Subject: Re: The demise of DEV_BSIZE
To: None <>
From: Wolfgang Solfrank <>
List: tech-kern
Date: 10/07/1999 15:27:52

> Can someone propose a possible application for sector size != 2**n?

Well, I was going to write something about it anyway, especially since it
doesn't fit with the model that's currently discussed :-(.

What I have in mind is the "CD/ROM XA Mixed Mode" format.  These do have
a form of ISO9660 filesystem.  At least the directory structure is
recorded in logical 2048 byte sectors (albeit the recording is a tiny
little bit different from the standard CD/ROM 2048 byte sectors), and
can have ordinary files recorded in this part of the disk, too.  In
addition to that, the format supports recording of "multimedia data".
These are recorded with a blocksize of 2332 bytes (if I remember
correctly, don't have the standard handy right now), since you don't
need the same amount of error correction for this kind of data.
This files maybe recorded with some interleaving, so you can for
instance mix a video file and the corresponding audio file).

I'm not sure, but I think that CDI disks are recorded in this format.

What this means for the problem at hand is that support for this type
of media would require a more dynamic handling of the blocksize.


PS: BTW, there _are_ CD drives that can address audio sectors reliably.
ws@TooLs.DE     (Wolfgang Solfrank, TooLs GmbH) 	+49-228-985800