Editing Inter frame (section)

==Typical Group Of Pictures (GOP) structure==
[[File:IBBPBB_inter_frame_group_of_pictures.svg|thumb|350px|Illustration of dependencies of the group of pictures scheme IBBPBB... Time goes from left to right.]]
The typical [[Group of pictures]] (GOP) structure is IBBPBBP... The I-frame is used to predict the first P-frame and these two frames are also used to predict the first and the second B-frames. The second P-frame is predicted also using the first I-frame. Both P-frames join to predict the third and fourth B-frames. The scheme is shown in the next picture:

This structure suggests a problem because the fourth frame (a P-frame) is needed in order to predict the second and the third (B-frames). So we need to transmit the P-frame before the B-frames and it will delay the transmission (it will be necessary to keep the P-frame).
<!-- [[Image:IPB images sequence.png|thumb|350px|Example of a GOP structure]] -->
This structure has strong points:
* It minimizes the problem of possible uncovered areas.
* P-frames and B-frames need less data than I-frames, so less data is transmitted.

But it has weak points:
* It increases the complexity of the decoder, which can mean more memory needed to rearrange the frames, and a tiny bit more processing power.
* B-frames may introduce decoding dependency which inevitably increases decoding latency.