IMAGE ENCODER AND IMAGE DECODER, IMAGE ENCODING METHOD AND IMAGE DECODING METHOD, IMAGE ENCODING PROGRAM AND IMAGE DECODING PROGRAM, AND COMPUTER READABLE RECORDING MEDIUM RECORDED WITH IMAGE ENCODING PROGRAM AND COMPUTER READABLE RECORDING MEDIUM RECORDED WITH IMAGE DECODING PROGRAM

• US 20080130747A1
• Filed: 10/31/2007
• Published: 06/05/2008
• Est. Priority Date: 07/22/2005
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Sugimoto, Kazuo, Yamada, Yoshihisa, Sekiguchi, Shunichi, Murakami, Tokumichi, Idehara, Yuichi, Asai, Koutarou, MORIYA, Yoshimi
• Granted Patent: US 8,488,889 B2
• Time in Patent Office: Days
• US Class Current: 375/240.15
• CPC Class Codes: H04N 19/107 between spatial and temporal predictive coding, e.g. picture refresh
• CPC Class Codes: H04N 19/109 among a plurality of temporal predictive coding modes
• CPC Class Codes: H04N 19/11 among a plurality of spatial predictive coding modes
• CPC Class Codes: H04N 19/119 Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/187 the unit being a scalable video layer
• CPC Class Codes: H04N 19/19 using optimisation based on Lagrange multipliers
• CPC Class Codes: H04N 19/52 by predictive encoding
• CPC Class Codes: H04N 19/56 Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques

Abstract

An image encoder including: a predicted-image generating unit that generates a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating methods; a prediction-mode judging unit that evaluates prediction efficiency of a predicted image outputted from the predicted-image generating unit to judge a predetermined prediction mode; and an encoding unit that subjects an output of the prediction-mode judging unit to variable-length encoding. The prediction-mode judging unit judges, on the basis of a predetermined control signal, which one of a common prediction mode and a separate prediction mode is used for respective color components forming the input image signal, and multiplexes information on the control signal on a bit stream, multiplexes, when the common prediction mode is used, common prediction mode information on the bit stream, and multiplexes, when the common prediction mode is not used, prediction mode information for each of the color components on the bit stream.

Claims

1. An image decoder that decodes a color image signal based on an input of a bit stream generated by compression-encoding a color image which is formed of a plurality of color components, the color image being compression-encoded in units of regions obtained by dividing the color image into predetermined regions, the image decoder comprising:

a header analyzing unit that extracts common encoding/independent encoding identification information from the bit stream;

a decoding unit that decodes, for each of the regions, an inter-prediction mode, a motion vector, and a reference image number included in the bit stream, and decodes a prediction error signal of each of the regions;

a predicted-image generating unit that generates a predicted image on the basis of the inter-prediction mode, the motion vector, and the reference image number which have been decoded; and

an adding unit that generates a decoded image by adding the decoded prediction error signal and the predicted image, wherein

the decoding unit decodes the inter-prediction mode, the motion vector, and the reference image number which are commonly used for all the color components, in a case where the common encoding/independent encoding identification information indicates that the regions serving as the units of encoding are encoded by a common prediction method for respective color components, and decodes the inter-prediction mode, the motion vector, and the reference image number in units of the regions for respective color components, in a case where the common encoding/independent encoding identification information indicates that the regions serving as the units of encoding are respectively encoded by a separate prediction method for respective color components, and

the predicted-image generating unit generates a predicted image by using the inter-prediction mode, the motion vector, and the reference image number which have been decoded, for respective color components.

2. An image encoder, comprising:

a predicted-image generating unit that generates a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating methods;

a prediction-mode judging unit that evaluates prediction efficiency of a predicted image outputted from the predicted-image generating unit to judge a predetermined prediction mode; and

a prediction-mode encoding unit that subjects an output of the prediction-mode judging unit to variable-length encoding, wherein

the prediction-mode judging unit separately performs judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object, and

the prediction-mode encoding unit refers to a lookup table obtained by tabulating combinations of states of a plurality of pieces of prediction mode information near the image region on an identical color component and predicted values for prediction modes of an encoding object to uniquely set a predicted value of prediction mode information from the states of the plurality of pieces of prediction mode information near the image region and perform encoding.

3. The image encoder according to claim 2, wherein the prediction-mode encoding unit dynamically updates values of predicted values of prediction mode information in the lookup table on the basis of the states of the plurality of pieces of prediction mode information near the image region on the identical color component and the values of the prediction modes of the encoding object.

4. An image encoder, comprising:

a predicted-image generating unit that generates a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating methods;

a prediction-mode judging unit that evaluates prediction efficiency of a predicted image outputted from the predicted-image generating unit to judge a predetermined prediction mode; and

a prediction-mode encoding unit that subjects an output of the prediction-mode judging unit to variable-length encoding, wherein

the prediction-mode judging unit separately performs judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object, and

the prediction-mode encoding unit changes a value of a prediction mode of an encoding object to a binary sequence and, in encoding respective bins of the binary sequence, performs arithmetic encoding while dynamically changing an occurrence probability according to a context set according to states of a plurality of pieces of prediction mode information near the image region on an identical color component.

5. The image encoder according to claim 4, wherein the prediction-mode encoding unit uses, as the context set according to the states of the plurality of pieces of prediction information near the image region on the identical color component, a state indicating into which of prediction in an image surface vertical direction and prediction in an image surface horizontal direction a prediction mode is classified.

6. The image encoder according to claim 4, wherein the prediction-mode encoding unit uses, as the context set according to the states of the plurality of pieces of prediction information near the image region on the identical color component, a state indicating which of DC prediction and prediction other than the DC prediction is used as a prediction mode.

7. An image encoding method, comprising the steps of:

generating a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating methods;

evaluating prediction efficiency of the generated predicted image to judge a predetermined prediction mode and separately performing judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object; and

subjecting an output in the step of performing judgment of a prediction mode to variable-length encoding and referring to a lookup table obtained by tabulating combinations of states of a plurality of pieces of prediction mode information near the image region on an identical color component and predicted values for prediction modes of an encoding object to uniquely set a predicted value of prediction mode information from the states of the plurality of pieces of prediction mode information near the image region and perform encoding.

8. An image encoding program for causing a computer to execute the steps of:

generating a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating methods;

evaluating prediction efficiency of the generated predicted image to judge a predetermined prediction mode and separately performing judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object; and

subjecting an output in the step of performing judgment of a prediction mode to variable-length encoding and referring to a lookup table obtained by tabulating combinations of states of a plurality of pieces of prediction mode information near the image region on an identical color component and predicted values for prediction modes of an encoding object to uniquely set a predicted value of prediction mode information from the states of the plurality of pieces of prediction mode information near the image region and perform encoding.

9. A computer-readable recording medium recorded with an image encoding program for causing a computer to execute the steps of:

generating a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating methods;

evaluating prediction efficiency of the generated predicted image to judge a predetermined prediction mode and separately performing judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object; and

subjecting an output in the step of performing judgment of a prediction mode to variable-length encoding and referring to a lookup table obtained by tabulating combinations of states of a plurality of pieces of prediction mode information near the image region on an identical color component and predicted values for prediction modes of an encoding object to uniquely set a predicted value of prediction mode information from the states of the plurality of pieces of prediction mode information near the image region and perform encoding.

10. An image encoding method, comprising the steps of:

generating a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating method;

evaluating prediction efficiency of the generated predicted image to judge a predetermined prediction mode and separately performing judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object; and

subjecting an output in the step of performing judgment of the prediction mode, changing a value of a prediction mode of an encoding object to a binary sequence and, in encoding respective bins of the binary sequence, performing arithmetic encoding while dynamically changing an occurrence probability according to a context set according to states of a plurality of pieces of prediction mode information near the image region on an identical color component.

11. An image encoding program, for causing a computer to execute the steps of:

generating a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating method;

evaluating prediction efficiency of the generated predicted image to judge a predetermined prediction mode and separately performing judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object; and

subjecting an output in the step of performing judgment of the prediction mode, changing a value of a prediction mode of an encoding object to a binary sequence and, in encoding respective bins of the binary sequence, performing arithmetic encoding while dynamically changing an occurrence probability according to a context set according to states of a plurality of pieces of prediction mode information near the image region on an identical color component.

12. A computer readable recording medium recorded with an image encoding program for causing a computer to execute the steps of:

generating a predicted image in accordance with a plurality of prediction modes indicating predicted-image generating method;

evaluating prediction efficiency of the generated predicted image to judge a predetermined prediction mode and separately performing judgment of a prediction mode for each of color components with respect to a unit of an image region of a prediction object;

subjecting an output in the step of performing judgment of the prediction mode, changing a value of a prediction mode of an encoding object to a binary sequence and, in encoding respective bins of the binary sequence, performing arithmetic encoding while dynamically changing an occurrence probability according to a context set according to states of a plurality of pieces of prediction mode information near the image region on an identical color component.