On 2003-02-16 at 06:21:24 [-0800], Ingo Weinhold wrote: > > [...] > > > Er, I probably just don't know about multi-session CDs. A CD > > > doesn't > > > simply consist of sessions, but these sessions are grouped in > > > volumes?? > > > If that is so, it should be an information the Disk Device API is > > > able > > > to provide. > > > > With iso9660 file systems, you can refer to file data from previous > > sessions instead of duplicating the same data over again. So, say > > you > > have 20 files that you back up on a CD. Then a week later, you want > > to > > back them up again, but only one of them has changed. Instead of > > writing all 20 files again, only the changed file will be written, > > and > > the remaining entries will just refer to the data in the previous > > session. > > Mmh, that doesn't sound like something I like. If I understand you > correctly, the file system needs to access other sessions than the one > passed to it. I believe so. I don't fully understand how it all works though, so I could be wrong. > > So, I think that it's not really a session add-on thing as much as a > > file system add-on thing. With iso9660, I believe all the related > > volumes have a common "volume set" identifier (I'd need to double > > check > > this, though). We'd probably need something similar to be able to > > distinquish which volumes are part of a set and which volumes are > > independent. We'd probably also need a way to designate the > > chronological ordering of the volumes; either a datestamp or an > > ordinal numbering, I suppose. I'm nearly done revamping the session > > module, so I could look into the details of how iso9960 handles > > things > > after I finish. Thoughts? > Off the top of my head: > Can you please elaborate a bit more on this -- best starting with the > terminology. E.g. what is a volume? Is it a session, a track or a > partition? Just a recognized chunk of data formatted with iso9660, so I guess a partition, from where we're coming from. I don't recall seeing this nailed down very precisely in the standard. Volume is just the terminology the iso9660 specs use. > What is the volume set identifier -- a string, an int? I believe a string, but I could be wrong. I'm not even sure that's exactly what the volume set identifier is used for (again, the specs are fuzzy), but I haven't had a chance to check yet. > What > about the chronological order of the volumes on disk -- is it implied > (by the order of appearance) or explicit (time stamp)? Not sure. Possibly both. > When should a > session, volume or volume set (or whatever) be invisible for the user, > i.e. is the session,... burned latest always the only one visible, or, > if not in general, under what circumstances? ...? This is, afaik, not defined. Windows always presents the last session on the CD, regardless of whether it is part of a set (even if there are previous sessions that are *not* part of any set). R5 presents everything. I would like to see us present the last session of each set on the CD by default (treating independent sessions as one-volume sets), and offer the option of choosing or switching to earlier sessions for multi-volume sets. > To save you some time, maybe it's better, if you sent a link. As you > like... :-) I will email you the specs, as I forget where I got them from originally. :-) If you feel like playing with the volume descriptors on an iso CD, the iso9660 add-on loops through all the descriptors on a volume, and can easily be made to print out more information about/from each it encounters. > I really want to understand the problem completely first. Understood. :-) I certainly don't fully understand it at the moment either. :-/ -Tyler