[Debburn-devel] Do you know a good dvd burner emulator

Maxim Levitsky maximlevitsky at gmail.com
Tue Oct 14 19:28:08 UTC 2008

Thomas Schmitt wrote:
> Hi,
>>> The 2x Verbatims live since 2004.
>> But how many times you usually record them a day?
> Currently two of them serve in incremental backups.
> They get added a session about every fourth day.
> One took 43 sessions as sequential DVD-RW and now
> serves a second turn as formatted DVD-RW having
> 12 (pseudo-)sessions meanwhile.
> I would assume that i did not use it more than
> 50 times before. Mostly in formatted state, but
> also sequential (after 40 minutes of blanking).
>> I like linux-kernel code style, and your project is exactly what I like.
> Somehow libburn seems to stem from kernel code.
> I am not sure because i'm not its founder and
> we took over without the consent of the founders.
>> isn't there a limit (99) on track count?
> On CD media, yes. 
> Worse: you cannot write 99 sessions because there
> are gaps of more than 10 MB after each session.
> With DVD-R the gaps are about 8 MB and you can
> write lots of sessions.
> With DVD+R the gap is 4 MB but you can write only
> 153 (or 254 ?) sessions.
> (see MMC-5 for numbers 153 and FFh)
>> I would rather open a track, and write it in chunks (packets), and use
>> variable size packets, and close it when disk is unmounted.
> On CD-R[W] this might work.
> On DVD-R[W] you are restricted to a multiple of 32 KiB
> blocks. This applies to both, formatted and unformatted.
> Same with DVD+R.
> With DVD+RW you suffer a performance penalty if not
> aligned to 32 KiB.
> The natural block size for BD-R[E] is 64 KiB.
Thanks for information, didn't know that.

> But there is the restriction that you are not supposed
> to read during writing a session on sequential media.
> (MMC-5 SAO Raw on CD-R/-RW, DAO and Incremental
>  on DVD-R/-RW)
> Whether the consequences are tolerable with packet
> write modes has still to be tested.
> Currently libburn refuses to read while a write
> session is going on.
Very interesting.
It must be possible, as directcd that HP burner had treated a CD-R
disk as a floppy disk, although I didn't use that burner much, but
I remember that directcd buffered a bit of data, and then wrote it.
Windows vista also supports writing CD/DVD-R, and it writes a session per

I am really very far from this, it will take lots of time (months?) to make filesystem 

I was just worried that I won't be able to do -R support, and this is the thing linux misses

>> session probably needs to be closed to, but I think I can leave it open, and
>> close it when user explicitly asks for that.
> That would be the suspicious -nofix option of
> wodim and cdrecord.
>> (I once had HP CD burner, and it worked that way, it closed session when an
>> option "convert disk
>> so it can be read in ordinary CD" was selected.
> Are you sure it closed the session and not the disc ?
> (I.e. not -multi rather than not -nofix.)
> I read rumors that appendable media might not be
> readable in some CD players.
I am not sure.

Facts I know:

1) there was an option to "make disk readable in regular cd players"
2) after doing the above, there was a way to undo this.
(thought there was a checkbox to make undo impossible)

3) ISO bridge filesystem wasn't created during the conversion, I conclude
this from the fact that adaptec distributed a driver that allowed to read packet
formatted disks.

4) I still have a cd-r formatted in that drive.
session wasn't closed.
I accidently kept this disk, and tried it in vista, and was able to close
session there, and open new one.

> All in all i would frown on ejecting a media with
> an open session (if the drive is willing to obey
> at all).
> But as long as the media stays loaded, that long
> it should be possible to keep open a session on
> all media except fast blanked DVD-RW.
> This session should be allowed to be written
> sequentially with arbitrary idle times inbetween.
>> So for now no more questions, Thanks,
> Give me a note when you begin to feel ready for
> CD packet writing and/or formatting experiments.
> I will probably need a week from then on to
> make a first test version of libburn for that.
Thanks a lot, it will take a lot of time for me. as I almost have no
free time now. 

> The DVD stuff should already be prepared for
> experiments if you use  
>   burn_write_opts_set_write_type(
> and provide a burn_source object which puts out
> some 32 KiB blocks from time to time.
> The most interesting experiment to be made is
> whether you may read data while writing in
> packet mode to sequential media. For that
> i will have to lift the read ban in libburn.
> If not then you will have to cache your writes
> until they are large enough to be written as
> a session.
> I would expect problems at least with CD-R
> and DVD-R.
DVD-R udf disk is new for me, that HP burner 
was cd only, and accidently I only used a single cd
when testing udf in vista.

I take a dvd-r and see how vista copes with it.
> Have a nice day :)
> Thomas
Thanks a lot,
	Best regards,
		Maxim Levitsky

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