Question on Disc Type field value in MMC4

Takaharu Ai ai.takaharu at
Thu Dec 11 02:46:33 PST 2003

* From the T10 Reflector (t10 at, posted by:
* Takaharu Ai <ai.takaharu at>
Hello, MMC members and Mt.Fuji members,

I have one question about Disc Type field value for DVD media.

In MMC-3, the value of this field for DVD media was not clearly defined.
The document said;
  "If a field or bit is not applicable to the installed medium, the
   default parameters in the Write Parameters Page shall be returned in
   the corresponding field."
for Disc Information Block of READ DISC INFORMATION command.
In Write Parameter page, Disc Type field was not defined, but the
definition of Session Format field in the page was same as Disc Type. So
I think, the appropriate Disc Type field value for non CD/DDCD disc is 00h
as Session Format field is defined.

Also in Mt.Fuji5 Rev1.5, it is clearly defined that the inapplicable
fields in Disc Information Block shall be set to zero for non-CD disc.

But MMC4 has the following definition;
  "For all other media types, this field shall contain FFh."

I am very concerned that this MMC-4 definition makes inconsistency
between MMC-3 compliant devices and MMC-4 compliant devices.

Takaharu Ai
Panasonic AVC Networks Company
Osaka, Japan

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