Image encoding method and image encoder, image decoding method and image decoder, and image processing system

Abstract

A method and an apparatus improving the coding efficiency by representing encoded data in a compact form by means of a pattern matching technique. A waveform vector similar to a partial signal waveform of an image signal in a predetermined group of waveform vectors is searched for. When a compression encoding is performed for information to identify the waveform vector searched for, similarity information, and a position in an image signal of the partial signal waveform in accordance with a predetermined encoding rule, the position in the image signal of the partial signal waveform is encoded through replacement with position information in a predetermined partial domain of the image signal. As a result; since the position in the image of the partial signal waveform that is the most similar to the waveform vector is encoded through replacement with the position information in the predetermined partial domain of the image signal, it is possible to represent the position more compactly.

1 . An image encoding method, comprising: 
 a first image encoding step performing a compression encoding for a first image signal per predetermined partial domain in accordance with a first encoding rule; and    a second image encoding step performing a compression encoding for a second image signal per partial signal waveform of the second image signal in accordance with a second encoding rule,    wherein a signal corresponding to an error signal between a first image signal provided to the first encoding step and a signal obtained by performing a local decoding process for encoding information obtained at the first image encoding step is set as a second image signal provided to the second image encoding step, and wherein the second image encoding step comprises a pattern matching step searching for a waveform vector in a predetermined group of waveform vectors based upon inner products of the waveform vectors and a partial signal waveform of the second image signal; and a waveform pattern encoding step performing a compression encoding for information to identify the waveform vector searched for, an inner product value of the partial signal waveform and the waveform vector searched for, and a position in the second image of the partial signal waveform in accordance with the second encoding rule, wherein in a process in which the pattern matching step and the waveform pattern encoding step are iterated until a predetermined condition is satisfied, whenever encoding information is obtained at the waveform pattern encoding step, a reconstructed waveform of a partial signal waveform obtained from the encoding information is subtracted from the second image signal so as to produce a second image signal to be provided to the pattern matching step, and the second image signal is encoded according to the encoding information obtained at the waveform pattern step until the predetermined condition is satisfied, and wherein the position in the image of the partial signal waveform is encoded through replacement with position information in a predetermined partial domain of the image signal and in the pattern matching step, a group of waveform vectors to be used is selected among a plurality of groups of waveform vectors based on a parameter used to perform the compression encoding at the first image encoding step and the position in the second image of the partial waveform signal.    
   
   
       2 . The image encoding method as claimed in  claim 1 , wherein the first image signal to be provided to the first image encoding step becomes information representing a source image to be encoded, and the second image signal to be provided to the second image encoding step becomes an encoding distortion signal generated by encoding the source image at the first image encoding step.  
   
   
       3 . The image encoding method as claimed in  claim 2 , wherein the second image signal becomes information representing a prediction residual image obtained by performing a motion compensation prediction for the error signal.  
   
   
       4 . The image encoding method as claimed in  claim 3 , wherein at the second image encoding step, when the information representing the prediction residual image is obtained, motion information detected in an encoding process for a source image at the first image encoding step is used to perform the motion compensation prediction.  
   
   
       5 . The image encoding method as claimed in  claim 3 , wherein at the second image encoding step, the motion information detected in an encoding process for a source image at the first image encoding step is set as an initial value, motion information is detected in positions adjacent to a position where a motion regarding the initial value has occurred, and the motion information is used to perform the motion compensation prediction.  
   
   
       6 . An image encoder, comprising: 
 a first image encoding part performing a compression encoding for a first image signal per predetermined partial domain in accordance with a first encoding rule; and    a second image encoding part performing a compression encoding for a second image signal per partial signal waveform of the second image signal in accordance with a second encoding rule,    wherein a signal corresponding to an error signal between a first image signal provided to the first encoding part and a signal obtained by performing a local decoding process for encoding information obtained by the first image encoding part is set as a second image signal provided to the second image encoding part, and wherein the second image encoding part comprises a pattern matching part searching for a waveform vector in a predetermined group of waveform vectors based upon inner products of the waveform vectors and a partial signal waveform of the second image signal; and a waveform pattern encoding part performing a compression encoding for information to identify the waveform vector searched for, an inner product value of the partial signal waveform and the waveform vector searched for, and a position in the second image of the partial signal waveform in accordance with the second encoding rule, wherein in a process in which operations on the pattern matching part and the waveform pattern encoding part are iterated until a predetermined condition is satisfied, whenever encoding information is obtained by the waveform pattern encoding part, a reconstructed waveform of a partial signal waveform obtained from the encoding information is subtracted from the second image signal so as to produce a second image signal to be provided to the pattern matching part, and the second image signal is encoded according to the encoding information obtained by the waveform pattern part until the predetermined condition is satisfied, and wherein the pattern matching part comprises a plurality of groups of waveform vectors; and a waveform vector group selection part selecting a group of waveform vectors to be used among the groups of waveform vectors based upon a parameter used by the first image encoding part to perform the compression encoding and the position in the second image of the partial waveform signal.    
   
   
       7 . The image encoder as claimed in  claim 6 , wherein the first image signal to be provided to the first image encoding part becomes information representing a source image to be encoded, and the second image signal to be provided to the second image encoding part becomes an encoding distortion signal generated by encoding the source image at the first image encoding part.  
   
   
       8 . The image encoder as claimed in  claim 7 , wherein the second image signal becomes information representing a prediction residual image obtained by performing a motion compensation prediction for the error signal.  
   
   
       9 . The image encoder as claimed in  claim 8 , wherein when the information representing prediction residual image is obtained, the second image encoding part uses motion information detected in an encoding process for a source image at the first image encoding part to perform the motion compensation prediction.  
   
   
       10 . The image encoder as claimed in  claim 9 , wherein the second image encoding part sets the motion information detected in an encoding process for a source image at the first image encoding part as an initial value, detects motion information in positions adjacent to a position where a motion regarding the initial value has occurred, and uses the motion information to perform the motion compensation prediction.  
   
   
       11 . An image processing system, comprising: 
 an image encoder having a first image encoding part performing a compression encoding for a first image signal per predetermined partial domain in accordance with a first encoding rule; and a second image encoding part performing a compression encoding for a second image signal per partial signal waveform of the second image signal in accordance with a second encoding rule, wherein a signal corresponding to an error signal between the first image signal provided to the first encoding part and a signal obtained by performing a local decoding process for encoding information obtained by the first image encoding part is set as the second image signal provided to the second image encoding part, and wherein the second image encoding part comprises: a pattern matching part searching for a waveform vector in a predetermined group of waveform vectors based upon inner products of the waveform vectors and a partial signal waveform of the second image signal; and a waveform pattern encoding part performing a compression encoding for information to identify the waveform vector searched for, an inner product value of the partial signal waveform and the waveform vector searched for, and a position in the second image of the partial signal waveform in accordance with the second encoding rule, wherein in a process in which operations on the pattern matching part and the waveform pattern encoding part are iterated until a predetermined condition is satisfied, whenever encoding information is obtained at the waveform pattern encoding part, a reconstructed waveform of a partial signal waveform obtained from the encoding information is subtracted from the second image signal so as to produce a second image signal to be provided to the pattern matching part, and the second image signal is encoded according to the encoding information obtained at the waveform pattern part until the predetermined condition is satisfied, and wherein the pattern matching part comprises: a plurality of groups of waveform vectors; and a waveform vector group selection part selecting a group of waveform vectors to be used among the groups of waveform vectors based upon a parameter for the encoding at the first image encoding part and the position in the second image of the partial waveform signal; and    an image decoder comprising: a first image decoding part receiving a first compressed image and reconstructing first image information by decompressing the first compressed image information per predetermined partial domain; a second image decoding part receiving a second compressed image and reconstructing second image information by decompressing the second compressed image information per predetermined partial signal waveform; and an image synthesizing part obtaining output image information by synthesizing the first image information and the second image information, wherein the second image decoding part comprises: a plurality of predetermined groups of waveform vectors; a first part decoding the second compressed image information in accordance with a predetermined decoding rule and obtaining information to identify a waveform vector, an inner product value of a partial signal waveform and the waveform vector and a position in an image of the partial signal waveform; a second part selecting a group of waveform vectors to be used among a plurality of predetermined groups of waveform vectors based upon a code parameter included in the first compressed image information provided to the first image decoding part and the position in the image of the partial waveform signal; and a third part generating the second image information based upon the waveform vector identified by the information to identify the waveform vector in the selected group of waveform vectors, the inner product value, and the position in the image of the partial signal waveform.