Presentation

Combinations of presentation types

Type	Count	Representation
Video	1 stream only	MPEG-1 or MPEG-2 Video
Audio	maximum of 8 streams	Linear PCM and/or: Dolby AC-3 (NTSC) MPEG audio (PAL)
Sub-picture	max 32 streams	Run-length encoded with bitmap of 2 bits/pixel

Presentation stream rates

max total of combined audio and video: 9.8 Mbit/sec max sum of Elementary streams + systems overhead: 10.08 Mbit/sec.

Presentation of PGC

The program chain (PGC) can be presented either serially (linear) or in random/shuffle (non-linear) fashion.

For example, a quiz title should break each question into separate programs. The next program chain branched to would be determined by the answered provided by the user.

Still image presentation

Still pictures are coded as MPEG intra frames. They may be displayed for indefinite duration. They can be accompanied by background music, or audio can be muted.

still function is created by the action of the navigation system
The same video frame and sub-picture is frozen (displayed over and over again on the TV) while audio is or playing in background.

There are three types of the Still Function:

Type	Timing	Still time in seconds
PGC Still	Stills at end of the PGC	0-254, limitless
Cell Still	Stills at end of the Cell	0-254, limitless
VOBU Still	Stills in every VOBU in the Cell	limitless

VOBU: Video Object Unit.

Location of each command

Within a program chain (PGC), commands can be located at the front of the chain, in between cells of the chain, and at the end of the chain.

                          Program chain

    [Pre-Commands] [Cell] [Cell] [Cell-Command] [Cell] [Post-Commands]

  Each cell can have one command.  There is a restriction that
  no more than 128 commands can be contained within a program chain:

       Pre-commands + Cell Commands + Post Commands <= 128

  Further, there are a maximum of 36 buttons, each of which can
  have one associated command.

Example of a PGC transition

[taken from the Hitachi overheads]

3 quiz problems are presented to the user. Each quiz problem/question is coded as a separate program chain. One of the questions prompts the user for a "Yes" or "No" answer.

The Link command is used to branch from the original top-level menu to one of the three program chains. The Set Command is used to tally a score. Finally, the CompareLink command (which consist of two commands, Compare & Link) branches to a particular Program depending on the user's answer.