BCA Read

Bmcferrin at aol.com Bmcferrin at aol.com
Wed Sep 24 10:24:50 PDT 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* Bmcferrin at aol.com
*

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Members:
I started this discussion, so I must add a few words.

Research shows the following:
Fuji1, format=3 (BCA) seems to be optional, but the wording is
confusing.
Fuji2, format=3 (BCA) is mandatory.
Fuji3, format=3 (BCA) is mandatory.
Fuji4, format=3 (BCA) is mandatory.
Fuji5, format=3 (BCA) is mandatory.
MMC2 mandatory not specified.
MMC3 mandatory not specified.
MMC4 (since rev 2c), format=3 (BCA) is mandatory.

In the case of MMC3, I cannot escape responsibility for any confusion.
MMC2 and MMC3 only cause a question: When a command is required with
respect to some feature, but we have not identified specific parts that
are to be mandatory, how is an implementer to know which parts are
mandatory?  Since it is not specified, is our answer: none or all?  It
cannot be none, because that would make too many commands into no-ops.
In the case of READ DVD STRUCTURE, it cannot be all, because drives
cannot support "all" with all media.  We could suggest that the format
codes supported should be all that are associated with supported DVD
media types.  In that case, BCA Read is mandatory for DVD-ROM and
DVD-Video.

The above does not solve Henry's problem.  Confusion from past standards
has presented him with drives that should, but do not support BCA Read.
We could tell Henry: those devices are not compliant with the standard;
we are very sorry.

Bill



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Members:
 I started this discussion, so I must add a few words.
 
Research shows the following:
 Fuji1, format=3D3 (BCA) seems to be optional, but the wording is = confusing.
 Fuji2, format=3D3 (BCA) is mandatory.
 Fuji3, format=3D3 (BCA) is mandatory.
 Fuji4, format=3D3 (BCA) is mandatory.
 Fuji5, format=3D3 (BCA) is mandatory.
 MMC2 mandatory not specified.
 MMC3 mandatory not specified.
 MMC4 (since rev 2c), format=3D3 (BCA) is mandatory.
 
In the case of MMC3, I cannot escape responsibility for any = confusion.  MMC2 and MMC3 only cause a question: When a command is = required with respect to some feature, but we have not identified = specific parts that are to be mandatory, how is an implementer to know = which parts are mandatory?  Since it is not specified, is our = answer: none or all?  It cannot be none, because that would make = too many commands into no-ops.  In the case of READ DVD STRUCTURE, = it cannot be all, because drives cannot support "all" with all = media.  We could suggest that the format codes supported should be = all that are associated with supported DVD media types.  In that = case, BCA Read is mandatory for DVD-ROM and DVD-Video.
 
The above does not solve Henry's problem.  Confusion from past = standards has presented him with drives that should, but do not support = BCA Read.  We could tell Henry: those devices are not compliant = with the standard; we are very sorry.
 
Bill
 

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