MPEG GOP of 9
The larger the GOP, the greater the compression and propagation of errors.
Where Motion JPEG encoding fully encodes each frame of an image sequence, MPEG fully encodes some frames and partially encodes frames between these reference frames. The GOP (Group of Picture) represents the number of frames between reference frames ("I"). Due to the nature of MPEG encoding, any 2-3 pulldown in a program must have a consistent cadence from the top of the program, so the software knows which frames to use as reference frames. MPEG encoding is used in the production of DVDs and in the broadcast of HDTV signals.
Intracoded Frames: These "I-frames" are composed without reference to other frames. I-frames reduce spatial redundancy and achieve only a moderate compression.
Predictive coded frames: "P-frames" predict forward in the GOP.
Bidirectionally interpolated frames: "B-frames" predict forward and backward in the GOP. These frames are the most compressed.
The larger the GOP, the greater the compression and propagation of errors.
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Avid Technology,
Inc. for more technical info regarding Avid
products.
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Filmmaker's
Home Page/ Editing.
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Alan
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