Picture Types

The MPEG standard specifies four picture types which differ regarding compression efficiency and access behaviour:

I-Pictures - Intra Coded Pictures

I-pictures are completely coded and does not refer to preceding or succeeding pictures.

P-Pictures - Predictive Coded Pictures

The picture's contents is derived from a preceding picture, changes are coded by its difference in combination with motion compensation. P-pictures can only be represented, if the original pictures are still accessible.

B-Pictures - Bidrectionally Coded Pictures

B-pictures will be derived from both a preceding and a succeeding picture. In principle they represent an interpolation between two pictures.

D-Pictures - DC Coded Pictures

D-pictures contain the entire contents like I-pictures, but are massively compressed. They are intended for fast-forward functions.

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