8.0

P and B frames contain only differential information, these differences will be larger with time, since more
and more changes takes place from frame to frame. A large count does not make much sense, since
GOP has a maximum length of 15 (4P, 2B) in PAL and 18 (5P, 2B) in NTSC. (More than 2 B frames
between P frames is not allowed).
In a closed GOP
, B frames of the last subgroup may contain only backward predictions or references to the preceding P
frame, but no references to the following I frame, since it belongs to the next GOP.
I frames
Intra-frames: In these pictures, the entire image information of a frame is saved and only information from
this frame is used ("intra-frame encoded"). In contrast to the I frame, P and B frames save only the
differences between the current frame, and preceding and/or following frame are also found in MPEG
video (P frame = "predicted frame", B frame = "bidirectional frame", see Prediction
).
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