Partial-CAV versus Zone-CLV - Page 1
CD recorder manufacturers seeking to achieve ultra high writing speeds have
been constantly developing new techniques, enhancing older ones and applying
any sort of tweaking to their drives. Sanyo was the first company that announced
a Zone-Constant Linear Velocity (Z-CLV) recorder. The only other manufacturer
who has developed a rivaling technology is Yamaha, with Partial Constant Angular
As most readers of this review might be aware off, the original
CD reading and recording standards called for the laser beam to follow a spiral
movement of constant velocity under the track pits (the 1's and 0's). Hence,
until recently, all recorders used to record these "pits" using the
CLV (Constant Linear Velocity) method.
Things, however, have drastically changed recently. New recording
technologies have been introduced: Z-CLV and P-CAV respectively.
CD recording fans are expected to ask: What are them? How can
they be compared against each other? Which technology is faster/better? So,
let's find out. We start our journey into some of the more esoteric aspects
of recording. Follow us :-)
- Zone-CLV writing technology
Zone-CLV (Constant Linear Velocity) is the recording method being
in use lately by many End-drive manufacturers in order to achieve a higher recording
speed. All previous recorders used CLV (constant linear velocity) as the main
recording method. The rotation speed, in the inside, of a disc at 16x recording
speed reaches up to 8000rpm! The high rotation causes problems on the recorder's
mechanism and produces loud noise. Sanyo pioneered the development of the Zone-CLV
recording method trying to overcome the above two problems by making use of
the latest available manufacturing technologies. When a recorder utilizes the
current implementation of the Z-CLV recording method, the CD surface is divided
into exactly 3 zones. In each one of these zones, starting from the inner to
the outer parts of the CD, the recording speed varies.
you can see in the left picture, the recording speed at zone-1 (inner part of
the disc) is 16x, it then increases throughout zone-2 (at exactly time t1) at
20x and finally reaches an 24x-recording speed at zone-3 (after time t2).
A very interesting (and important) question then arises: how
can the drive change instantaneously its motor speed? How can it adapt the laser-beam
power and continue writing without actually destroying the disk? The question
is indeed very simple: BURN-Proof!!!
This technology (or some other of its rivaling variants) can
be used for executing the necessary synchronization between adjacent zones (Zone-1/Zone-2
and Zone-2/Zone-3 in this case). There is no imperceptible gap between the various
Zones, at least this is what Sanyo states. (How about testing this claim? Read
on and you will be certainly rewarded
- P-CAV writing technology
contrast to the Z-CLV recording technology, the P-CAV method keeps the disc
rotation constant in the inner portion of the disc and then it gradually lets
it drop down as the laser beam reaches a certain predefined distance from the
center of it.. In this scenario the actual linear writing speed smoothly accelerates
outwards, until it reaches a top limit. After this point, the writing speed
is kept constant (CLV) until the end of the recording phase, as it was done
in the past.
This new recording methodology has been developed by Yamaha and has been implemented
in all its latest drive models. It is known that at the outer part of a disc
there can be recorded 2.5 as many bits as in the inner part of it. Simple arithmetic
states that during CLV recording the speed is consequently reduced 2.5 times
in the outer part. Conversely, in Full-CAV mode (under a constant motor rotating
speed) recording speed should be 2.5 times faster in the outer part.
In the current Yamaha implementation of the P-CAV method, the
rotation speed is kept moderate (5500 rpm) in the inner portion of the disc.
Compare this with the Z-CLV method where the disc spins at over 9000rpm in the
inner part. This helps towards achieving an improved recording quality in the
inner portion of the disc. This is due to the fact that a moderate disc rotation
reduces the vibration that usually is the sole responsible for corrupting quality
during this recording phase.
Moreover, as the rotation speed is kept low, the life of both
the laser diode and the drive's pickup mechanism is expected to be extended.
If Yamaha had allowed full-CAV, the recording speed would have easily reached
30x! So expect more speedy drives in the immediate future from this manufacturer.
- P-CAV vs. Z-CLV
Z-CLV recording method of Sanyo utilizes the existing CLV method combined with
linking technology developed (and in this case exclusively used) for buffer
underrun protection. The writing of a disc is divided into several zones, and
the writing speed is kept constant within each zone. When it shifts up to the
next speed level, writing is suspended and then restarted using the buffer underrun
You can easily see that small gaps are silently being introduced during this
recording method. Hence some objections are raised by other laser manufacturers.
Specifically, Yamaha claims that the P-CAV technology is ideal for Audio CDs
and pre-mastering a disc for mass duplication, since no links are produced.
Other manufacturers say that Z-CLV doesn't affect writing quality since the
link is kept very small, almost down to zero. Of course a disc without any links
, in theory will have better quality than with links, however small these are.
But can this proved in real life?
- Tested drives
Yamaha 2200E firmware 1.0C
Sanyo CRD-BP1500P firmware vHg.35
Acer CRW2010 firmware vH.KF
LiteOn LTR-24102B firmware v5S.04
PleXWriter PX-W2410A firmware v1.00
Ricoh MP7200 firmware v1.30
Ricoh MP9200 firmware v1.00
- Tested Media
Ricoh 74min 24x Serial Number: C301R1XXXXXXXXXXX
ATIP start of lead in: -02:32:09 (sector: -11409)
ATIP start of lead out: 74:12:00 (sector: 333900)
Manufacturer code: 97 27 66 - Ricoh Company Limited (Type: 6)
Disc subtype: Medium Type C, low Beta category (C-)
Target writing power: 4
- Testing lab