FreeLists / openbeosstorage / [openbeosstorage] Joliet Multisession Extensions

[Tyler Dauwalder <tyler@xxxxxxxxxxxxx>]

While working on Joliet support, I came across the following. It 
explains why Windows always presents only the last session on a disc, 
and possibly why we're seeing absolute addresses all over the place 
(even though this doesn't justify using them in plain old iso9660 
descriptors). 

From:
http://www-plateau.cs.berkeley.edu/people/chaffee/jolspec.html

-----------------------------
Joliet for Multisession Media
-----------------------------

Multisession Recordings are Received
------------------------------------
When provided with CD-ROM reader hardware with multisession 
capability, Joliet receiving systems shall receive media recorded 
using the multisession recording technique.

The details of this technique are provided below


Logical Sector Addressing on Multisession Recordings
----------------------------------------------------
Each sector on the media is assigned a unique Logical Sector Address.

Logical Sector Addresses zero and above increase linearly across the 
surface of the disc, regardless of session boundaries.

Logical Sector Address zero references the sector with 
Minute:Second:Frame address 00:02:00 in the first session. All other 
Logical Sector Addresses are relative to Minute:Second:Frame address 
00:02:00 in the first session.

The conversion between Logical Sector Addresses and 
Minute:Second:Frame addresses is Logical Sector Address = 
(((Minute*60)+Seconds)*75) - 150.

Simply put, the Logical Sector Address on a multisession disc 
describes a flat address space.


Multisession Addressability
----------------------------
The data area for a volume may span multiple sessions.

For example, if a disc is recorded with 3 sessions, the directory 
hierarchy described by a volume descriptor in session 3 may reference 
logical sectors recorded in session 1, 2, or 3.


Multisession Volume Recognition Sequence
----------------------------------------

The Volume Recognition Sequence shall begin at the 16th logical 
sector of the first track of the last session on the disc.

This volume recognition sequence supersedes all other volume 
recognition sequences on the disc. The interpretation of the Volume 
Recognition Sequence is otherwise unchanged.

For example, consider a disc that contains 3 sessions, where session 
1 starts at 00:00:00, session 2 starts at 10:00:00, and session 3 
starts at 20:00:00. The Volume Recognition Sequence for this disc 
would start at Minute:Second:Frame address 20:00:16.

This technique is compatible with the CD-Bridge multisession 
technique.

-Tyler