DC Coded Pictures

DC pictures serve for fast-forward functions. They must be decoded with high speed without access to preceding and/or following pictures. Therefore they are coded like I-pictures but contain only a very small amount of information.

Only the so-called DC values are regarded, which result from the DCT. These are the basic values for brightness and colour of a picture segment. Any further details of these segments are rejected.

In principle the resolution is reduced in relation to a completely coded picture by the factor 8 in both directions. The denotation is derived from the abbreviation for direct current, because it describes the basic or constant colour of the segment. The varying components are denoted accordingly with AC (alternating current).

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