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Re: [Bug-xorriso] To Thomas Schmitt: how to go on, xorriso is installed

From: Thomas Schmitt
Subject: Re: [Bug-xorriso] To Thomas Schmitt: how to go on, xorriso is installed
Date: Fri, 19 Apr 2019 15:05:22 +0200


Adalbert Hanßen wrote:
> I found one package of 5 unused Octron CD-RW (700 MB, 4-12x Speed),

CD-RW are good for experiments.

To make a written CD-RW re-usable from scratch again, do:

  xorriso -outdev /dev/sr0 -blank fast -eject all

Elsewise CD-RW behaves like CD-R. Just a bit slower and thus less noisy.

> unused Octron DVD+R 4.7GB 4xSpeed with a sign "RW" on it

Then they are probably DVD+RW.
Ask one of them by

  xorriso -outdev /dev/sr0 -toc

whether it is

  Media current: DVD+RW


  Media current: DVD+R

These types behave very differently. DVD+R is somewhat similar to CD-R
by offering multi-session by hardware.
DVD+RW is similar to DVD-RAM and BD-RE: Random read-write. No hardware
management of multi-session. (But xorriso can emulate such a management
by help of the ISO 9660 filesystem size info.)

DVD+R would best be used for archival of data.
DVD+RW was my bread-and-butter backup medium until i mostly switched
to BD-RE media.

> Now I have also checked the type of the T410's CD/DVD drive:
> ...
> ...
> ... 01 07 10 04 1f 00 00 00 ...
> ...
> If I understood you right, this one does not claim ability of stream
> recording.

It states that it will do it. But not now.

"01 07" is the feature code. "10" (hex, not decimal) combines Version,
Persistent, Current in one byte. Version is 4, Persistent (bit 1) is 0,
and Current (bit 0) is 0 too.
"04" tells the number of feature data bytes. The first of them, with
hex value "1f" has bit 0 set. So Stream Recording is possible under some
circumstances. But Current = 0 says "not now".

The liar says:

  01 07 15 04 1f 00 00 00

Here, Current is 1 and bit 0 of the first feature data byte is set.
This means "Stream Recording is possible right now".

> vendor 'MATSHITA' product 'DVD-RAM UJ892' revision 'SB01'
> meldet: kein StreamRecording

At least not with the appendable CD-R. Most probably not with any CD.

> It is hard to find technical information on this feature "Stream recording".

It hides itself in the many other technical occasions of "streaming".

The MMC part of SCSI specs mentions that it overrides the Defect Management
of some media. I.e. no checkreading while writing, no hopping to
replacement blocks if a block in the nromal address sequence does not
look good.
(Sounds like a bad idea. Would be, if not Defect Management was such an
 annoyance in practice. It sucks.)

>  When doese ot make sense at all?

When the drive would do Defect Management by default.

In its oldest form it is called "MRW"
It never made it much into practice, probably because people could compare
its performance with the same media without "MRW" management.

Then came DVD-RAM. Announced as the most reliable of DVD types, it quickly
lost market share because it is slow and fails like an old Iomega ZIP Clam
when the medium really has flaws.
Ok. Nearly nobody buys DVD-RAM. So no workaround was really needed.

But when Blu-ray came, the re-usable medium type BD-RE had the same
Defect Management as DVD-RAM. Nominally able of 2 x 4.5 MB/s, this
slowed them down to 4 MB/s or even 1 MB/s.
This had to stop. Stream Recording was the way to do it.

The one-time usable type BD-R can be formatted before use, so that it
can do Defect Management too. The nominal speed is 4x, 6x, or 8x.
So the slowdown to half or a third of nominal speed is more bearable
than with BD-RE media.

All these media types have a better write result if Defect Management is
disabled at write time and checkreading is done afterwards by normal
read operations.
The combined time of pure writing and pure reading is never larger than
the time needed for writing and reading by Defect Management.

> http://forums.system-rescue-cd.org/viewtopic.php?t=5660
> "[...] the burn can fail and leave
>  you with a drinks coaster for a disk if it is not a CD-RW or DVDRW."

If only fletch31337 had reported this where i had seen it.
Then at least your honest drives would not have been in danger to spoil
your CD-Rs.

> The last one should be given a warning that stream recording might go wrong!

Yes. libburn versions before (future) 1.5.2 blindly follow the urge of
Xfburn to do it.
Beginning with 1.5.2 they will do only if the drive promises to do it
and even then only with the media types where some benefit can be

Have a nice day :)


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