Abstract: A novel method for detecting class errors in the image signal which has been transmitted in a compressed form by using a classified vector quantization technique comprises the steps of selecting reference blocks out of neighboring blocks of the current block; calculating an error detecting function using the class name for the current block and the reference blocks; and determining the error for the current block by comparing the calculated error detecting function with a predetermined threshold.

Abstract: In fingerprint pattern classification, radial scanning vectors are used. A space between two adjacent ridge lines including a core point is traced by radial scanning. Radial distribution of number of cross points from the core point is a clue to a fingerprint classification.

Abstract: A novel method for concealing or rectifying channel errors present in a decoded image signal which has been transmitted in a compressed form by using a classified vector quantization technique comprises a step for estimating the class for a current block by detecting boundary edges at each of four groups of neighboring pixels; and a step for estimating the representative vector for the current block by calculating a multiple number of side-matching functions and choosing the candidate vector producing the smallest side-matching function as the representative vector for the current block.