CD-DVD Speed Tutoriall

8/6/2019 CD-DVD Speed Tutoriall

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DVD TutorialDVD, which is once stood for Digital Video Disc and later Digital Versatile Disc, is now just "DVD". It is nolonger an acronym that it once was. DVD is today's premiere format for video, audio, and data storage

The DiscAs a disc, DVD looks very much like the CD. Both are shiny discs that are 4 3/4 inches (12.0 cm) in diameter.Both are optical formats containing digital information. This means a laser pickup is used to read the digitaldata encoded on the disc. But that's where the similarities end.DVD is actually a family ofphysical and application formats. As far as the physical format, DVD can holdanywhere from seven times to over 25 times the digital data on a CD, depending on the the disc'sconstruction. Additionally, the DVD may be used for video, audio, or data storage applications as a DVD-Video, DVD-Audio, or DVD-ROM application format, respectively.

The Physical FormatThere are three reasons for DVD's greater data capacity, smaller pit size, tighter track spacing, and multiplelayer capabilitySmaller Pit Size. DVDs have smaller pit size than CDs. Pits are the slight depressions or dimples on thesurface of the disc that allow the laser pickup to distinguish between the digital 1's and 0's.Tighter Track Spacing. DVDs also feature tighter track spacing (i.e., track pitch) between the spirals of pits.In order for a DVD player to read the smaller pit size and tighter track spacing of the DVD format, a differenttype of laser with a smaller beam of light is required. (This is one of the major reasons why CD playerscannot read DVDs, while DVD players are capable of reading Audio CDs.)Multiple Layer Capability. Finally, DVDs may have up to 4 layers of information, with two layers on eachside. To read information on the second layer (on the same side), the laser focuses deeper into the DVD andreads the pits on the second layer. When the laser switches from one layer to another layer, it is referred toas the "layer switch" or the "RSDL (reverse spiral dual layer) switch". To read information from the other sideof the DVD, almost all DVD players require the user to manually flip the disc.

A comparison of a CD's pit size and track spacing vs. that of a DVD(picture courtesy ofCrutchfield.com)

DVD speed is the maximum speed at which the drive reads data from a DVD disc. The read speed determinesthe data transfer rate. For example a 2X drive provides a 2.7MB/sec maximum transfer rate; a 4.8X driveprovides a 6.536MB/sec rate; and a 5X drive provides a 6.74MB/sec rate.

DVD drive "X" speeds should not be directly compared to CD drive speeds because information on DVDs ismuch more compact than on CDs. Therefore, DVD-ROM drives spin slower, allowing data transfer to be muchfaster. A 2x DVD read speed is roughly equivalent to a 16x rate on a CD.

Two other speeds to consider in a CD/DVD drive are the Access Time and the Transfer Rate. Access Time ismeasured in milliseconds (ms) and indicates the amount of time that elapses from the time a request is madeto the drive until the data begins to be read. Transfer Rate is measured per second and refers to how quicklydata can be read from and sent to the drive. The Transfer Rate is most important when copying a largeamount of data to or from the drive.

What are region codes?Movie studios use region codes on DVDs to thwart unauthorized copying, and to control the release dates ofDVD movies. The actual region code is stored in one byte on the DVD. The DVD player or drive has a regioncode in its firmware. Personal computer DVD-ROM players often have the code in the software or in theMPEG-2 decoder.For the player or drive to play the movie, the two codes must match. The code is also printed on the back ofa DVD package, superimposed on a small image of the globe. If you have a DVD that was made for release inAsia, you won't be able to play it on a DVD player intended for use in Australia.
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Based on DVD's dual-layer and double-sided options, there are four disc constructionformats:1. Single-sided, single-layered3. Single-sided, dual-layered2. Double-sided, single-layered4. Double-sided, dual-layered

1. Single-Sided, Single-Layered. Also known as DVD-5, this simplest construction format holds 4.7 Gigabytes(GBytes) of digital data. The "5" in "DVD-5" signifies the nearly 5 GBytes worth of data capacity. Compared to650 Megabytes (MB) of data on CD, the basic DVD-5 has over seven times the data capacity of that of a CD.That's enough digital information for approximately two hours of digital video and audio for DVD-Video, or 74minutes of high resolution music for DVD-Audio.2. Single-Sided, Dual-Layered. The DVD-9 construction holds about 8.5 GBytes. DVD-9s do not requiremanual flipping: the DVD player automatically switches to the second layer in a fraction of a second, by re-focusing the laser pickup on the deeper second layer. This capability allows for uninterrupted playback oflong movies up to four hours! Frequently, DVD-9 is used to put a movie and its rich set of bonus materials onthe same DVD-Video disc, or its optional DTS Surround Sound track.3. Double-Sided, Single-Layered. Known as DVD-10, this construction features a capacity of 9.4 GBytes ofdata. DVD-10s are commonly used to put a widescreen version of the movie on one side, and a full frameversion of the same movie on the other side. Almost all DVD players require you to manually flip the DVD,

that's why the DVD-10 is called the "flipper" disc. (There are a few DVD players that can perform the sideflipping automatically.)4. Double-Sided, Dual-Layered. The DVD-18 construction can hold approximately 17 GBytes (almost 26 timesthe data capacity of a CD), or about 8 hours of video and audio as a DVD-Video. Think of DVD-18 as a double-sided DVD-9, where up to four hours ofuninterruptedvideo and audio can be stored on one side. To accessthe content on the other side of a DVD-18, you have to manually flip the DVD. To date, few titles have beenreleased using this construction. Content providers (e.g., movie studios) usually choose to go with two DVD-9s than a single DVD-18 because DVD-18s cost far more to produce.

The Application FormatsNow that you understand the various physical aspects and data capacities of the DVD format, let's discuss thevarious application formats of DVD: DVD-Video, DVD-Audio, and DVD-ROM. Each of these three applicationformats are based on the physical specifications we just discussed.

DVD-Video. The DVD-Video format is by far the most widely known, as it is the first DVD application formatto really take off. As the name indicates, DVD-Video is principally a video and audio format used for movies,music concert videos, and other video-based programming. This format first emerged in the spring of 1997and is now considered mainstream, having pass the 10% milestone adoption rate in North America by late2000. Read more about the DVD-Video application format.DVD-Audio. The DVD-Audio format features high-resolution 2-channel stereo and multi-channel (up to 6discrete channels of) audio. The format made its debut much later, in the summer of 2000, due to delay insquaring away the copy protection issue. To date, DVD-Audio titles are still very few in number and have notreach mainstream status, even though DVD-Audio/Video players are numerous and widely available. Readmore about the DVD-Audio application format.DVD-ROM. DVD-ROM is a data storage format just like CD-ROM. DVD-ROMs can only be used in DVD-ROMdrives in computer systems. They allow for data archival and mass storage, as well as interactive and/orweb-based content.

It should be noted that a DVD disc may contain any combination of DVD-Video, DVD-Audio, and/or DVD-ROMapplication content. For example, some DVD movie titles contain DVD-ROM content portion on the same discas the movie. This DVD-ROM content provides additional interactive and web-based content that can beaccessed when using a computer with a DVD-ROM drive. As another example, some DVD-Audio titles areactually DVD-Audio/Video discs that actually have additional DVD-Video content that provide video-basedbonus programming such as artist interviews, music videos, or a Dolby Digital and/or DTS surround soundtrackthat can be played back by any DVD-Video player (in conjunction with a 5.1-channel surround sound hometheater system).Before we leave this general tutorial about the DVD format, let's briefly touch on the topic of recordable DVDformats.
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What About Recordable DVD Formats?As we mentioned before, DVD is actually a family of formats. So far we have only discussedpre-recordedformats, those that have been manufactured with content already recorded (DVD-Video movies and DVD-Audio music recordings). However, DVD also includes recordable formats. In fact, there are three differentrecordable DVD formats:

DVD-R/RW format (with its write-once DVD-R variant and rewriteable DVD-RW variant)

DVD+R/RW format (with its write-once DVD+R variant and rewriteable DVD+RW variant)

DVD-RAM rewritable format

Each of these recordable DVD formats are slightly different. Their differences are enough to create mutuallyincompatibility issues. (That is, one recordable format can not be used interchangeably with the other tworecordable formats.) And not all recordable DVD discs are 100% backwards compatible with the tens ofmillions of existing DVD-Video players and computer DVD-ROM drives

DVD-R/RW Format

The DVD-R/RW format consists of the write-once DVD-R and the rewritable DVD-RW formats. DVD-R/RW is shorthand for DVD-R and DVD-RW DVD-R comes in two flavors: DVD-R Authoring and DVD-R General.

DVD-R for Authoring is for the commercial world, where its primary application is DVD authoring (or contentgeneration).

DVD-R for General, as the name implies, is for consumer and home use. When you buy a DVD-R disc, be sureto buy the DVD-R General format. DVD-R for Authoring discs will not work, as they are designed for DVD-RAuthoring devices which employ slightly shorter 625-nm wavelength lasers. Early DVD-R discs have twocapacities, 3.95 GB or 4.7 GB. Nowadays, all DVD-R discs are made with 4.7 GB capacity.Recording works on the principle of a red laser permanently transforming a dye-recording layer on the DVD-Rdisc, similar to how CD-R recording (or burning) works. This permanent transformation of the media ischaracteristic of a write-once format. DVD-R has an expected lifespan of about 100 years. Like the DVD-Videoformat, the video information is written as a single track, starting from the inner-most portion of the disc andspiraling out to the outer edge. (We bet you didn't know that.) Since it achieves a reported better than 90%backwards compatibility with existing DVD-Video players and computer DVD-ROM drives, DVD-R is ideal forarchiving and distributing home videos. Theres a high likelihood that the DVD-R you make would be viewableon any DVD-Video player and computer DVD-ROM drive, but there is no 100% guarantee - it is not possible intodays world of recordable DVD formats.Introduced in late 1999, DVD-RW supports 1,000 rewrite cycles with a 4.7 GB data capacity. It uses phase-change technology, allowing video and data to be recorded incrementally as a series of sequential recordingsessions. The format also allows for a single start-to-finish disc-at-once recording session, when the disc isfinalized at the end. Finalization is a process that essentially "completes" the recording process and makes thedisc readable by playback-only devices. DVD-RW has a backwards compatibility rate of roughly 65% withexisting DVD-Video players and DVD-ROM drives. Its expected shelf life is at least 30 years.

DVD+R/RW Format

The DVD+R/RW format consists of the write-once DVD+R and the rewritable DVD+RW variants. DVD+RW officially stands for DVD+ReWritable Video. Note the previous format had a dash (-), while this format has aplus (+). In comparison with the

other formats, the DVD+R/RW format was last to be introduced.The rewritable DVD+RW variant was introduced in late 2001, before its write-once variant was even conceived.The write-once DVD+R variant was later announced by Philips at the 2002 Consumer Electronics Show forintroduction in mid-2002. DVD+R/RW competes directly with the DVD-R/RW format. Interestingly, DVD+R andDVD+RW formats are not endorsed by the DVD Forum, nevertheless, the following manufacturers havecommitted to this format: Sony (who also supports the DVD-R/RW format), Yamaha, Thomson, Ricoh,Mitsubishi Chemical, Hewlett-Packard, Dell, and Microsoft. Microsoft joined the DVD+RW Alliance late, in May2003.So what does the DVD+R/RW format have going for it? Well, technically the DVD+R variant allows editing to beperformed until the disc is finalized. And finalizing a DVD+R disc takes about one minute, versus about 15minutes for a DVD-R disc. Philips claims that DVD+R/RW is backwards compatible with mostexisting DVD-Video players and computer DVD-ROM drives. Realistically, expect about 85% backwards compatibility forDVD+R and about 65% backwards compatibility for DVD+RW.
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DVD+R holds 4.7 GB for a single-sided disc, or 9.4 GB for a double-sided disc. Video can be recorded in HighQuality (HQ) or standard play (SP) recording mode for up to 500 lines of resolution, or in Long Play (LP) orextended play (EP) recording mode for up to 250 lines of resolution. The DVD+R/RW formats use losslesslinking to maximize recording time. This works by minimizing the large blank spots caused by multiplerecording sessions. Like DVD-R, DVD+R uses a red laser to permanently transform a dye-recording layer onthe DVD+R disc for write-once recording. DVD+R has an expected lifespan of about 30-100 years and eachblank disc costs about $4 as of May 2003.DVD+RW uses phase-change technology for multiple re-rewrites, up to 1,000 cycles. It boasts a defect

management feature and short formatting time. DVD+R/RW writes data from the inside edge spiraling out theouter edge, just like a DVD-Video disc. The format supports recording in both constant angular velocity (CAV)(constant rotation speed) and constant linear velocity (CLV) (constant linear track speed, with disc rotation fasterwhen the track being written to/read from is closer to the inner hub) modes. You should always use the CLVmode, since CAV recordings cannot be read by DVD-Video players and computer DVD-ROM drives

DVD-RAM FormatThe third recordable DVD format is DVD-RAM. It was invented by Matsushita, the parent company ofPanasonic and Technics, and was introduced in summer of 1998. The DVD-RAM format is supported by theDVD Forum. A DVD-RAM disc looks like any other DVD, and the name DVD-RAM incorporates the lettersDVD. But make no mistake, DVD-RAM is in many ways not a real DVD. As the second part of its nameclearly states, it is like random access memory (RAM). The easiest way to explain the DVD-RAM format is tothink of it as a removable hard disk. DVD-RAM uses phase change dual and magneto-optic technologies for up

to 100,000 recording cycles.A single-sided 12-cm (4.75-inch) DVD-RAM disc holds 4.7 GB, so a double-sided 12-cm DVD-RAM disc holds9.4 GB. DVD-RAM discs also comes in a compact size of 8-cm (3-inch). This smaller version is used in DVD-RAM camcorders from Hitachi and Panasonic. A double sided 8-cm DVD-RAM disc has a capacity of 2.8 GB,enough for 60 minutes of high resolution video. The early version of the DVD-RAM format required a disccartridge (or caddy), while later models may or may not use the cartridge design. The current design allows thedisc to be removed from the cartridge housing. DVD-RAM is expected to have a lifespan of about 30 years.

DVD-RAMs principal advantages are its removable hard disk characteristic and robustness, making it ideal forcomputer data storage. Data storage is random and non-linear, meaning data can be stored in non-contiguousblocks, much like a computer hard disk. In a video editing application, as you perform cut and insert videoediting functions with a DVD-RAM recorder, the video streams can be dynamically linked in the new order thattheyre edited, without having to re-record video streams on the disc in physical sequential order. This is the

random access feature of DVD-RAM. Additionally, DVD-RAM incorporates a defect management feature toensure that the video stream is recorded in a non-defective area of the disc, so content loss is minimized.Inherent in its design, a DVD-RAM disc is incompatible with virtually all DVD players and computer DVD-ROMdrives. Only DVD-Video players made by Panasonic since 2001 are playback-compatible with DVD-RAMdiscs. Such players are designated by Panasonic as DVD-RAM compatible. The backwards incompatibilityissue puts the DVD-RAM format at a huge disadvantage when it comes to sharing home videos and otherrecordings with family and friends.

So which is the best recordable DVD format?Well that really depends too... You didnt think it would be that easy, did you?For a standalone DVD recorder, we think the DVD-R/RW is the best format.Here is why. The ability to share a recordable DVD disc with families and friends (and their ability to play it backon their DVD-Video player or computer DVD-ROM drive) is important. Therefore, backwards compatibility withexisting DVD-Video players and computer DVD-ROM drives is essential. The write-once DVD-R formatreportedly offers a better than 90% backwards compatibility rate. If this is true, it is clearly the best format forsharing your home video collection. In comparison, DVD+R runs a close second, with an expected backwardscompatibility rate of about 85%. DVD-RAM is a non-starter, with its radically different design optimized forcomputer data storage.

Two separate formats are competing for the recordable DVD market: DVD-R/DVD-RW and DVD+RW. DVD-Rallows write once DVD burning at a speed of 2x, rewritable media is limited to 1x. DVD+RW, however, featuresrewritable burning at 2.4x. DVD speeds are rated differently than CD drives; 2x on a DVD writer is equivalent tothe speed of data a 16x CD writer can burn at.


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Here are relative strengths of DVD+RW over DVD-RW:

Record performance. DVD-RW drives are currently limited to 1x record speed (10 megabits/second),whereas DVD+RW drives can write at 2.4x speed (about 25 megabits/second). Note, however, that youcan get DVD-R (write once) disks that can record at 2x speeds.

DVD+RW supports defect management; DVD-RW does not. DVD+RW drives support both CLV (constant linear velocity) and CAV (constant angular velocity) spin

rates. The second is particularly important for PC users, as it allows for higher speed DVD and CD-ROMreading.

DVD+RW has been adopted by Microsoft to natively support the Mount Rainier standard for drag-and-drop, rewritable optical storage.

DVD+RW supports high-accuracy editing of 32K blocks in place, called "lossless sector linking" DVD+RW supports variable bit-rate encoding for video, resulting in better image quality in high-motion

scenes. There's no lead-on or lead-out times needed during write There's no "finalize" state to creating a DVD video disc, unlike DVD-RW.

And here are some advantages of DVD-RW over DVD+RW: Despite the goal of universal compatibility, more consumer DVD players to date will read DVD-RW disks

than DVD+RW disks "out of the box". If allowed to set the compatibility bit (as in the HP drive wereview), that number goes up. Note that newer consumer drives can read both formats.

Most mastering houses that will press consumer DVDs are set up to accept DVD-R media; some will

accept DVD-RW as well. There's currently greater penetration and awareness of DVD-RW among authoring professionals.

Although aftermarket DVD+RW solutions exist for the Macintosh, the Macintosh can natively read andwrite DVD-RW.

The good news is that there will be a single standard for next generation, high capacity recordable opticalmedia, known as "Blu-Ray". Those drives will probably arrive in 2004, use a blue laser and offer 30GBcapacities. Until then, our best advice is to wait for the second generation drives that offer full DVD+R support, ifyou feel you need lower cost, write-once media. These should be hitting the streets in May.

What does the x stand for on 32x?The x on 32x means that theoretically this drive is 32 times faster then the original CD-ROM drive. See ourtransfer rates for exact speeds.

DRIVE SPEED TRANSFER RATE (BPS) ACCESS TIME (ms)

Single-speed (1x) 153,600 400

Double-speed (2x) 307,200 300

Triple-speed (3x) 460,800 200

Quad-speed (4x) 614,400 150

Six-speed (6x) 921,600 150

Eight-speed (8x) 1,228,800 100

Ten-speed (10x) 1,536,000 100

Twelve-speed (12x) 1,843,200 100

Sixteen-speed (16x) 2,457,600 90

Eighteen-speed (18x) 2,764,800 90

Twenty-four-speed (24x) 3,686,400 90

Thirty-two-speed (32x) 4,915,200 85

One-hundred-speed (100x) 15,360,000 80

CAV drives (12x - 24x) 1,843,200 - 3,686,400 150-90

When referring to a computer CD drive, an "x" refers to the transfer speed. For example the original 1X CD-ROM had a speed of 153,600 BPS, this means a 24X has a BPS of 3,686,400 or 153,600 x 24. The higher thenumber the faster data is going to be read from the CD drive.


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There are three different types: CLV,CAV and P-CAV.First it's important to know that, unlike hard disks, the data density on a CD is the same on every part of thedisc. This means that there is more data on the outer part of the disc then on the inside.

CLV (Constant Linear Velocity)The data transfer rate is kept at a fixed level by changing the rotation speed.This means you should get the number that's displayed on the box.

CAV (Constant Angular Velocity)The drive maintains a consistent rotation speed which will result in a variable transfer rate.If you're buying a new CD-Rom unit, it's very likely that you will only see the maximum speed the drive canachieve.To know what the real speed is, you have to look in the manual or on the website from the manufacturer. Thereyou will see two speeds: the minimum and the maximum.The average transfer rate is (min+max)/2.

P-CAV (Partial Constant Angular Velocity)This is a combination of CLV and CAV.The transfer rate goes up until the drive reaches it's maximum speed (CAV). From that point the drive will slowdown and the transfer rate will be constant (CLV).

Because P-CAV drives reach their maximum speed much sooner than CAV drives, the average transfer rateshould be higher

CD-ROM drives which are over 16x will generally have max written next to it. When max is written next to thespeed or on the drive this indicates that the CD-ROM uses CAV or Constant Angular Velocity to access the dataon the CD. Originally CD-ROM drives utilized CLV or Constant Linear Velocity where the information wasobtained of the CD-ROM drive was accessed slower / faster by adjusting the speed of the motor which allowsthe data to be transferred at a steady flow.

With CAV the CD rotates at a constant speed without adjusting when at a different location on the CD whichmeans a 32x speed CD-ROM for example will be able to access the data 32x on the outside layer howeverwhen approaching the middle of the CD-ROM drive the access speed can decrease close to 20x.

seek timeLike latency, seek time is a measurement of the read/write performance of a disk drive. For a magnetic diskdrive, seek time is the amount of time it takes to move the read/write head from its current track to the trackwhere data is to be read from or written to. For a CD-ROM drive, seek time is the amount of time it takes toposition the laser beam over the portion of the CDs single spiraling track that contains the data to be read. Seektime is used to assess disk drive performance.

latencyLike seek time, latency is a measurement of the read/write performance of a disk drive. Latency is the time ittakes for a particular sector to pass under the read/write head of a disk after the head is positioned over theappropriate disk track. The maximum latency for a magnetic disk is the time it takes for a complete rotation of adisk; the average latency of a magnetic disk is half the time of a complete rotation, assuming the sectors arerequested at random. For a CD-ROM, the latency is the time it takes for a particular sector to pass under the

laser beam after the photodetector is positioned an appropriate distance from the edge of the disk.

A 7200 rpm drive has a rotational latency of 4.15 ms on average. A 4500 rpm drive has a rotational latency of6.67 ms on average. So a 7200 rpm drive with a seek of 12.5ms has an access time that is just as fast as a4500 rpm drive with a seek of 10.0 ms.


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Iomega's marketing uses comparable CD recording speeds to demonstrate the prowess of its new Zip 750MB,but marketing rarely lives up to reality. For our comparison, we pitted the Zip 750MB against the $220 TDKveloCD 40x USB 2.0 CD recorder.

We used three sets of test files to measure the performance of each drive. We used Nero 5.5 as our CDauthoring application and Windows Explorer for everything else, including reading and writing to the Zip 750MB.

Test 1: Ten files totaling 644MB Test 2: Folder containing over 5,300 files and 90 folders totaling 289MB Test 3: Folder containing 160 .MP3s totaling 645MB.

Write testsWe tested the Zip 750MB's write performance against 12x rated CD-RW media. The results are in MB/s, withhigher being better.

CD-RW VS Zip 750MB Write Test: results in MB/s, higher is better Test 1 Test 2 Test 3

Zip 750MB 2.58 1.17 1.56

TDK veloCD 40/12/48 1.58 1.29 1.58

% faster than Zip 750 63.2%slower

9.30% 1.26%

The veloCD with 12x rewritable media loses Test 1 quite handily to the Zip 750MB. However, tests 2 and 3 haveTDK's drive pulling ahead with small leads. As a reference point, the difference in recording time between bothdrives for Test 1 was just over 2.5 minutes.

Read testsOur results are in MB/s, with higher numbers being better.

CD-RW VS Zip 750MB Read Test: results in MB/s, higher is better Test 1 Test 2 Test 3

Zip 750MB 4.74 1.84 4.51

TDK veloCD 40/12/48 3.46 2.18 3.31

% faster than veloCD 40/12/48 36.9% 18.5%slower

36.2%

The Zip 750MB gained two strong wins. Test 2 is a folder containing over 5,400 files, and our results highlightthe increased overhead generated when trying to transfer many small files.

Regardless of Windows' removable media optimization settings, the veloCD using CD-R (write once)media was faster than the Zip 750MB in every one of our read/write tests.

Depending on the optimization settings, the veloCD was able to write data 20-665 percent (yes, over 6x)faster than the Zip 750MB. Read speeds were a bit less dramatic with the veloCD managing a 5-48percent advantage.

Our use of CD rewritable media evened the playing field when comparing the Zip 750MB to the veloCD, butblank media costs are difficult to ignore. While it is easy to find bulk CD-R/RW media for under $1 a disc,estimated prices of an eight-pack of 750MB Zip disks put the cost per disc at about $12.50.

For users who want a hard-drive-like environment to store their files, with the ability to quickly and easilypassword-protect a disk, the Zip 750MB provides the means. Zip cartridges do a better job of protecting themagnetic media within, but its estimated life of five years with regular usage is about a tenth of that of a CD.

Summary: The Zip 750MB offers performance comparable to CD recorders, but it isn't as easy to share.Pros: Rugged media; small drive footprint.Cons: Not as fast as CD-R; expensive media; cannot write to 100MB Zip disks

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CD-DVD Speed Tutoriall