Twin Format layer to play selection issue for PC software player

keiji_katata at keiji_katata at
Thu Aug 11 05:30:50 PDT 2005

* From the T10 Reflector (t10 at, posted by:
* keiji_katata at

Hi Henry,

This is my technical consideration simply. My opinion is not decided any
(agree or opposite).

1. This is only correct for the current proposal, but not for the Microsoft

A proposal may need to cover the original main purpose of Twin Format layer
disc. Otherwise the proposal could be miner one.

2. However, this is definitely not the case.

If user do not know what it is, how can you reduce the telephone call from
such user? The user may talk about non Windows OS system, but calls to
I agree some additional help than the disc label may help the user. But
some user may have DVD only system. Some user may have HD-DVD only system.
It may not work in some cases.

3. Please allow me to address this directly later.

You may need to explain the feasibility. At the disc mount time, Windows XP
and Mac OS check (search) the contents on the disc. It may take very long
time, then user may confuse.

4. extremely problematic for Windows

It may not be problem. I can add a shell extension to Explorer. I see that
some software show the physical interface of the external drive by ICON.
For example, the interface Icon shows the used interface e.g. USB, 1394,
PCMCIA or other. User may use the menu of the shell extension to switch the
Format layer.

5. new drives are often installed on legacy OS

Blue drive may not work well with old OS like Win98/ME, Mac OS9 and so on.
But WinXP, MacOS X may be OK using some additional software. Anyway UDF
2.5/2.6 is necessary for Blue media. So we may not need to talk about such
old OS. Because the system cannot mount the disc.

6. support notion of "multisession" for HD-DVD layer

Well.. I believe that DVD-ROM, HD-DVD ROM and BD-ROM do not have any idea
of "multisession". So this is significant change of their Part 1
specifications. Also UDF specification change is necessary.

7. There is no violation of OSTA UDF

Well.. The 1st session does not have metadata partition. The 2nd session
has metadata partition. ??

* Playback software will never have random access to two layers.

Explorer is included in such software? When your mouse cursor stays on an
ICON, pop up information of the object is shown. The root directory of the
1st session will have many objects. The root directory of the 2nd session
will have many too. They are sorted by name, then user may think that those
objects are on a disc. Then user press Find button.....


HD Video - CD audio scenario is like this.
You have HD Video system in your living room. HD system mounts HD-CD disc
as a HD disc. You enjoy the HD video.
Your family has CD player on the wall of kitchen. Your family enjoy the
sound tracks of the HD video of the HD-CD disc in kitchen.
You are reading a book in your living room. Your HD system had mounted the
HD-CD disc as HD disc. But you have changed it to CD playback. The HD
system turns off the TV monitor power. So you are reading the book in your
living room.

Best regards,

Keiji Katata

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