[Debburn-devel] Wodim, GP08NU20 and DAO mode

[Thomas Schmitt]

Hi,

Campo wrote:
> The burned DVD si fully functional. The same DVD, with a different 
> DVD burner, allows to burn in DAO mode.

So it seems that the burn run was indeed in
DAO mode.
I assume commands like
  dvd+rw-mediainfo /dev/scd0
  cdrskin -v dev=/dev/scd0 -minfo
  xorriso -outdev /dev/scd0 -toc
would show it as closed media with a single
session.


> The only problem is that to mount or
> to read  the burned DVD ( I use dd to calculate MD5 hash ), you must eject
> and re-enter the DVD in the player. With the previous DVD burner, in DAO
> mode, this thing didn't happen. 

This is a well known shortcomming of Linux
block device drivers. Possibly it happens with
other operating systems too.
(What system are you using ?)

The burn programs have to send SCSI commands
directly and so the normal read/write driver
does not learn about the changes on the media.

Can it be there is a different operating system
driver in charge for the new burner ?
E.g. was the old one attached via parallel ATA ?
As far as i can google, GP08NU20 is attached via
USB.

In general you have to reload the media before
you can use Linux to read from it.
growisofs does an eject-load cycle when burning
is done. (I deem this a bit dangerous for the
inadverted user's fingers.)

------------------------------------------------

Now for the log you sent me:

> wodim: Operation not permitted. WARNING: Cannot set RR-scheduler
> WARNING: Cannot set priority using setpriority(),increased risk for buffer underruns. 
> Error: Cannot gain SYS_RAWIO capability, is wodim installed SUID root? Reason: Operation not permitted 

wodim tries to get fancy system features.
Looks like you are not root and have to
happily live without them. No problem. 


> Using Session At Once (SAO) for DVD mode.
> ...
> Starting to write CD/DVD at speed   8.0 in real SAO mode for single session.

As said, there is no SAO on DVD. By trying to
enable SAO, wodim did automatically enable DAO.
Just a matter of names in messages.


> Executing 'mode select g1' command on Bus 2 Target 0, Lun 0 timeout 200s
> CDB:  55 10 00 00 00 00 00 00 3C 00
> cmd finished after 0.000s timeout 200s

This is probably the command which sets
Mode Page 5 and should order DAO.
Regrettably wodim does not tell the payload
bytes. The lower four bits of the third byte are
supposed to form the value 2.


> Beginning DMA speed test. Set CDR_NODMATEST environment variable if device
> communication breaks or freezes immediately after that.
> ...
> Executing 'read buffer' command on Bus 2 Target 0, Lun 0 timeout 200s
> CDB:  3C 00 00 00 00 00 00 FC 00 00
> resid: 62448
> cmd finished after 0.001s timeout 200s

And here we finally have the obscure
"resid: 62448" and its SCSI command.

wodim wants to read 64512 bytes (0x0000FC00)
from the drive buffer. No error condition is
reported by the drive, but wodim and/or the
operating system decided that 62448 bytes are
missing. I.e. 2064 bytes were accounted as
received.

This is strange but should not hamper burn
success. I understand the buffer reading is only
done to measure maximum transmission speed.

> Drive DMA Speed: 74151 kB/s 421x CD 53x DVD

We shall not believe this outcome :))


> Track 01:   36 of 4199 MB written (fifo  99%)BFree: 100 K BSize: 1376 K
>  [buf  92%]   3.6x.
> ...
> Track 01: 4199 of 4199 MB written (fifo 100%)BFree: 78 K BSize: 1376 K
>  [buf  94%]   8.3x.
> ...
> Track 01: Total bytes read/written: 4403861504/4403861504 (2150323 sectors).
> Writing  time:  596.461s
> Average write speed   5.6x.

Looks like a normal write for nominal 8x media.
DVD-R and DVD+R normally begin slow and
accelarate up to nominal speed.


Summary:
All seems well. You got DAO despite the messages
about SAO and "resid".


Have a nice day :)

Thomas