CDROM-XA info re: VCD support on OS X

[David Nedrow]

I've been poking around trying to get some info on this for those of you
working on the port of vls/vlc to OS X.

One thing I found is that a bug report is open for this. Details at:

http://www.opensource.apple.com/bugs/X/ISO%209660/2831205.html

Secondly, here is some info from Chris Sarcone at Apple that he sent me:

> Has there been any work on CDROM-XA support in Darwin? The inability to
> mount
> CDROM-XA (mode-2 form-2) makes it impossible to play VideoCDs under OS
> X.x.x.

I believe this data is made available via the /dev/disk# node or
/dev/rdisk# node. You can issue read requests to it and it will return
data. It is best to read data in the optimal size for the node (you will
need to issue an ioctl to find this value). If you have a need to read
different sector sizes there is an additional ioctl to use for a
READ_CD-like command. See <IOKit/storage/IOCDMediaBSDClient.h>. There is
definitely a way to do this on OS X. The ISO9660 filesystem doesn't have
the greatest support for this yet, but hopefully can be extended in the
future*.

* The reason I say this is because VCDs tend to have an ISO 9660 track
and then tracks which are used for MPEG data and/or CDDA audio streams.
These tracks have different block sizes (ISO = 2k, MPEG = 2336
byte-blocks or something like that, CDDA = 2352 byte-blocks). It is a
lot of work for the filesystem to remap a "file" within the ISO
partition to a track with a different block size on another /dev entry.
Feel free to try doing this and send us a code diff though :).

-- Chris

------------------
6 Infinite Loop
M/S 306-2MS
Cupertino CA 95014
phone: (408) 974-4033
fax: (408) 862-7577
email: sarcone at apple.com



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