Apple Final Cut Pro 6 User Manual
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The same GOP pattern can produce different results when used with an open or closed
GOP. For example, a closed GOP would start an IBBP pattern with an I-frame, whereas
an open GOP with the same pattern might start with a B-frame. In this example,
starting with a B-frame is a little more efficient because starting with an I-frame means
that an extra P-frame must be added to the end (a GOP cannot end with a B-frame).
MPEG Containers and Streams
MPEG video and audio data are packaged into discrete data containers known as streams.
Keeping video and audio streams discrete makes it possible for playback applications to
easily switch between streams on the fly. For example, DVDs that use MPEG-2 video can
switch between multiple audio tracks and video angles as the DVD plays.
Each MPEG standard has variations, but in general, MPEG formats support two basic
kinds of streams:
 Elementary streams: These are individual video and audio data streams.
 System streams: These streams combine, or multiplex, video and audio elementary
streams together. They are also known as multiplexed streams. To play back these
streams, applications must be able to demultiplex the streams back into their
elementary streams. Some applications only have the ability to play elementary streams.
:06 :07 :08 :09
:09
:10 :11 :12 :13 :14 :15 :16 :17 :18 :19 :20 :21
:04 :05
Open GOP
(IBBP, 15 frames)
I B B P B B P B B P B B P B B I
B B
P
:03
:06 :07 :08
:10 :11 :12 :13 :14 :15 :16 :17 :18
:04 :05
Closed GOP
(IBBP, 15 frames)
P B B P B
P B
P B P
I B
B
B
B