Disc writing speeds: Which purpose has P-CAV and Z-CLV?

[TechLord]

• P-CAV = partial constant angular velocity.
• Z-CLV = zoned constant linear velocity.
• I wonder, why they're not called "P-CLV" and "Z-CAV".

I am not claiming, that these two writing patterns PCAV and ZCLV are bad.
However, I am just not sure, what their purpose is.

What are the advantages of zCLV and pCAV over normal CAV and CLV disc writing?

(One advantage is: beautiful circle phases on the disc writing surface are visible.).

[betwixt]

The data rate from the disc depends on how fast the 'pits' on its surface pass under the laser head. The difference in circumference of the innermost and outermost data areas means that for a constant rotation speed, the pits pass more quickly at the outer than the inner area. To some degree, the data speed tracking electronics can adapt to different data rates, and it does, but to be most reliable and make best use of storage capacity, it helps to adjust the rotational speed as well. One method adjusts the speed to maintain a constant data rate, the motor speed being adjusted so the data flow stays at a constant rate, the other method is similar but does it in jumps 'zones' so the data recovery circuits don't have to cater for such a wide rate variation.

Brian.

[TechLord]

The data rate from the disc depends on how fast the 'pits' on its surface pass under the laser head. The difference in circumference of the innermost and outermost data areas means that for a constant rotation speed, the pits pass more quickly at the outer than the inner area. To some degree, the data speed tracking electronics can adapt to different data rates, and it does, but to be most reliable and make best use of storage capacity, it helps to adjust the rotational speed as well. One method adjusts the speed to maintain a constant data rate, the motor speed being adjusted so the data flow stays at a constant rate, the other method is similar but does it in jumps 'zones' so the data recovery circuits don't have to cater for such a wide rate variation.

Brian.

I appreciate the work you put into the answer.
Bur a few questions are still open:

• What are "data recovery circles"? Which LBA (logical block address) do they have?
• Why do these data recovery circles require PCAV and ZCLV?
• When is ZCLV more suitable?
• When is PCAV more suitable?
• Why are they not called Z-CAV and P-CLV?

[TechLord]

Old, but interesting thread (ID 214141) I found from 2005: https://forum.videohelp.com/threads/214141-DVD-Writer-vs-Recorder-CAV-vs-CLV

[TechLord]

P-CAV can be used to maintain a maximum writing speed without downforcing the writing speed at the beginning, using CLV

Example: Writing with 32× PCAV on a desktop drive, the rotation soeed will first start with the same rotation speed used in ×48 CAV.

Inner disc edge = 48/2.4 (for 8cm disc: 1:1.6), which means, starting at ×20, accelerating until ×32, and circumcising the writing speeds above ×32 by starting CLV when hitting ×32.

PCAV meams starting with CAV, until the CLV equivalent speed reaches a specific value, which will then be maintained until the end, which causes the rotation speed (angular speed) to decrease.