but you can still take advantage of Photo CD technology. Kodak provides software that enables you to view the Photo CD images on your PC and licenses a Photo CD import filter to the manufacturers of many desktop publishing, image-editing, and paint programs. Therefore, you can modify your Photo CD images using a program such as Adobe Photoshop and integrate them into documents for printing or electronic publication with a page layout program such as Adobe PageMaker. Picture CDAlthough Kodak still offers Photo CD services, the high cost has led to limited popularity. 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''x6'' and 5''x7'' prints. The images can also be made available via Kodak PhotoNet, where the same images are posted online and can be downloaded. In addition, Kodak has a service called Picture Disk that stores up to 28 images on a 1.44MB floppy disk at a resolution of 400x600, suitable for screensavers and slide shows. 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. Although the image quality of Picture CD isn't as high as with Photo CD, the much lower price of the service should make it far more popular with amateur photographers. 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. White Book—Video CDThe White Book 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 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 video CDs 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 video CDs on virtually any PC with a CD-ROM drive using the free Windows Media Player (other media player applications can be used as well). They also can be played on most DVD players and even some game consoles, such as the Playstation (with the correct options). Video CDs are an especially big hit with people who travel with laptop computers, and the prerecorded discs are much cheaper than DVD—many cost as little as $5. Super Video CDThe Super Video CD specification 1.0, published in May 1999, is an enhanced version of the the White Book Video CD 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 Video CDs or Super Video CDs. Blue Book—CD EXTRAManufacturers 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 CD-ROM 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. A CD-ROM drive in a PC, however, can see both sessions on the disc and access both the audio and data tracks.
Purple BookThe Purple Book defines the standards for double-density CD-ROM (DDCD), CD-R (DDCD-R), and CD-RW (DDCD-RW) media and drives. It was announced by Sony and Philips in July 2000, and the current 1.0 standard was released in July 2001. Purple Book–compliant rewritable drives can read and write standard CD, CD-R, and CD-RW media and achieve their higher 1.3GB (versus 650MB for standard drives) by modifying the following features of existing CD-ROM, CD-R, and CD-RW standards:
DD drives support digital rights management. They are designed to prevent the creation of DD music CDs. Tables 13.18 and 13.19 provide the details of the sector format used by DD drives.
Although DDCD drives have twice the capacity of traditional drives, very few of them were sold. Sony offered several models in 2001 but has since discontinued them, although DDCD media is still available. CD-ROM File SystemsManufacturers of early CD-ROM discs required their own custom software to read the discs. This is because the Yellow Book specification for CD-ROM details only how data sectors—rather than audio sectors—can 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 operating systems. Obviously, noninterchangeable file formats presented an obstacle to the industry-wide compatibility for CD-ROM applications. In 1985–1986, several companies got together and published the High Sierra file format specification, which finally enabled CD-ROMs for PCs to be universally readable. That was the first industry-standard CD-ROM file system that made CD-ROMs universally usable in PCs. Today several file systems are used on CDs, including
Not all CD file system formats can be read by all operating systems. Table 13.20 shows the primary file systems used and which operating systems support them.
High SierraTo make CD-ROM 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 CD-ROM 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 operating system formats. Without this agreement, the maturation of the CD-ROM marketplace would have taken years longer and the production of CD-ROM-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 CD-ROM 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 9660The 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
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 recording files 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 containing CD-ROM tracks. 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 13.10. 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. Figure 13.10. A diagam of basic ISO 9660 file organizational format.
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 operating system, but also tells the computer how it's organized (into directories, which are made up of files). JolietJoliet 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:
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 FormatUDF is a relatively new file system created by the Optical Storage Technology Association (OSTA) as an industry-standard format for use on optical media such as CD-ROM and DVD. UDF has several advantages over the ISO 9660 file system used by standard CD-ROMs but is most noted because it is designed to work with packet writing, a technique for writing small amounts of data to a CD-R/RW 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 DirectCD from Roxio writes in the UDF file system. However, standard CD-ROM drives, drivers, or operating systems such as DOS can't read UDF-formatted discs. Recordable drives can read them, but regular CD-ROM drives must conform to the MultiRead specification (see the section "MultiRead Specifications," later 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 operating systems 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 drives. If you don't have a UDF driver, you can download one for free from Roxio at www.roxio.com. The Roxio UDF Reader is included with DirectCD 3.0 and later. 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. You can close a DirectCD for Windows disc to make it readable in a normal CD-ROM drive, which converts the filenames to Joliet format and causes them to be truncated to 64 characters. You can download the latest (revision 2.01) version of the Universal Disk Format from the OSTA Web site at www.osta.org/specs/index.htm. Macintosh HFSHFS is the file system used by the Macintosh OS. HFS can also be used on CD-ROMs; 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 RidgeThe 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 include 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 RainierMount Rainier is a new standard being promoted by Philips, Sony, Microsoft, and Compaq. Also called EasyWrite (see Figure 13.11), Mount Rainier enables native operating system support for data storage on CD-RW and DVD+RW. This makes the technology much easier to use (no special drivers or packet-writing software is necessary) and enables CD-RW and DVD+RW drives to become fully integrated storage solutions. Figure 13.11. The EasyWrite logo is used on CD-RW and DVD+R/RW drives manufactured in 2003 and beyond that support the Mount Rainier standard.
The main features of Mount Rainier are as follows:
To use Mount Rainier, you must have a drive that supports the standard. These are sometimes called CD-MRW or DVD+MRW drives and might instead bear either the Mount Rainier or EasyWrite logo. Some existing CD-RW drives can be updated to MRW status by reflashing the firmware in the drive; however, most older drives will need to be replaced instead.
See "Updating the Firmware in a CD-RW or Rewritable DVD Drive," p. 793. Also required is software support directly in the operating system (such as with Windows XP or later), or software support can be added via a third-party add-on application for older operating systems. Software Architects (www.softarch.com) produces WriteCD-RW Pro! Software, which enables interchange between Mount Rainier and conventional UDF media, as well as between UDF media written with different programs and to different standards. The first Mount Rainier drive (Philips RWDV1610B) was released in April 2002, and since then many more have followed. Because only minor changes are required in the drive circuitry and firmware to enable Mount Rainier support, many newer drives include Mount Rainier capability; check the drive vendor's Web site or manual to determine compatibility. In addition, the DVD+RW standard was designed with Mount Rainier compatibility in mind—defect management was included inherently from the beginning. (DVD-RW drives don't support defect management, so they are not compatible with Mount Rainier.) The first DVD+RW drives with Mount Rainier/EasyWrite compatibility began shipping in early 2003. Because Mount Rainier essentially makes CD-MRW and DVD+MRW drives function as high-capacity replacements for floppy, Zip, and SuperDisk drives, it won't be long before those are but a distant memory. The latest version of the Mount Rainier specification, version 1.1., includes DVD+RW as well as CD-RW drives. It can be ordered from the Philips Intellectual Property and Standards Web site (www.licensing.philips.com). For more information, go to the Mount Rainier Web site at www.mt-rainier.org. DVD Formats and StandardsAs with the CD standards, the DVD standards are published in reference books produced mainly by the DVD Forum, but also by other companies. The DVD-Video and DVD-ROM standards are pretty well established, but recordable DVD technology is still evolving. The standards situation for recordable DVD is more confusing than usual, especially because there are at least four different (and somewhat incompatible) recording formats! It remains to be seen which will have the best support and become the most popular, but so far the DVD-RW and DVD+RW formats are both very popular. However, DVD+RW looks to be by far the most promising for the future with higher speed, features that make it ideal for both video and data recording, higher compatibility with existing DVD players and drives, and finally Microsoft's endorsement via including support in upcoming versions of Windows. At this point, the only type of recordable DVD I recommend for both home DVD recorders and PC-based DVD recordable drives are units that conform to the DVD+RW format. That also includes DVD±R/RW drives (which support both formats in a single unit), making them essentially compatible with everything. I recommend avoiding drives that do not support the DVD+R/RW format. The current standard DVD formats are shown in Table 13.21.
With advancements coming in blue-light lasers, this capacity will be increased several-fold in the future with an HD-DVD format that can store up to 20GB per layer. Prototype players have already been shown by major manufacturers, although you shouldn't expect to see HD-DVD on the market for several years. DVD drives are fully backward-compatible and as such are capable of playing today's CD-ROMs as well as audio CDs. When playing existing CDs, the performance of current models is equivalent to a 40x or faster CD-ROM drive. Therefore, users who currently own slower CD-ROM drives might want to consider a DVD drive instead of upgrading to a faster CD-ROM drive. Several manufacturers have announced plans to phase out their CD-ROM drive products in favor of DVD. DVD is rapidly making CD-ROMs obsolete in the same way that audio CDs displaced vinyl records in the 1980s. The only thing keeping the CD-ROM format alive is the battle between competing DVD recordable standards and the fact that CD-R and CD-RW are rapidly becoming the de facto replacements for the floppy drive. The current crop of DVD drives features several improvements over the first-generation models of 1997. Those units were expensive, slow, and incompatible with either CD-R or CD-RW media. Many early units asked your overworked video card to try to double as an MPEG decoder to display DVD movies, with mediocre results in speed and image quality. As is often the case with "leading-edge" devices, their deficiencies make them eminently avoidable. Many PC vendors have integrated DVD-ROM drives into their new high-end computers, usually as an option. Originally, most of these installations included an MPEG-2 decoder board for processing the compressed video on DVDs. This offloads the intensive MPEG calculations from the system processor and enables the display of full-screen, full-motion video on a PC. After processors crossed 400MHz in speed, performing MPEG-2 decoding reliably in software became possible, so any systems faster than that usually don't include a hardware decoder card. Some manufacturers of video display adapters have begun to include MPEG decoder hardware on their products. These adapters are known as "DVD MPEG-2 accelerated" and call for some of the MPEG decoding tasks to be performed by software. Any software decoding involved in an MPEG solution places a greater burden on the main system processor and can therefore yield less satisfactory results on slower systems. 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 CompatibilityWhen DVD drives first appeared on the market, they were touted to be fully backward-compatible with CD-ROM 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 or CD-DA players. See the section "MultiRead Specifications," later in this chapter. DVD Movie Playback on a PCAlmost all DVD-ROM and rewritable DVD drives (except for some DVD-RAM drives) include a DVD playback program such as MyDVD or SoftDVD. These programs enable you to interact with a DVD movie the same way you would if it were being played through a DVD player. However, if your video card doesn't have built-in MPEG-2 decoding, you might want to consider upgrading to a better video card that has this feature (all recent ATI and NVIDIA chipsets support MPEG-2 decoding in hardware) or install a separate MPEG-2 decoder. Hardware decoding is very important for best quality, particularly if your processor has a clock speed below 1GHz. If you are using a hardware decoder, it requires an open PCI expansion slot, as well as an interrupt request (IRQ) resource from your system. Also, to view the movies on your PC's display, you must somehow connect the decoder card to your existing video card. This can be accomplished via an internal connection to the card, or it can use a loop-through connection to the monitor port on the back of the card. Some video cards include MPEG-2 decoders (players) built in. Table 13.22 compares MPEG decoder hardware (built in to a separate card or integrated into a video card's 3D accelerator chip) with MPEG player.
DVD Copy ProtectionDVD video discs employ several levels of protection that are mainly controlled by the DVD Copy Control Association (DVD CCA) and a third-party company called Macrovision. This protection typically applies only to DVD-Video discs, not DVD-ROM software. So, for example, copy protection might affect your ability to make backup copies of The Matrix, but it won't affect a DVD encyclopedia or other software application distributed on DVD-ROM discs. Note that every one of these protection systems has been broken, so with a little extra expense or the correct software, you can defeat the protection and make copies of your DVDs either to other digital media (hard drive, DVD+RW, CD-R/RW, and so on) or analog media (such as a VHS or other tape format). A lot of time and money are wasted on these protection schemes, which can't really foil the professional bootleggers willing to spend the time and money to work around them. But they can make it difficult for the average person to legitimately back up his expensive media. The three main protection systems used with DVD-Video discs are:
Regional Playback ControlRegional playback was designed to allow discs sold in specific geographical regions of the world to play only on players sold in those same regions. The idea was to allow a movie to be released at different times in different parts of the world and to prevent people from ordering discs from regions in which the movie had not been released yet. Eight regions are defined in the RPC standard. Discs (and players) usually are identified by a small logo or label showing the region number superimposed on a world globe. Multiregion discs are possible, as are discs that are not region locked. If a disc plays in more than one region, it has more than one number on the globe. The regions are:
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