[sclug] Blu-Ray writing

Dickon Hood dickon-ml at fluff.org
Mon Jul 16 22:57:14 UTC 2012

On Mon, Jul 16, 2012 at 22:10:46 +0100, Daniel Craigie wrote:

: The drive appears in /dev/ as multiple devices:
: brw-rw----+ 1 root cdrom 11, 0 Jul  9 19:20 /dev/sr0

: lrwxrwxrwx 1 root root 3 Jul  9 19:20 /dev/cdrom -> sr0
: lrwxrwxrwx 1 root root 3 Jul  9 19:20 /dev/cdrom1 -> sr0
: lrwxrwxrwx 1 root root 3 Jul  9 19:20 /dev/cdrw -> sr0
: lrwxrwxrwx 1 root root 3 Jul  9 19:20 /dev/cdrw1 -> sr0

It doesn't.  That's one device -- /dev/sr0 (AFAICT 'SCSI ROM') -- with
some symlinks pointing to it for compatibility reasons.  Frankly, I'm
surprised; I'd've expected cdrom0 instead of cdrom1 and similar, if they
were to appear at all.  What distribution are you running?  I'm quite
surprised you don't have a /dev/dvd too.

: Am I correct to assume that the duplication of both the cdrom and cdrw
: links reference the two layers of the disk as separate disks?

No.  I've never done this, but I'm going to assume that multi-layer discs
are handled the same as they are on DVDs: one, contiguous logical set of
sectors.  It's the only model that makes sense.

: I have found sporadic info online regarding the actual process of
: writing data to the disks.  I'm not sure if the existing dvd writing
: software can cope with the amount of data that will be written to the
: disks, I fear buffer overflows and don't fancy having to throw away
: expensive & empty disks.

: Any advice greatly appreciated,

Again, it's a guess, but I would assume that something like libburn (use
the cdrskin wrapper, or similar) will write something useful to it.  Most
of the time, media of this sort tends to behave as the older generation
did, so as to not confuse anything.

mkisofs used to be able to take a directory structure and produce a stream
of objects from it, if you wanted something vaguely standard.  I'd
probably do something like that, or possibly write a raw tar, if I'm just
interested in getting the data to disc ASAP.

In short: try a DVD writer.  It'll probably do exactly what you want it
to, and, for the price of a disc, is worth testing.  And report back here
if it works -- I'm interested in similar myself, ta :-)

Dickon Hood
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