Do BD drives prior to BDXL standards support reading the new BDs partially?


#1

The BDXL standard from 2010 defines 33GB per layer, where as the legacy standard defines 25GB and only up to 2 layers.

Therefore, a legacy BD drive such as iHOS104 won’t cope with anything above BD-R DL.

But I have two questions:

  • Is it able to read the *SL models of the new BDXL standard discs (33 GB per layer)?
  • Is it able to read L0 (the first layer) from BD-TL/BD-QL?

#2

It won’t recognize the disc - just tried TL BD in legacy BD drive.

The problem is not the layer break, problem is pit formation/size. Even if the OPU lens and the drive chipset are capable of dealing with smaller pits (highly unlikely) still it would be necessary to do a complete firmware rework for the drive to become compatible with the new standard.

From the BD whitepaper.


#3

Where are the 8cm BDs mentioned?.


#4

They are mentioned in the same document but not in great detail:

“… All other formats adopt a Bare disc in Part1 and UDF (Universal Disk Format),
highly compatible with PC environment, in Part2. The storage capacity is 25 GB (for Single-Layer disc),
50 GB (for Dual-Layer disc), 100 GB (for Triple-Layer disc) and 128 GB (for Quadruple-Layer disc).
Part1 of either R or RE defines an 8 cm disc of which capacity is 7.8 GB for Single-Layer disc or 15.6
GB for Dual-Layer disc. Either ROM disc, BDXL™ disc has no 8 cm disc defined.”


#5

Too bad.
32 GB on one really compact 8cm disc would be pretty useful.


#6

I guess the manufacturing costs are to high and the demand to low.

At least a 12cm-media stores much more, can be read and write faster, have usually a lower price/GB. And all my store-cases/folders are made for 12cm, so 8cm-discs will need the same space in it.


#7

I see.
Yes, 12cm is faster, but 8cm has around 30% less access time due to the lower diameter.

But it would just be cute holding a massive 30GB inside a little 8cm disc.
This is a market gap that HD-DVD could have attacked.

HD-DVD just took a wrong approach against BluRay.
HD-DVD is more robust due to the advantageous position of the data layer: in the exact middle like DVD.

As already said, in my opinion, both should exist.


#8

Because I never had any HD-DVD I would not say it´s good or bad. Personal experience is: The price decide about quality. It was the same with every media I get, CD, DVD, BD. Some last decades, some only a few month

Access times are not important in this case, if you use often data with small files you will never use optical media with 1000x higher access times than Flash storage.

BTW, the access times not only depend on the time of positioning the laserhead, it also depends on the rotation speed of the media. Slower rpm means it cost more time til the sector pass the laserhead :wink:


#9

The rotation speed is still the same, usually.

In my opinion, disc drives should rotate 8cn discs faster.
Then, an 8cm CD in a slim laptop/portable external drive could rotate as fast as a 12cm disc in a desktop drive.


#10

Will 8cm read at same rpm like 12cm? I´m not sure, at least I found only 4x write speed media.


#11

No it won’t.

And even if you have an early BDXL drive that’s over a year old, it won’t even detect 4K UHD Blu-Ray discs.


#12

8cm discs should even support higher RPM’s, because a smaller diameter allows for a higher rotation speed with less structural stress.


#13

In theory, it´s true.

But the manufacturer of the drive/chipset/FW decided to read slower. In the specs of the drives the speeds for 8cm-media rarely to find


#14

This makes even less sense than Hyun Yeul Lee’s irrational and ugly changes to the Samsung Galaxy S6 smartphone.


#15

WE not always understand why something is like it is, but we cannot change it :wink: