The compact disc opened up a whole new world of possibilities for the PC. These simple, mass-produced plastic discs could hold up to an hour of stereo music, or as much as 650MB of computer programs and data. Software makers quickly found the CD-ROM to be an outstanding medium for all types of multimedia applications, large databases, and interactive games. But today, the CD-ROM is showing its age, and a single CD no longer provides enough storage for the increasing demands of data-intensive applications (Table 18-1 illustrates the CD technology timeline). A new generation of high-density optical storage called DVD is now appearing for the desktop PC (Fig. 18-1). The acronym DVD stands for several different things. In the early phase of DVD development, it stood for "Digital Video Disc". Later on, it stood for "Digital Versatile Disc" (because it could hold programs and data as well as video and sound). But regardless of what you call it, DVD technology promises to supply up to 17GB of removable storage on your desktop PC. This chapter explores the background and workings of a DVD package, shows you the steps for DVD installation, and offers some basic troubleshooting that can keep you out of trouble.

The argument for DVD is a compelling one because having gigabytes of removable storage to work with opens up some exciting possibilities for entertainment and software development. As DVD works its way into the marketplace, you’re going to see two designations; DVD-Video and DVD-ROM. DVD-Video is the approach used to store movies on the disc (analogous to the way audio is placed on CDs). Eventually, DVD-Video is expected to replace videotape players in home entertainment. DVD-ROM refers to computer-based software and data recorded on the disc. Where audio CDs can be played on CD-ROM drives, DVD-Video discs will be playable on DVD-ROM drives in your PC. Understandably, there are a lot of players looking to make the most of what DVD has to offer:

• Hollywood has been a major factor in the development of DVD-Video - placing full-length movies, sound tracks, and even multi-lingual sub-titling on a single disc. Since all DVD discs are read by laser, there is no physical contact between the disc and its player. The result is that the disc won’t wear out like VHS video tapes.
• Business presentations, education, and professional training will also benefit from DVD technology. Animations, charts, and interactive applets can be integrated with real-time video. This offers a truly immersive training experience that CD-ROM technology has only scratched the surface of.
• Applications for archiving are limitless. Mapping programs, telephone directories, encyclopedias - any software that now spans several CDs can be concentrated on one DVD disc, AND dramatically expanded to offer unprecedented detail.
• Any data-intensive computer software (especially 3D and other interactive games) will get a real boost from the sheer storage volume offered by DVD-ROM.

The next step in exploring DVD is to understand the various specifications "on the box", and becoming familiar with the specifications that make DVD work, and what a DVD will support. You don’t need a lot of technical details, but you should recognize the most important points that you’ll probably run across while reading documentation.

The access time is the time required for the drive to locate the required information on a disc. Optical drives like CD and DVD drives are relatively slow, and can demand up to several hundred milliseconds to access information. For a DVD drive like the Creative Labs (Matsushita) DVD drive, DVD access time is 470ms (almost half a second), while access time for an ordinary CD is 180ms. The reason DVDs require so much more time is because of the greater density of data. However, not all drives are as slow. The Toshiba DVD drive bundled with Diamond Multimedia’s "Maximum DVD Kit" quotes a DVD access time of only 200ms (130ms for CDs).

Once data has been accessed, it must be transferred off of the disc to the system. The data transfer rate measures how fast data can be read from the disc. There are two typical means of measuring the data rate; the speed at which data is read into the drive’s on-board buffer (the "sequential" data transfer rate), and the speed at which data is transferred across the interface to the drive controller (the "buffered" data transfer rate). The Creative Labs (Matsushita) DVD drive offers a sequential data transfer rate of 1.35MB/s, and 900KB/s for an ordinary CD (about equal to a 6X CD-ROM drive). By comparison the drive can support buffered data transfer rates of 8.3MB/s (DMA Mode 2), 13.3MB/s (DMA Mode 1), or 11.1MB/s (PIO Mode 3). As a result, the DVD-ROM drive is compatible with most EIDE drive controllers in the marketplace today.

CD technology is defined by a set of accepted standards - we have come to know these as "books". Since each CD "book" was bound in a different color jacket, each standard is dubbed by color. For example, the standard that defines CD audio is called Red Book. Similarly, DVD technology is defined by a set of "books". There are five books (labeled A through E) which relate to different applications:

• Book A defines the format and approach used for DVD-ROM (programs and data)
• Book B defines DVD-Video
• Book C defines DVD-Audio (this specification is still under development)
• Book D defines DVD-WO (write once)
• Book E defines DVD-E (erasable or re-writeable) and DVD-RAM

All DVD discs must use a data format that describes how data is laid out. Data formats are critical because they outline data structures on the disc such as volumes, files, blocks, sectors, CRCs, paths, records, file allocation tables, partitions, character sets, time stamps, as well as methods for reading and writing. The format use by books A, B, and C is called the UDF Bridge. The UDF bridge is a combination of the UDF (Universal Disk Format created by OSTA - the Optical Storage Technology Association) and the established ISO-9660 format used for CDs. You may see the UDF referred to as standard ISO/IEC 13346. The UDF is a very flexible format that has been adapted to DVD, and made backward-compatible to existing ISO-9660 operating system software (such as Windows 95). Actual utilization of this disk system on DVD discs will depend in large part on what Microsoft dictates as the future operating system standard. Stand-alone DVD movie players are supposed to use UDF, while computer applications will use the UDF Bridge until UDF support becomes universal (possibly as early as Windows 98).

Even with the huge data capacities offered by DVD, an entire movie’s worth of real-time audio and video would never fit on a DVD without some form of compression. Both audio and video must be extensively compressed, and MPEG (Motion Pictures Experts Group) compression has been the scheme of choice. Video compression uses fixed data rate MPEG-1 (ISO/IEC 1117-2) at 30 frames per second with resolutions of 352x240, or variable data rate MPEG-2 (ISO/IEC 13818-2) at 60 frames per second with resolutions of 720x480. Audio compression uses MPEG-1 (ISO/IEC 1117-3) stereo, MPEG-2 (ISO/IEC 13818-3) 5.1 and 7.1 surround sound, or Dolby AC-3 5.1 surround and stereo. MPEG-2 and AC-3 audio compression allow 48 thousand samples per second, where MPEG-1 allows only 44.1 thousand samples per second. MPEG-2 compression is typically regarded as the preferred scheme for DVD.

NOTE: The audio designations "5.1" and "7.1" indicate five (or seven) signal channels, plus one sub-woofer channel.

One of the most important aspects of any technology is "backward compatibility" - how well will the new device support your existing media. The same issue is true for DVD drives. Since DVD technology is designed as an improvement over existing CD-ROMs, the DVD was designed to replace the CD-ROM rather than co-exist with it. Ideally, you’d remove your CD-ROM and replace it with a DVD-ROM drive. This means the DVD must be compatible with as many existing CD-ROM standards as possible. A typical DVD-ROM drive will support CD audio, CD-ROM, CD-I, CD Extra, CD-ROM/XA, and Video CD formats. Multi-session formats such as Photo CD are not yet supported on all DVD drives.

NOTE: One format that is NOT supported by any DVD drive yet is the CD-R (recordable CD) format. The laser used in a DVD cannot read the CD-R, and in some cases, may even damage the CD-R disc. However, new CD-R blanks are being developed which should overcome this problem.

At this point, we can talk about what you need to configure DVD on your desktop, and how each part works. To get a DVD setup running on your computer, you need three things; DVD media, a DVD drive, and an MPEG-2 expansion board.

At its core, DVD technology is identical to classical CD-ROMs - data is recorded in a spiral pattern as a series of pits and lands pressed into a plastic substrate. The actual size and dimensions of a DVD are identical to our current compact discs. However, there are some key differences which give DVD its advantages. First, data is highly concentrated on the disc - where classical CDs use spiral tracks that are 1.6m m apart, DVD tracks are only 0.74m m apart. A typical pit on a classic CD is 0.83m m, but DVD pits are just 0.4m m. Table 18-2 compares the specifications for DVD and CD media. In short, the data on a DVD is much denser than on a regular CD (Fig. 18-2 illustrates the differenced between DVDs and CDs). In order to detect these smaller geometries, the laser used in a DVD operates at a much shorter wavelength (a short-wavelength red laser).

Second, DVD can employ multiple "layers" of pits and lands (each in their own reflective layer), so one physical disk can hold several layers worth of data. The DVD drive’s laser focus control can select which layer to read. Finally, a regular CD only uses one side of the disc, but BOTH sides of the DVD can be used. Combined with this multi-layer technique, the DVD can supply up to four "layers" of data to a DVD drive (Fig. 18-3). In actual practice, DVD-ROM discs will likely only use one side of the disc - at least for a while. What all this means is that a DVD disc can offer up to 8.5GB of storage for a single-sided double-layer disc, or up to 17GB of storage for a double-sided double-layer disc.

As with CDs, a DVD disc is a remarkably reliable long-term storage media (conservative expectations place the life estimates of a DVD disc at about 100 years. However, the longevity of an optical disc is effected by its storage and handling - a faulty CD can cause file and data errors that you might otherwise interpret as a defect in the drive itself. You can get the most life out of your optical disc by obeying the following rules:

• Don't bend the disc. Polycarbonate is a forgiving material, but you risk cracking or snapping (and thus ruining) the disc.
• Don't heat the disk. Remember, the disc is plastic. Leaving it by a heater or on the dashboard of your car will cause melting.
• Don't scratch the disc. Laser wavelengths have a tendency to "look past" minor scratches, but a major scratch can cause problems. Be especially careful of circular scratches (one that follows the spiral track). A circular scratch can easily wipe out entire segments of data which would be unrecoverable.
• Don't use chemicals on the disc. Chemicals containing solvents such as ammonia, benzene, acetone, carbon tetrachloride, or chlorinated cleaning solvents can easily damage the plastic surface.

Eventually, a buildup of excessive dust or fingerprints can interfere with the laser beam enough to cause disc errors. When this happens, the disc can be cleaned easily using a dry, soft, lint-free cloth. Hold the disc from its edges and wipe radially (from hub to edge). Do not wipe in a circular motion. For stubborn stains, moisten the cloth in a bit of fresh isopropyl alcohol (do not use water). Place the cleaned disc in a caddie or jewel case for transport and storage.

NOTE: Contrary to popular belief, DVD discs are not more sensitive to scratches or dust than ordinary CDs.

A DVD drive looks almost identical to a CD-ROM drive in size, shape, and layout. In fact, if not for the "DVD" logo on the tray, you’ll probably mistake a DVD-ROM drive for a CD-ROM drive. The front of a DVD drive (Fig. 18-4) carries all of the standard features that you’d find on any CD-ROM. A motorized disc tray loads and unloads the disc. You can close or open the tray by toggling the Eject button. It’s interesting to note that the Creative Labs DVD-ROM won’t eject a disc that is "locked" by a software application (such as a running movie). You will need to close your DVD application before ejecting the "locked" disc. The Busy indicator lights whenever data is being read from the drive. Since the DVD drive also supports CD audio, you can connect headphones to the headphone jack, and adjust volume right from the front panel.

Much of the rear of a DVD-ROM will also probably look familiar (Fig. 18-5). Power is connected through a 4-pin Molex connector, so you can use any suitable power connector from your power supply. The signal connector is typically either EIDE (40-pin) or SCSI (50-pin), and connects the drive directly to your existing drive adapter. Unlike early CD-ROM drives, DVD-ROM drives do not use "proprietary" drive controllers. A series of small jumpers allows you to set the drive’s identity. For SCSI-type drives, you can set the SCSI ID (usually ID2 through ID6). For EIDE-type drives, you will set the drive as either a primary ("master") or secondary ("slave") drive. If you’re running an EIDE DVD-ROM along with a hard drive, the hard drive would typically be the "master" device, and the DVD-ROM drive would be the "slave" device. If you’re running the DVD-ROM drive alone, set it as the "master" device. Finally, there are two audio output connectors; a 4-pin CD audio connector which attaches to a sound board, and a 2-pin digital audio connector which supplies sound to a digital audio tape (DAT) or other digital recording system.

NOTE: Since DVD drives almost always use EIDE interfaces rather than older IDE interfaces, they may be used along with fast EIDE hard drives on the same EIDE controller channel with no (or negligible) degradation in drive performance.

Things get a little more interesting when you look inside the DVD-ROM drive (Fig. 18-6). Looking in from the top of the drive, you’ll see the major sub-assemblies needed to operate the drive. That black circular wheel near the tray is the spindle motor which turns the disc. You can also see the laser assembly, and the laser sled that the laser rides back and forth on. A small motor drives a screw which runs the sled. The load/unload mechanics run the disc tray in and out (though the mechanical parts are obscured below the plastic tray). The main electronics deck is mounted on the underside of the drive (Fig. 18-7). This is a single printed circuit board which contains all of the circuitry needed to run the drive interface, load/unload motor, audio amplifiers, spindle motor, laser, and laser sled.

One item of particular interest in Fig. 18-7 is the removable IC. This chip contains firmware for the drive, as well as the "region codes" for the drive. Motion picture studios want to control the home release of movies in different countries because theater releases are not simultaneous. Therefore, they have required that the DVD standard include codes which can be used to prevent playback of certain discs in certain geographical regions. Each player is given a code for the region in which it's sold. The player will refuse to play discs which are not allowed in that region. This means that discs bought in one country may not play on players bought in another country. Table 18-3 lists the code numbers, and the regions each number covers. Keep in mind that region codes are entirely optional, and discs without codes will play on any player in any country.

Although the DVD drive requires a SCSI or EIDE drive controller for normal program data, DVD video and audio do not use this data path. There are two reasons for this. First, the data required to reproduce real-time video and audio would bog-down even the fastest PC. Second, video and audio data are highly compressed using MPEG standards, so even of the PC bus wasn’t bogged down by the compressed data, the decompression process would load down the system with processing overhead. In order to play DVD audio and video (DVD-Video), DVD-ROM drives require a stand-alone, hardware-based PCI bus MPEG-2 decoder board such as the one in Fig. 18-8. This MPEG-2 decoder board works independently of the drive controller system, video system, and sound system.

When the original video source is recorded for DVD, MPEG-2 analyzes the video picture for redundant data. In fact, over 95% of the digital data that represents a video signal is "redundant", and can be compressed without visibly harming the picture quality (also referred to as "loss-less compression"). By eliminating redundant data, MPEG-2 achieves excellent video quality at far lower bit rates.

MPEG-2 encoding for DVD is a two-stage process. The original signal is first evaluated for complexity, then higher bit rates are assigned to complex pictures, and lower bit rates are assigned to simple pictures. This allows for an "adaptive" variable bit-rate process. The DVD-Video format uses compressed bit rates with a range of up to 10Mbits/s. Although the "average" bit rate for digital video is often quoted as 3.5Mbits/s, the actual figure will vary according to movie length, picture complexity, and the number of audio channels required. With MPEG-2 compression, a single-layer, single-sided DVD disc has enough capacity to hold 2 hours and 13 minutes of video and audio on a 12cm disc. At the nominal average data rate of 3.5Mbits/s, this still leaves enough capacity for discrete 5.1 channel digital sound in three languages, plus subtitles in four additional languages.

Dolby AC-3 (also called "Dolby Surround AC-3" or "Dolby Digital") is another method of encoding DVD audio besides MPEG-2 audio. With five channels and a common sub-woofer channel (known as "5.1"), you get the effects of 3D surround sound with right, left, center, left ear, right ear, and common sub-woofer speakers. AC-3 runs at 384Kbits/s. In actual practice, DVD products sold in North America and Japan will include Dolby AC-3 sound on the accompanying MPEG-2 board, while DVD products sold in Europe will likely use the MPEG-2 audio standard.

There are five major connections on the MPEG-2 decoder board as shown in Fig 18-9; an Analog Input jack, an Analog Output jack, a Digital Output jack, a Monitor connector, and a Video Input connector. The Analog Input is rarely (if ever) used in normal operations, but it may be handy for mixing-in an auxiliary audio signal to the decoder board. The Analog Output signal provides the master audio signal which is fed to the Line Input of your existing sound board. The advantage of using a Line Input is that you don’t need a volume control on the decoder board. Instead, you can set the Line Input volume through your sound board’s "mixer" applet. When you play a DVD video, any audio will continue to play through your sound board and speakers. The Digital Output is intended to drive an external Dolby Digital device, so you will probably not be using the Digital Output in most basic PC setups.

The MPEG-2 decoder board will now drive your VGA/SVGA monitor through the Monitor connector. This is important because the decoded video stream is converted to RGB information, and fed to the monitor directly - this avoids having to pass the video data across the PCI bus to your video card. The normal output from your video card is looped from your video board to the decoder card, so while the decoder board is idle, your normal video signal is just "passed through" the MPEG-2 board to the monitor.

Even though a DVD package should install with an absolute minimum of muss and fuss, and run with all the reliability of a CD-ROM, there are times when things just don’t go according to plan. Software and hardware problems can both interrupt your DVD system. The following symptoms cover some of the most common troubleshooting issues.

NOTE: DVD drives use lasers in normal operation. Although these are very low-power semiconductor lasers, the chances of injury to your eyes is extremely slight, you should still take the proper precautions and NOT operate a DVD drive with the protective covers open. Turn off and unplug the PC before opening a DVD drive.

Symptom 18-1. The DVD drivers refuse to install. This is almost always because Windows 95 is having a problem with one or more .INF files on your driver installation disk(s). Check with your DVD vendor to confirm whether you need to delete one or more entries in your OEMxx.INF file(s) (where "xx" is any suffix). You may also need to delete one or more entries from a MKEDVD.INF file. The .INF files are typically contained in the C:\WINDOWS\INF\OTHER directory. Once you’ve corrected the appropriate .INF file(s), you can re-install the DVD drivers:

• Click Start, select Settings, then click on Control Panel. Double-click on the System icon.
• Click on the Device Manager tab, then select "Sound, Video, and Game Controllers" or "CD-ROM" as in Fig. 18-10.
• Select the DVD driver(s), then click Remove.
• Exit the Device Manager and reinstall the drivers again.

Symptom 18-2. The DVD drive isn’t detected. There are several possible reasons why the DVD drive would not be detected. Check the power connector attached to the drive, and make sure that the drive isn’t being powered from a "Y splitter" power cable. Check the signal cable next. Both SCSI and EIDE signal cables must be attached securely to the drive. SCSI interfaces are complicated a bit by termination. Make sure that the drive is jumpered properly for its SCSI ID or EIDE "master" or "slave" relationship. Finally, make sure that the DVD drivers are installed and running. Check the drivers under the "Sound, Video, and Game Controllers" (or "CD-ROM" as in Fig. 18-10) entry of your Device Manager.

Symptom 18-3. The DVD motorized tray won’t open or close. The most common issue here is the DVD application itself. Some DVD applications (such as DVD-Video player applications) will "lock" the disc tray closed while a video DVD disc is playing. Try closing all open applications. If the tray still won’t open, try restarting the PC. This should clear any "software lock". If the tray still refuses to open or close, the drive itself may be defective - you can "force" the tray open using a straightened paper clip in the emergency eject hole in the front of the drive.

Symptom 18-4. There is no audio when playing an audio CD. This is a common problem - especially during new DVD-ROM drive installations. Chances are that you did not connect the CD audio cable between the DVD-ROM drive and the sound board. If so, the cable may be reversed (or defective). Of course, if you’re still using your original CD-ROM drive, and the CD-ROM is connected to the sound board, there will be no CD audio from the DVD-ROM drive - there is no way to "parallel" or "gang" the sound cable. If the DVD-ROM audio cable is connected to the sound board, make sure that the "CD-audio" input of your sound board’s mixer applet is turned up to a reasonable level.

Symptom 18-5. There is no DVD audio while playing a movie or other multimedia presentation. Here’s another common oversight during new DVD installations. Check the external audio cable attached between the MPEG-2 decoder board and the Line Input jack of your sound board. The cable may be plugged into the wrong jack(s), or the cable may simply be defective. Also check the sound board’s "mixer" applet and see that the "Line Input" volume control setting is turned up to an acceptable level.

Symptom 18-6. Video quality appears poor. MPEG-2 compression is well-respected for its ability to reproduce high-quality images. The problem with "poor" image quality is almost always because of your video configuration - your color depth or resolution are too low. DVD-Video playback is best at resolutions of 800x600 or higher, and color depths of 16-bits (High Color) or higher (i.e. 24-bit True Color). In most cases, 256 colors will result in a "dithered" image.

Symptom 18-7. The video image is distorted when trying to play an MPEG file. Other video operations probably seem fine. A full or partially-distorted MPEG image can be the result of two problems. First, the video connections on the back of the card could be loose. Verify that all connections to the MPEG-2 decoder card are secure. Another common cause of distorted playbacks is that the refresh rate on your video card is set too high - it is recommended that the video refresh rate be kept below 85Hz when running MPEG files. Try adjusting the vertical refresh rate to 72Hz, or even 60Hz.

Symptom 18-8. The picture is beginning to occasionally pixelize or "break apart". The audio may also seem periodically distorted. It is highly likely that the DVD disc needs to be cleaned. Clean the DVD disc properly and try it again, or try another disc. Also try closing any unused applications running in the background. If the problem persists with another DVD disc as well (and both discs are in good condition), try reinitializing the drive by powering down and rebooting the system. If the problem still persists, the internal optics of the DVD-ROM drive may need to be cleaned with a bit of photography-grade compressed air. Otherwise, try replacing the DVD-ROM drive.

Symptom 18-9. You notice the DVD-ROM light flashing regularly without a disc inserted. System performance may be reduced. This is often because the DVD-ROM drive’s properties are set for "Auto Insert Notification" under Windows 95. Start the Device Manager, highlight the DVD-ROM drive, and click the Properties button. You’ll see the DVD-ROM Properties dialog (Fig. 18-11). In the Options area of the Properties dialog, locate the check box that says "Auto insert notification", and uncheck it. Save your changes (you might need to reboot the system). This should stop the drive’s constant checking for a disc.

Symptom 18-10. You see an error message that says "Disk playback unauthorized". The region code on the DVD disc does not match the code embedded into the drive. There isn’t much that that be done when this error occurs. Note that region code limitations are only applied to DVD-Video movie releases - programs and data discs are generally not marked with region codes.

Symptom 18-11. You see an error indicating the DVD device driver could not be loaded. You’ll need to check the DVD driver installation, or manually install the drivers. To do this, you will need to open the Control Panel, open System Properties, then select the Device Manager tab. In the category of Other Devices, select PCI Multimedia Device and click on Properties. In the Properties dialog, select the Driver tab and click on Change Driver. Browse to the "DVD Drivers Installation Disk" and click on OK. Click on OK again, select the proper MPEG board (such as "MKE DVD-AV Decoder Board"), and click on OK again. Exit the PCI Multimedia Device Properties by clicking on OK again, and Windows 95 will copy over the proper drivers. You will then need to restart the machine.

Symptom 18-12. You see an error such as "Cannot open <filename>, video and audio glitches may occur". This type of error almost always indicated a fault with the driver installation, and you should re-run the "setup" utility which accompanied your the DVD drive product.

Symptom 18-13. The display turns magenta (red) when attempting to adjust the DVD video overlay feature. When adjusting the video overlay, you may have some trouble finding the video window. It often helps to change your background to magenta so you can see where the video window is. To do this, right click on your background, and select Properties. Select the Background tab and select "none" as both the Pattern and the Wallpaper. Then select the Appearance tab and select Magenta, as the color of the desktop. Click on OK to finish changing your background color to magenta. It should now be easier to locate the video window while adjusting the overlay.

Symptom 18-14. The DVD drive cannot read CD-R or PhotoCD discs. This is not an error - most first-generation DVD drives will not read CD recordable or Photo CD (Kodak) disks. In some cases, it is even possible to damage CD recordable disks due to the laser wavelength and energy used in the DVD drive. Do not attempt to read CD-R or Photo CD discs in the DVD unless the drive specifications specifically state that the drive IS compatible with those types of discs.

That concludes Chapter 18. Be sure to review the glossary and chapter questions on the accompanying CD. If you have access to the Internet, take a look at some of the DVD drive manufacturers listed below:

Creative Labs: http://www-nt-ok.creaf.com/mmuk/pcdvd/

Diamond Multimedia: http://www.diamondmm.com

Toshiba: http://www.toshiba.com/taisdpd/dvdrom.htm

Matsushita: http://www.panasonic.com/PCEC/dvd/index-dvd.html