Blocks length selection method based on adaptive threshold and typical sample predication

The invention relates to a method for selecting length of block, especially a method for selecting length of block based on threshold value of self-adaptation and prediction of typical sample used incompression of audio frequency signal. The method removes noise of pre-echo totally meanwhile gains high coding efficiency with small calculating operations. Two measuring criterions about detection of jump signal are proposed. The proposed 'masking off analytical method of local maximum' can avoid block with shorter length to be overspent so as to optimize performance of speed rate-distortion ofencode. The invention brings up to scheme of fast arithmetic operation based on mechanism of sub-sample.