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Re: Announcing cdrskin-0.4.4



Hi,

i tested WRITE12 and Streaming bit on DVD-RAM. Up to
the first bad spot on my test media writing runs with nearly
nominal speed:
Effective 1.8x with nominal 2x DVD-RAM.

Without Streaming bit, WRITE12 and WRITE10 both perform
at 0.8x effective speed.

-----

To Giulio:

Please get the newest cdrskin-0.4.5 development tarball

  http://scdbackup.sourceforge.net/cdrskin-0.4.5.tar.gz

  $ cdrskin -version
  ...
  Version timestamp :  2008.04.12.164930
or later timestamp.

Next time you have a BD-RE formatted with spare area
please try a write run with these options:

  $ cdrskin stream_recording=on --allow_untested_media

-----

Observations with DVD-RAM:

Interesting with normal writing is that the drive buffer
bounces between 5% and 99% fill. One could well misinterpret
this as a lack of i/o bandwidth.
With Streaming bit, the drive buffer is always 99% full.

The first reproducible bad spot (after 75 MB) makes
both write variants quite unbearable. The drive gnaws
a while, plonks, and does that again several times before
going on with writing.

If this happened with Streaming bit then the media produces
lots of media error entries in /var/log/messages when trying
to read sequentially over the bad address.
With WRITE10 the same image and media are readable and
verificable afterwards. But writing of 125 MB needed more
than half an hour.
This readability is not a statistically founded observation.
I also had MD5 verification failures on DVD-RAM in the past.


With two bad spots (one around 75 MB and one at 117 MB)
it lasts 383 seconds to write 125 MB by WRITE12 Streaming.
It lasts 2024 seconds with WRITE10.
So the drive (Philips SPD3300L) and the media (Panasonic 2x
DVD-RAM) together are not really recommendable.

I will try to heal it by re-formatting in the next days.

-----

Standards consideration:

WRITE12 is not associated with the features comprising
the profiles of DVD-RAM and BD-RE.
So i cannot conclude from the presence and writeability
of a DVD-RAM or BD-RE to the availability of WRITE12.

It belongs to all other DVD+/- features, though. On my
drive it obviously has an effect on DVD-RAM writing.

Feature 107h belongs to DVD-RAM and BD-RE. It can indicate
a Stream Writing bit which promises the "Stream recording
operation". That operation seems to be associated with
WRITE12.

Another method to find out about WRITE12 would be
a test write to the start address before payload
writing begins at the same address.

I will have to think more about WRITE12.
For now it is heavily experimental.


Have a nice day :)

Thomas


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