[Debburn-devel] Querying the state (fixation, multi-session) of a CD-R

[Thomas Schmitt]

Hi,

> Some months ago I used wodim to write audio tracks to a CD-R disc,
> with the intent of keeping it "open" for further writes. I say
> "intent" because I don't thoroughly understand the effect of options
> like -nofix, -multi... 

I know some about MMC, few about cdrecord, and even fewer
about CD audio reading resp. playing.

-multi keeps a CD "appendable", i.e. ready for taking more tracks.
It is a MMC standards compliant option for CD-R[W], DVD-R[W], DVD+R
and BD-R if they are not formatted as (pseudo-)random access media.

-nofix on the MMC level seems to be about not performing
the CLOSE SESSION command after all tracks are written.
"Fixate" is a peculiar term not found in MMC. The only
occurence is an error code:
  5 30 09 CURRENT SESSION NOT FIXATED FOR APPEND
cdrecord issues a message "Fixating" when it closes a -tao
session.


> I don't manage to append more audio tracks to the disc

Are there any symptoms ?
Like messages ? Or more dramatic effects ?
Do the new tracks just not show up on the player ?

> - How may I retrieve info about the disc that will tell me with which
> options it was written?
> - I suspect I used -nofix together with -multi and -sao, and probably
> it doesn't make sense. If I '-fix' it, will it be readable on a
> CD-Reader?

If it does not play in the reader anyway, then -fix
might be worth a try. (From my view, a CD with an
inaccurate TOC is an abomination. Shudder.)

Many of the options will not be deducible. Like the file
names of the original audio files on your hard disk.

I don't know how to inquire appendability of a CD by
help of wodim.
With my own program cdrskin it would be

  cdrskin dev=/dev/sr0 -toc 2>/dev/null | grep 'cdrskin: status'

which with an appendable -multi CD replies:
  cdrskin: status 3 BURN_DISC_APPENDABLE "There is an incomplete disc in the drive"
and with closed (i.e. non-multi = non-writeable) CD:
  cdrskin: status 4 burn_disc_full "There is a disc with data on it in the drive"


> - May the -nofix option be combined with any mode (tao and sao)? e.g.
> if I want to write a pair of audio tracks which will play
> continuously, without blank between them, may I use -sao -nofix? If
> yes, is there any reason to use -tao -nofix?

I understand from man wodim that -nofix might be a way to
hide from the CD reader the fact that the CD was written
in multiple sessions.
Whether this implies -multi is unclear.
It can hardly do harm to use -multi as long as one
does not want to finally close the media.

On the MMC level my theory about omitting CLOSE SESSION raises
the question whether it has an effect on -sao at all.
With -sao there is no CLOSE SESSION supposed to be done
anyway.


My general info about -audio , -sao , -tao is:

By -sao you may write several tracks seamlessly within the
first session i.e. in one single run of the burn program
on blank media.
After that first session you may only write in -tao mode
which implies audible gaps.
There might be audio CD players which do not recognize
multi-session CDs. (That -nofix hack must have some
reason, after all.)


> - Is -multi specific to data discs?

It is a general feature described in MMC specs.
No reservations are made in respect to audio.
But the CD audio players are not necessarily
compliant to MMC.


> - Could you point me to a doc that will spare you answering such
> basic questions? :-D

If you find one, tell me.
Many info about CD is jailed in proprietary specs.


Have a nice day :)

Thomas