Patent ID: 7376184

Claim:
An encoder, comprising: a unit for segmenting a digitized video signal into blocks of a predetermined size; an intra mode encoding unit for creating an intra-field or an intra-frame as a reference image, in which motion-compensation prediction is not performed; a predictive mode encoding unit for performing motion-compensation prediction on another field or frame for encoding the difference from the reference image; and a selection unit for selecting one of the intra mode encoding unit and the predictive mode encoding unit for encoding a block constituting said another field or frame; wherein, in the case of selecting the intra mode encoding unit for encoding said block, the data encoded by the intra mode encoding unit and a signal indicating that said block is encoded by the intra mode encoding unit are transmitted; wherein for each signal the number of blocks encoded by intra encoding and predictive encoding is detected and a switch of the reference image is performed based on a comparison of the number of blocks of the intra encoding and predictive encoding with a threshold value.