vcdimager: Segment Items
1.6.2 Segment Items
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Segment items are stored in the so-called SPI area, which consists of up
to 1980 allocation units which are called "segments". Each segment
consists of 150 XA form 2 sectors. Thus the SPI area can contain up to
658 MB of real-time data(1).
A segment (play) item is a MPEG stream stored in one or more
consecutive segments. A segment item can be
* MPEG video with _optional_ MPEG audio.
* MPEG encoded still pictures with _optional_ MPEG audio.
* MPEG audio only.(2)
Advantages
..........
* Up to 1980 segment items possible.
* Still pictures and audio only MPEG streams allowed.
* No pre-gaps.
Disadvantages
.............
* Only accessible through PBC.
* Segment item size limited by SPI area size.
* Segment item size is fixed to 150 sectors (the same as the gap
between tracks) which may be wasteful of space. If you have a
large number of small motion videos, it might be advantageous to
combine them into a track and use entry points into the track.
"Continued" segments allow for logical segments (something you
refer to as a segment in authoring) to be larger than 150 segments.
However breaking a logical segments up into many small physical
segments is not as clean as having one physical unit for one
logical unit. And there may be additional fragmentation in the
form of internal sector padding.
---------- Footnotes ----------
(1) 1980 * 150 * 2324 = 690228000 bytes
(2) Which allows for several hours of audio only play back to fit on
a CD-ROM.
Info Catalog
vcdimager: Sequence Items
vcdimager: Play Items