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Blu-ray Title Structure
The Blu-ray specification organizes a disc according to titles and playlists. The top level
structure is a title: when you start playing a disc, you play a title, That title can select another
title. Within a title, there are playlists. A playlist is a sequential list of A/V clips that are played
together as a unit. If you have done HD-DVD development, the Blu-ray terminology might
be confusing at first, because HD-DVD used these words to refer to different concepts: An
HD-DVD "playlist" is roughly equivalent to a BD title, and and HD-DVD "title" is roughly equivalent
to a BD playlist.
At the top level of the BD disc structure in the BDMV directory, there is a file called index.bdmv.
The structure of this
file is specified in the BD spec part 3.1, notably in section 5.2.3.3. Reading this, you'll find that
every BD disc is forced to have at least two titles, the "first play" title and the "top menu" title. The
first play title is what's played when the disc is first inserted, and the top menu title is what gets
played when the "top menu" button on the remote control is pressed (unless you've masked out
that user operation). This default behavior makes the "top menu" key behave a bit like a "reset"
button - you re-launch the disc, using the top menu title.
If you want to make a disc using BD-J, a reasonable choice is to make that disc have three titles
on it, as follows:
- A first play title (title_number = -1), which is an HDMV title that immediately selects title_number 1
- A top menu title (title_number = 0), which is an HDMV title that immediately selects title_number 1
- A normal title (with title_number = 1), which is a BD-J title that does what you want.
When you read 5.2.3.3, note the distinction between title_number and title_id.
Within the structure outlined above, any title bound xlets will be destroyed and re-launched if the top menu
button is pressed. Of course, you don't need to use HDMV for these two titles.
it's possible to use a BD-J title for the first play title and the
top menu title, but usually you want these titles to be very simple, perhaps presenting an FBI
warning card and immediately selecting the real title. Using movie mode for these simple tasks
probably results in a quicker disc start-up.
The code for an HDMV title is contained in the file MovieObject.bdmv, which is also in the disc's
BDMV directory. MovieObject.bdmv contains both the application lifecycle information, and the
HDMV "code" itself. In other words, MovieObject.bdmv is the file used for HDMV titles that fulfills the role that
is handled in BD-J by the combination of the BDJO file and the JAR files that make up the applications.
The syntax of the MovieObject.bdmv file is given in the BD specification part 3.1, section
10.3.2.2.
In the HD cookbook open-source project, a tool to make the index.bdmv file is under development,
and is called "index" (as of this writing, in the directory tools/index). A tool to create a minimal
MovieObject.bdmv file may be developed in the future, but the disc image available with the
cookbook project contains a MovieObject.bdmv containing an HDMV application that selects
title 1.
-- Main.billf - 17 Jun 2008
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