Coding and decoding

Claim 2

A coding method as claimed in claim 1, the method further comprising a step for combining the determined mode data at said mode determining step and the calculated displacement data at said displacement calculating step into a data pack.

Claim 3

A coding method as claimed in claim 1 or 2, wherein said search area determining step determines the search area which is composed of blocks being closely adjacent to a present block among previously coded blocks in frame data.

Claim 4

A coding method as claimed in claim 1, 2 or 3, wherein said mode determining step comprises the sub-steps of: comparing energy levels between said present block data and said differential data; determining a first mode when the energy level of said present block data is lower than that of said differential data; and determining a second mode when the energy level of said differential data is lower than that of said block data for coding.

Claim 5

A coding method as claimed in claim 4, wherein said coding step codes said present block data for coding in the case that said first mode is determined at said mode determining step, and codes said differential data in the case that said second mode is determined at said mode determining step.

Claim 6

A coding method as claimed in claim 4 or 5, wherein said step for reconstructing said frame data reconstructs the frame data by storing blocks sequentially when said first mode is determined at said mode determining step, or by storing data obtained by adding said differential data and said similar pattern block data when said second mode is determined at said mode determining step.

Claim 7

In a method for decoding data coded with block DPCM in a still image or active image in an intra frame mode, a decoding method comprising the steps of: receiving transmitted data coded by a method according to any of the preceding claims; decoding said transmitted data to data of the spacial domain; separating said transmitted coded data into mode data and displacement data; reading the block data corresponding to said displacement data from the frame data obtained by a predetermined reconstructing step; and reconstructing said frame data by sequentially storing the block data obtained from calculation of said decoded transmitted data and said read block data according to the mode of said mode data.

Claim 8

A decoding method as claimed in claim 7, wherein, in said step for separating said mode data, predetermined first mode data are output when said transmitted data are coded data of a block, and predetermined second mode data are output when said reconstructed data are differential data between a present block and a similar pattern block.

Claim 9

A decoding method as claimed in claim 8, wherein, in a step for calculation according to said mode data, said decoded transmitted data are output when said mode data is said first mode and said decoded transmitted data and the block data read from said frame data are added and output when said mode data is said second mode.

Claim 10

In a coder for dividing a frame into a plurality of blocks and coding data of the blocks, with coding of a still image or an active image in an intra frame mode, a coder comprising: a memory for storing data in units of blocks, thereby reconstructing frame data; means for determining a predetermined search area in said frame data; means for receiving present block data to be coded, estimating a most similar pattern block with a present block from said search area, and calculating a displacement obtained by said estimation; a displacement compensation means for reading data of said similar pattern block data from said memory according to the displacement supplied from said displacement estimation means; means for calculating differential data between said present block data for coding and the block data output from said displacement compensation means; means for determining a mode of transmitting data by comparing said present block data with said differential data, and outputting the determined mode data; means for selecting one of said present block data and said differential data according to the mode data from said mode determining means, and coding the selected one; means for reconstructing data output from said coder into an original state before coding; and an adder for supplying the output data from said reconstructing means, or the data which add the output data from said reconstructing means and the output data from said displacement compensation means, to said memory in accordance with the mode determined by said mode determining means.

Claim 11

A coder as claimed in claim 10, wherein said search area determining means determines a search area which is composed of blocks adjacent to a present block among previously coded blocks in the frame data which are stored in said memory as a search area.

Claim 12

A coder as claimed in claim 10 or 11, wherein said mode determining means comprises: means for comparing the energy level of said present block data for coding with that of said differential data; means for outputting predetermined first mode data in the case that the energy level of said present block data is lower than that of said differential data, and predetermined second mode data in the case that the energy level of differential data is lower than that of present block data, as determined by said comparing means.

Claim 13

A coder as claimed in claim 10, 11 or 12, further comprising an adder at which said present block data coding are applied to an input terminal and an output terminal is connected to an input terminal of said coding means; and a first switch which is turned on or off according to the output signal of said mode determining means, of which one terminal is connected to the output terminal of said displacement compensation means, and the other is connected to another input terminal of said adder.

Claim 14

A coder as claimed in claims 12 and 13, wherein said first switch is turned off when the output signal of said mode determining means is the first mode data, and turned on when it is the second mode data.

Claim 15

A coder as claimed in any of claims 10 to 14, further comprising a second switch which is turned on or off according to the output signal of said mode determining means, of which one terminal is connected to the output terminal of said displacement compensation means, and the other is connected to an input terminal of said adder.

Claim 16

A coder as claimed in claims 12 and 15, wherein said second switch is turned off when the output signal of said mode determining means is the first mode data, and turned on when it is the second mode data.

Claim 17

A coder as claimed in any of claims 10 to 16, the device further comprising a mode-displacement data combiner which combines the mode data output from said mode determining means with displacement data output from said displacement estimation means and sends mode-displacement data to a transmission channel.

Claim 18

In a device for decoding data coded by block DPCM with a still image or active image in an intra frame mode, a decoder comprising: an input terminal for receiving data coded by a coder according to any of claims 10 to 17; means for reconstructing the data applied from said input terminal to data of the spacial domain; means for separating transmitting data of the coder into mode data and displacement data, and outputting the same; a memory for storing previously decoded block data in a regular sequence and reconstructing the frame data; a displacement compensation means for reading the block data corresponding to said displacement data from the frame data of said memory; and an adder for selectively adding the output data from said displacement compensation means, to the output data of said reconstructing means according to said mode data, and outputting the same to said memory.

Claim 19

A decoder as claimed in claim 18, wherein said mode-displacement data separator outputs predetermined first mode data when said reconstructed data are obtained from data which code a block in said coder, and predetermined second mode data when said reconstructed data are obtained from differential data between block data and data of a block with a most similar pattern.

Claim 20

A decoder as claimed in claim 18 or 19, further comprising a switch which is turned on or off according to said mode data, of which one terminal is connected to an output terminal of said displacement compensation means and the other is connected to an input terminal of said adder.

Claim 21

A decoder as claimed in claims 19 and 20, wherein said switch is turned off when an output signal of said mode-displacement separator is the first mode data, and turned on when it is the second mode data.