Mpeg containers and streams, Mpeg-1 – Apple Final Cut Pro 7 User Manual
Page 1912
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).
: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
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.
MPEG-1
MPEG-1 is the earliest format specification in the family of MPEG formats. Because of its
low bit rate, MPEG-1 has been popular for online distribution and in formats such as Video
CD (VCD). DVDs can also store MPEG-1 video, though MPEG-2 is more commonly used.
Although the MPEG-1 standard actually allows high resolutions, almost all applications
use NTSC- or PAL-compatible image dimensions at quarter resolution or lower.
Common MPEG-1 formats include 320 x 240, 352 x 240 at 29.97 fps (NTSC), and 352 x 288
at 25 fps (PAL). Maximum data rates are often limited to around 1.5 Mbps. MPEG-1 only
supports progressive-scan video.
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Appendix B
Video Formats