Scott Muellers Upgrading and Repairing Laptops, Second Edition
| CD 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 Formats
After Philips and Sony had 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 system 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. What the other "books" specify is 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 10.9 describes the various standard CD formats. Table 10.9. Compact Disc Formats
Multisession Recording
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 does 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 Once
Disc 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, and 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 Once
Multisession 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 divided by gaps of normally 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 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 it is much easier and more efficient to deal with file systems that way. With packet writing, you normally 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, which will allow you to read UDF 1.5 (packet-written) discs on any CD-ROM or CD-RW drive.
Note Windows XP also has limited CD-RW support in the form of IMAPI (Image Mastering Application Programming Interface), which allows data to be temporarily stored on the hard drive (staged) before being written to the CD in one session. Additional sessions can be written to the same disc, but there is a 50MB overhead for each session. This gives some of the appearance of packet writing, but it is not really the same thing. To read packet-written discs in the UDF 1.5 or later format, you must install a UDF reader just as with previous versions of Windows. Instead of using IMAPI, I recommend installing a third-party CD-mastering program that also includes packet-writing UDF support, such as Roxio's Easy DVD-CD Creator with DirectCD or Ahead Nero Burning ROM with InCD.
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, 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 the drive will be capable of reading the files even if the session isn't closed. A newer standard called Mount Rainier (or EasyWrite) 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 needed to make them usable as removable storage in the real world. For more information on Mount Rainier, see the section later in this chapter.
Note Microsoft has released updates for Windows XP that add native support for the Mount Rainier standard, which supports full drag-and-drop packet writing through CD-MRW drives as well as DVD+MRW drives.
CD-ROM File Systems
Manufacturers 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 it 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 systems with different operating systems. Obviously, noninterchangeable file formats presented an obstacle to the industrywide 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 to be universally readable. That was the first industry-standard CD-ROM file system that made CD-ROMs universally usable in PCs. This wasn't so much an issue for computer users at the time because the first software on CD-ROM didn't appear until 1987, after the High Sierra format had been published. Most desktop PCs didn't begin incorporating CD-ROM drives until 1987 or later, and the first laptop with an internal CD-ROM drive didn't appear until October 1994. Today, several file systems are used on CDs, including the following:
Not all CD-ROM file system formats can be read by all operating systems. Table 10.10 shows the primary file systems used and which operating systems support them. Table 10.10. CD-ROM File System Formats
[1] A short name, such as (SHORTN~1.TXT), will be shown in place of long filenames. [2] Only if a third-party UDF reader is installed. [3] Requires Mount Rainier (also called EasyWrite) hardware and driver software (Win98 or above) or a third-party reader program.
Note The Mac HFS and Unix Rock Ridge file systems are not supported by PC operating systems such as DOS and Windows and therefore are not covered in depth here.
High Sierra
To 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 “formatted 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, easily manufacturing 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 could read High Sierra “formatted discs were quickly updated to handle both ISO 9660 and the original High Sierra format upon 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 9660
The ISO 9660 standard enabled full cross-compatibility among different computers 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. ISO 9660 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:
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 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-ROM 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 the 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 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 10.10. 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 10.10. A diagram of the 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. Joliet
Joliet is an extension of the ISO 9660 standard, which 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:
Tip Because Joliet supports a shorter path than Windows 9x and newer versions, you might have difficulties mastering a Joliet-format CD that contains extremely long pathnames. I recommend that you shorten the folder names in the file structure you create with the CD-mastering software to avoid problems. Unfortunately, many CD-mastering programs don't warn you about a pathname that is too long until after the burning process starts.
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.
Note A bit of trivia: Chicago was the code name used by Microsoft for Windows 95. Joliet is the town outside of Chicago where Jake was locked up in the movie The Blues Brothers .
Universal Disk Format
The Universal Disk Format (UDF) 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. 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 one of the MultiRead specifications (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. Normally such a driver is included with the software that is included 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, causing them to be truncated to 64 characters. You can download the latest version (revision 2.01) of the Universal Disk Format from the OSTA Web site at www.osta.org/ specs /index.htm. Macintosh HFS
HFS (Hierarchical File System) 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 part of 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 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.
Note Another interesting bit of trivia: The Rock Ridge name was taken from the fictional Western town in the movie Blazing Saddles .
Mount Rainier
Mount Rainier is a new standard being promoted by Philips, Sony, Microsoft, and Compaq. Also called EasyWrite (see Figure 10.11), 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 10.11. 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.
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) for desktop systems was released in April 2002, and since then many more have followed. Mount Rainier drives for laptops are just starting to appear. 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 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. 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 the inclusion of support in upcoming versions of Windows. At this point the only type of recordable DVD I recommend for both home DVD recorders and laptop or desktop PC-based DVD recordable drives are units that conform to the DVD+RW format. Fortunately many manufacturers are now offering dual-mode DVD+-RW drives, which solve the format compatibility problem completely because they are compatible with everything. In the end, dual-mode drives are the best option yet. The current standard DVD formats are shown in Table 10.11. Table 10.11. Standard DVD Formats and Capacities
With advancements coming in blue-light lasers, this capacity will be increased several-fold in the future with a 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. As such, 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 floppy drives. The current crop of DVD drives feature 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 laptop 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 DVD discs. 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 system faster than that usually doesn't include a hardware decoder card. DVD Drive Compatibility
When 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 and CD-DA players. See the section "MultiRead Specifications," later in this chapter. Playing DVD Movies on a Laptop
In order to play DVDs, you need an MPEG-2 decoder. This can take the form of hardware, either custom made or in the form of a PC Card, or software, included in your DVD player application. Almost all modern laptops with DVD-ROM and rewritable DVD drives include a DVD playback program such as WinDVD, MyDVD, or SoftDVD, which includes a software-based MPEG-2 decoder. These programs enable you to play DVD movies the same way you would if it were being played through a set-top DVD player connected to a television. However, if your laptop is slower than 400MHz, it simply won't have enough horsepower to perform the software-based MPEG-2 decoding, and the result will be movies that stutter, drop frames , and in general will be difficult to watch. To rectify this, some of the early DVD-equipped laptops included optional hardware-based MPEG-2 decoders. These decoders could be custom made for a specific laptop model, such as the hardware MPEG-2 decoder IBM offered for its ThinkPad 770 series, or they could be more universal, in the form of a PC Card such as the DVD-to-Go card from Margi Systems. In systems running slower than 400MHz, using a hardware-based decoder was essential if you wanted to successfully play DVD movies. Unfortunately, the hardware-based MPEG-2 decoders for older laptops are generally not available any longer (most have been discontinued) because once they crossed 400MHz in speed, laptops could perform software-based MPEG-2 decoding. Essentially, this means if you install a DVD drive in a laptop that is slower than 400MHz, you may not be able to play DVD movies, unless you can locate a hardware MPEG-2 decoder. DVD Copy Protection
DVD video discs employ several levels of protection, which 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, which means that with a little extra expense or the correct software, the protection can be defeated and you can make copies of your DVDs either to other digital media (hard drive, DVD+RW, CD-R/RW, and so on) or to analog media (such as 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 or her expensive media. Here are the three main protection systems used with DVD-Video discs:
Caution The Digital Millennium Copyright Act (DCMA) signed into law in 1998 prohibits the breaking of copy-protection schemes or the distribution of information (such as tools, Web site links, and so forth) on how to break these schemes.
Regional Playback Control
Regional 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 will have more than one number on the globe. The regions are as follows:
The region code is embedded in the hardware of DVD-Video players. Most players are preset for a specific region and can't be changed. Some companies who sell the players modify them to play discs from all regions; these are called region-free or code-free players. Some newer discs have an added region code enhancement (RCE) function that checks to see whether the player is configured for multiple or all regions and then, if it is, refuses to play. Most newer region-free modified players know how to query the disc first to circumvent this check as well. DVD-ROM drives used in PCs originally did not have RPC in the hardware, placing that responsibility instead on the software used to play DVD-Video discs on the PC. The player software would normally lock the region code to the first disc that was played and then from that point on, play only discs from that region. Reinstalling the software enabled the region code to be reset, and numerous patches were posted on Web sites to enable resetting the region code even without reinstalling the software. Because of the relative ease of defeating the region-coding restrictions with DVD-ROM drives, starting on January 1, 2000, all DVD-ROM drives were required to have RPC-II, which embeds the region coding directly into the drive. RPC-II (or RPC-2) places the region lock in the drive, and not in the playing or MPEG-2 decoding software. You can set the region code in RPC-II drives up to five times total, which basically means you can change it up to four times after the initial setting. Usually, the change can be made using the player software you are using, or you can download region-changing software from the drive manufacturer. Upon making the fourth change (which is the fifth setting), the drive is locked on the last region set. Content Scramble System
The Content Scramble System (CSS) provides the main protection for DVD-Video discs. It wasn't until this protection was implemented that the Motion Picture Association of America (MPAA) would agree to release movies in the DVD format, which is the main reason the rollout of DVD had been significantly delayed. CSS originally was developed by Matsushita (Panasonic) and is used to digitally scramble and encrypt the audio and video data on a DVD-Video disc. Descrambling requires a pair of 40-bit (5-byte) keys (numeric codes). One of the keys is unique to the disc, whereas the other is unique to the video title set (VTS file) being descrambled. The disc and title keys are stored in the lead-in area of the disc in an encrypted form. The CSS scrambling and key writing are carried out during the glass mastering procedure, which is part of the disc-manufacturing process. You can see this encryption in action if you put a DVD disc into the DVD-ROM drive on your PC, copy the files to your hard drive, and then try to view the files. The files are usually called VTS_ xx _ yy .VOB (video object), where the xx represents the title number and the yy represents the section number. Usually, all the files for a given movie have the same title number, and the movie is spread out among several 1GB or smaller files with different section numbers. These VOB files contain both the encrypted video and audio streams for the movie interleaved together. Other files, with an .IFO extension, contain information used by the DVD player to decode the video and audio streams in the VOB files. If you copy the VOB and IFO files onto your hard drive and try to click or play the VOB files directly, you either see and hear scrambled video and audio or receive an error message about playing copy-protected files. This encryption is not a problem if you use a CSS-licensed player (either hardware or software) and play the files directly from the DVD disc. All DVD players, whether they are consumer standalone units or software players on your computer, have their own unique CSS unlock key assigned to them. Every DVD-Video disc has 400 of these 5-byte keys stamped onto the disc in the lead-in area (which is not usually accessible by programs) on the DVD in encrypted form. The decryption routine in the player uses its unique code to retrieve and unencrypt the disc key, which is then used to retrieve and unencrypt the title keys. CSS is essentially a three-level encryption that originally was thought to be very secure, but has proven otherwise . In October 1999, a 16-year-old Norwegian programmer was able to extract the first key from one of the commercial PC-based players, which allowed him to very easily decrypt disc and title keys. A now famous program called DeCSS was then written that can break the CSS protection on any DVD-Video title and save unencrypted VOB files to a hard disk that can be played by any MPEG-2 decoder program. Needless to say, this utility (and others based on it) has been the cause of much concern in the movie industry and has caused many legal battles over the distribution and even links to this code on the Web. Do a search on DeCSS for some interesting legal reading. As if that wasn't enough, in March 2001, two MIT students published an incredibly short (only seven lines long!) and simple program that can unscramble CSS so quickly that a movie can essentially be unscrambled in real-time while it is playing. They wrote and demonstrated the code as part of a two-day seminar they conducted on the controversial Digital Millennium Copyright Act, illustrating how trivial the CSS protection really is. Because of the failure of CSS, the DVD Forum is now actively looking into other means of protection, especially including digital watermarks, which consists essentially of digital noise buried into the data stream, which is supposed to be invisible to normal viewing. Unfortunately, when similar technology was applied to DIVX (the discontinued proprietary DVD standard), these watermarks caused slight impairment of the image ”a raindrop or bullet-hole effect could be seen by some in the picture. Watermarks also might require new equipment to play the discs. Analog Protection System
APS (also called CopyGuard by Macrovision) is an analog protection system developed by Macrovision and is designed to prevent making VCR tapes of DVD-Video discs. APS requires codes to be added to the disc, as well as special modifications in the player. APS starts with the creation or mastering of a DVD, where APS is enabled by setting predefined control codes in the recording. During playback in an APS-enabled (Macrovision-enabled) player, the digital-to-analog converter (DAC) chip inside the player adds the APS signals to the analog output signal being sent to the screen. These additions to the signal are designed so that they are invisible when viewed on a television or monitor but cause copies made on most VCRs to appear distorted . Unfortunately, some TVs or other displays can react to the distortions added to create a less-than -optimum picture. APS uses two signal modifications called automatic gain control and colorstripe. The automatic gain control process consists of pulses placed in the vertical scan interval of the video signal, which TVs can't detect but which cause dim and noisy pictures, loss of color , loss of video, tearing , and so forth on a VCR. This process has been used since 1985 on many prerecorded video tapes to prevent copying. The colorstripe process modifies colorburst information that is also transparent on television displays but produces lines across the picture when recorded on a VCR. Note that many older players don't have the licensed Macrovision circuits and simply ignore the code to turn on the APS signal modifications. Also, various image stabilizer, enhancer , and copyguard decoder units are available that can plug in between the player and VCR to remove the APS copyguard signal and allow a perfect recording to be made. Caring for Optical Media
Some people believe that optical discs and drives are indestructible when compared to their magnetic counterparts. Actually, modern optical drives are far less reliable than modern hard disk drives. Reliability is the bane of any removable media, and CD-ROMs and DVD-ROMs are no exceptions. By far the most common causes of problems with optical discs and drives are scratches, dirt, and other contamination. Small scratches or fingerprints on the bottom of the disc should not affect performance because the laser focuses on a point inside the actual disc, but dirt or deep scratches can interfere with reading a disc. To remedy this type of problem, you can clean the bottom surface of the CD with a soft cloth, but be careful not to scratch the surface in the process. The best technique is to wipe the disc in a radial fashion, using strokes that start from the center of the disc and emanate toward the outer edge. This way, any scratches will be perpendicular to the tracks rather than parallel to them, minimizing the interference they might cause. You can use any type of solution on the cloth to clean the disc, so long as it will not damage plastic. Most window cleaners are excellent at removing fingerprints and other dirt from the disc and don't damage the plastic surface. If your disc has deep scratches, they can often be buffed or polished out. A commercial plastic cleaner such as that sold in auto parts stores for cleaning plastic instrument cluster and tail-lamp lenses is very good for removing these types of scratches. This type of plastic polish or cleaner has a very mild abrasive that polishes scratches out of a plastic surface. Products labeled as cleaners usually are designed for more serious scratches, whereas those labeled as polishes are usually milder and work well as a final buff after using the cleaner. Polishes can be used alone if the surface is not scratched very deeply. The Skip Doctor device made by Digital Innovations (www.skipdoctor.com) can be used to make the polishing job easier. Most people are careful about the bottom of the disc because that is where the laser reads, but the top is actually more fragile! This is because the lacquer coating on top of the disc is very thin, normally only 6 “7 microns (0.24 “0.28 thousandths of an inch). If you write on a disc with a ball point pen, for example, you will press through the lacquer layer and damage the reflective layer underneath, ruining the disc. Also, certain types of markers have solvents that can eat through the lacquer and damage the disc as well. You should write on discs only with felt tip pens that have compatible inks, such as the Sharpie or Staedtler Lumocolor brand, or other markers specifically sold for writing on CDs. In any case, remember that scratches or dents on the top of the disc are more fatal than those on the bottom. Read errors can also occur when dust accumulates on the read lens of your CD-ROM drive. You can try to clean out the drive and lens with a blast of "canned air" or by using a drive cleaner (which can be purchased at most stores that sell audio CDs). If your discs and your drive are clean, but you still can't read a particular disc, your trouble might be due to disc capacity. Many older CD-ROM drives are unreliable when they try to read the outermost tracks of newer discs where the last bits of data are stored. You're more likely to run into this problem with a CD that has lots of data ”including some multimedia titles. If you have this problem, you might be able to solve it with a firmware or driver upgrade for your CD-ROM drive, but the only solution might be to replace the drive.
Sometimes too little data on the disc can be problematic as well. Some older CD-ROM drives use an arbitrary point on the disc's surface to calibrate their read mechanism, and if there happens to be no data at that point on the disc, the drive will have problems calibrating successfully. Fortunately, this problem usually can be corrected by a firmware or driver upgrade for your drive. Many older drives have had problems working under Windows 9x. If you are having problems, contact your drive manufacturer to see whether a firmware or software-driver upgrade is available that might take care of your problem. With new high-speed drives available for well under $100, it might not make sense to spend any time messing with an older drive that is having problems. It might be more cost-effective to upgrade to a new drive (which won't have these problems and will likely be much faster) instead. If you have problems reading a particular brand or type of disk in some drives but not others, you might have a poor drive/media match. Use the media types and brands recommended by the drive vendor. If you are having problems with only one particular disc and not the drive in general, you might find that your difficulties are in fact caused by a defective disc. See whether you can exchange the disc for another to determine whether that is indeed the cause. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||