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11-15-2010, 08:53 PM
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Here are a few fairly jargon-free explanations of how the wobble groove of a DVD functions to allow read/write of the various recordable DVD media. Refer to the Optodisc images of a DVD-RW while reading the descriptions.

from Optodisc:
Quote:
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Note that DVD-RW is "ATIP" and DVD+RW is "ADIP" (more on that in the texts below) -- so the bottom "white background" images are not entirely accurate. The data direction in conjunction with the grooves for the DVD-RAM is also a bit misleading (i.e., should be stacked vertically, not side-by-side). I'll have to correct this at some point. The "DVD-RW" is actually a "DVD+RW" as a true DVD-RW would have ATIP with LPP notches along the land. (Note that the top "colorful" image is accurate for DVD-R/DVD-RW.)

from unknown original source (found on PCTechGuide site):
Quote:
Note that the Optodisc image was a slice view of a disc with the laser side down, while the PC Tech Guide image has the disc upside-down (as denoted by the laser beam being shown on the wobble groove).

from Sony (RDR-GX7 DVD recorder manual):
Quote:
Different types of physical formats -- The physical formats of all recordable DVD can be roughly divided into two categories: the “wobble groove” type which includes DVD-RW, DVD-R, DVD+RW and DVD+R; and “wobble land groove” type of DVD-RAM. The disc surface can be configured with the following types of features: lands (protrusions), grooves, pits (the recorded points) and wobbles (snake-like patterns). Lands and grooves are like guides which enable correct tracking of the laser light beam during recording, with wobbles used within the land grooves as markers to indicate the circumference direction.

DVD-RW and DVD-R physical format -- The physical format of DVD-RW and DVD-R discs uses wobbled grooves, just like CD-RWand CD-R. Wobbles in the grooves and breaks in the land areas called land pre-pits (LPP) are used to perform addressing. Recording pits are only located in the groove areas. Track pitch is 0.74 microns, the same as DVD-ROM, with the light reflection ratio of DVD-R roughly the same as that of DVD-ROM single layer, and the light reflection ratio of DVD-RWroughly the same as that of DVD-ROM dual layer. For both discs, physical construction is very close to that of a playback-only DVD-Video disc.

DVD+RW and DVD+R physical format -- The physical format of DVD+RW and DVD+R uses wobbled grooves, just like DVD-RWand DVD-R. Track pitch is also the same at 0.74 microns. The biggest difference between DVD+RW/+R and DVD-RW/-R is that the wobbles of DVD+RW/+R are much finer. This is called a “high frequency wobble.” The fineness of the wobble is some 37.1 times that of CD-RW/-R to enable addressing control with much higher precision since the recording density of DVD is much higher than that of CD-RW/-R. The use of this high frequency wobble enables a form of additional data recording technology without breaks called “loss-less linking.” For random writing common in PC data recording, loss-less linking reduces the data error generation ratio. While loss-less linking is specified as a requirement for the DVD+RWformat, it is an option on the DVD-RW format.

DVD-RAM physical format -- The physical format of DVD-RAM uses wobbled land and grooves. Recorded pits are formed on both the land and groove tracks, while track pitch is slightly smaller at 0.615 microns. These features differentiate it from the other types of discs explained in this section. In addition, DVD-RAM also employs Zoned CLV (Constant Linear Velocity) and an address information area in the breaks between recorded tracks, making data distribution completely different from that of playback-only DVD. Accordingly, special playback equipment is required for DVD-RAM. For this reason, DVD-RAM is considered a format in which priority is placed on having a higher number of re-write cycles, rather than on playback compatibility
from Wikipedia (DVD-R):
Quote:
In a DVD-R, the addressing (the determination of location of the laser beam on the disc) is done with additional pits and lands (called land pre-pits) in the areas between the grooves. The groove on a DVD-R disc has a constant wobble frequency used for motor control, etc.
from Sony patent US#7826319 (Optical disc record medium, disc production method, recording apparatus):
Quote:
In an optical disc record medium on which data are capable of being recorded, for example CD-R (Compact Disc-Recordable), DVD-R (Digital Versatile Disc-Recordable) or DVD-RW (ReWritable), a helical guide groove (hereinafter may be referred to asa groove) is formed at a predetermined track pitch. Information is recorded in the guide groove or a portion formed between adjacent paths formed thereof as tracks. In these recordable discs, rotation control information for a spindle motor and addressinformation are recorded by wobbling the groove. In other words, to record data on a record medium, it is necessary to control a spindle motor to rotate at a predetermined rotation rate. The rotation rate is controlled so that a rotation synchronoussignal (rotation control information) obtained on the basis of a detection result of wobbling of the groove becomes a predetermined frequency. For example, CLV (Constant Linear Velocity) that keeps a linear velocity constant is used. In addition, an access to a predetermined address is accomplished with address information embedded as wobbles.

FIG. 1 shows an example of wobbling of a groove formed on a disc 100 of related art. In this drawing, a part of the disc 100 of related art is cut out and the shape of the data record surface is shown with a perspective view. In FIG. 1, a guidegroove 102 is helically formed on the data record surface of the disc 100. The guide groove 102 is wobbled on the basis of the foregoing rotation control information, address information, and so forth. The guide groove 102 is wobbled on the basis of anFM signal. In other words, a predetermined frequency as the rotation control information is referred to as a carrier frequency. The carrier frequency is frequency-modulated on the basis of address information. The guide groove 102 is wobbled on thebasis of a signal obtained as the result of the FM signal. When a drive device side records data on the disc 100, since a tracking error signal contains an frequency modulation (FM) signal on the basis of the wobbling of the guide groove 102, the FM signal is extracted by a band pass filter or the like. The carrier (center frequency) of the FM signal is detected as the rotation control signal. The address information is obtained by demodulating the FM signal itself.

For CD-ROM and MD (Mini Disc), the center frequency of the wobbling is set at for example 22.05 kHz.+-.1 kHz so that it does not adversely affect tracking servo and data reproduction. Likewise, for DVD-R and DVD+R, for example 140.6 kHz and 817.4 kHz are selected as their center frequencies of the wobbling, respectively, so that they do not adversely affect tracking servo and data reproduction.

Thus, the recordable discs of related art have a feature in that desired information such as rotation control information and address information are recorded by wobbling a groove. Information recorded by wobbling a groove can be detected with a push-pull signal. Thus, even if a groove is slightly wobbled, it can be detected with a relatively high sensitivity. Many drive devices are provided with a push-pull signal detection unit so as to detect wobbling of a groove with a high accuracy insuch a manner.

Some drive devices for optical disc record mediums may be provided with a mechanism that detects wobbling and determines whether a loaded optical disc is a recordable disc. When the mechanism has determined that the loaded disc be a recordable disc, the mechanism may restrict the operation of the drive device.

The type of a disc has been determined by the determination mechanism mainly for countermeasures against pirated discs. In other words, it can be considered that there is a case of which content of an optical disc record medium sold as are production-only (ROM) disc is illegally copied to recordable discs without permission of the copyright owner and the copied discs are supplied as so-called pirated discs. To prevent such pirated discs from being produced, it is determined whether thetype of a disc is recordable depending on whether wobbling has been detected. When the determined result denotes that the disc is a recordable disc and the recorded content is reproduction-only content, assuming that the disc is a pirated disc, thereproduction of content is stopped.

It can be determined whether the content is reproduction-only content depending on whether the content has been encrypted according to CCS (Contents Scrambling System) method.

It is needless to say that such countermeasures against pirated discs have been effective and are important to protect legal rights of copyright owners. However, in recent years, as optical disc record mediums have been widely used, situationfor such countermeasures is becoming changed. In other words, legal copyright owners are wanting to intentionally record content to recordable discs and distribute them. It can be said that since reproduction-only ROM discs have a simple structure,resulting in excellent mass producibility and high cost-performance, they are very suitable for mediums for content to be mass-distributed. However, this condition is applied only for the case that the number of discs produced is large. If the number of discs produced is small, the cost for reproduction-only ROM discs may be higher than that for recordable discs with respect to the total cost from production of a disc master to production of final products. Thus, the copyright owner side is desiring to distribute content with recordable discs in the case that mass-distribution of content is not expectable.

However, as can be understood from the foregoing description, wobbles are formed on recordable discs. Thus, if content of a ROM disc has been simply recorded on a recordable disc and distributed therewith, when a user's drive device reproduces the content from the recordable disc, the device detects wobbles, incorrectly determines that the disc be a pirated disc, and stops the reproduction of the content.

As a solution in such a situation, it is thought that rotation control information for a spindle motor, address information, and so forth are recorded without a wobble signal. As a technology that accomplishes such a solution, there is forexample Japanese Patent Application Laid-Open No. HEI 9-17033 (patent document 1). Specifically, in the technology of patent document 1, as shown in FIG. 2, the width of a groove is partly enlarged. Information is recorded depending on whether thereare enlarged width portions in a groove. In this method, since required information such as address information can be recorded without necessity of wobbling a groove, a drive device provided with such a determination mechanism can prevent a recordable disc on which reproduction-only content has been recorded from being incorrectly determined to be a pirated disc.
from unknown original sources (found on MT Solutions site):
Quote:
Recordable disc radial grooves are sinusoidal bending mode (snake-like). This structure is called wobble. There are two wobble frequency for recordable CD, DVD-R(W) uses 140.6KHz, while the DVD+R(W) uses 817.4 KHz. The wobble loads the information of the recordable CD. It can provide tracking information and speed information. The addressing information veries according to formats.

- ATIP (Absolute Time in Pre-groove), which is to concoct the time into the wobble.
- ADIP (Address in Pre-groove, wich is also to conduct the time code into wobble.

The grooves of DVD-R, DVD-RW, DVD+R and DVD+RW are spiral shaped. The DVD-R and DVD-RW are set with LPP (land pre pit) with addressing information. DVD+R(W) have a higher wobble frequency than that of DVD-R(W). The addressing information is loaded on the Phase Modulation of groove, so it is also called ADIP.

The rut of pre-grooves DVD-R and DVD-RW is concocted with ATIP and the address information is provided by the LPP.The pre pit shall offer the amplitude peak of the wobble signal of the groove. The pre-groove of DVD+R and DVD+RW using a ADIP way with information loaded on the phase modulation of the groove.

DVD-RAM has special pre-grooves with a shape of concentric circle. The groove is separated by sector head, the inner circle has molding information area as the left picture shows below.The address information is molded onto the sector head.The most important is that the pit and land can be loaded with data as the right picture shows below.



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Last edited by kpmedia; 11-15-2010 at 11:12 PM.
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11-15-2010, 11:08 PM
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more from Philips:
Quote:
Write Strategies for high performance DVD+R/RW

Successful recording of DVD discs at higher recording speeds and of dual layer versions mandates a very accurate matching between disc and recorder. Today the media ID (MID) recognition, as inherited from CD-R, is a popular way of achieving the disc-drive match for recording. However, this procedure only works for known discs.

Known discs: (1) discs that have been tested by the drive manufacturer for write strategy AND (2) drive firmware contains best write strategy in the media table.

For new discs or changed discs these two essential conditions are not met. The result is that the media ID (MID) recognition does not work properly. (1) The drive does not recognize MID Code - no satisfactory default write strategy; or (2) The drive recognizes MID Code but no reliable write strategy data is available - the drive applies an unreliable default strategy for the new disc yielding inaccurate recording and data read-back problems.

The Extended Information Blocks as contained in the ADIP of DVD+R/RW provides all write strategy information the drive needs for an accurate recording. All disc manufacturers and drive makers are strongly advised to fully use this functionality as offered by the DVD+R/RW format. Its the most adequate solution possible to the increasing demands on media and drives. It also solves all the problems related to the fast growing supply base.

With this advised procedure, all drive manufacturers still can use the Manufacturer/Type ID look-up table in their product. This guarantees the optimum recording condition for the specific drive and disc combination. This is only true for those discs that were physically tested by the drive maker. For all other instances the MID Code recognition (like a 'generic' MID Code) does not give satisfactory results, especially for the higher recording speed conditions.

The Write Strategy for a drive based on ADIP, optionally extended with media ID (MID) recognition, is considered to be the most reliable and solid solution for disc manufacturers and drive makers. This has been fully described in the DVD+R/RW standard specifications (Annex "How to use the physical format in ADIP"). In attached document every licensed disc manufacturercan apply for his disc and process specific ADIP and MID Code information.
Note that the last paragraph is very propaganda-like, insinuating some sort of superiority over DVD-R (the DVD Forum format recordable DVDs).

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