Image coding method and apparatus using spatial predictive coding of chrominance and image decoding method and apparatus

• US 8,345,995 B2
• Filed: 08/06/2007
• Issued: 01/01/2013
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Chang-yeong, Kim, Woo-shik, Seo, Yang-seock
• Primary Examiner(s): Ahmed, Samir
• Application Number:
  US11/882,869
• Publication Number:
  US 20080025406A1
• Time in Patent Office: 1,975 Days
• Field of Search: None
• US Class Current: 382/236
• CPC Class Codes: G06T 9/004 Predictors, e.g. intraframe, interframe coding
• CPC Class Codes: G06T 9/005 Statistical coding, e.g. Huffman, run length coding
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/11 among a plurality of spatial predictive coding modes
• CPC Class Codes: H04N 19/122 Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/182 the unit being a pixel
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/44 Decoders specially adapted therefor, e.g. video decoders which are asymmetric with respect to the encoder
• CPC Class Codes: H04N 19/593 involving spatial prediction techniques
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

A method and apparatus for coding a chrominance component of an intra-image using spatial predictive coding and a method and apparatus for decoding the coded chrominance component are provided. The coding apparatus includes a variation calculator, which calculates a vertical variation and a horizontal variation with respect to a current block to be predictively coded among blocks having a predetermined size, into which a chrominance component of an input image is divided, using pixel values in an upper reference block adjacent to the current block and pixel values in a side reference block adjacent to the current block; a hybrid predictor, which divides the current block into a predetermined number of regions according to the vertical and horizontal variations and generates a prediction value of each pixel in each region using a pixel value in the upper reference block or a pixel value in the side reference block; a differential value generator, which generates a differential value between the prediction value and a corresponding real pixel value in the current block and codes the differential value using a predetermined coding method.

Claims

1. A coding method comprising:

(a) dividing pixels of a chrominance component of an input image into blocks having a predetermined size;

(b) dividing a current block to be predictively coded into a predetermined number of regions according to a predetermined number of prediction methods and generating prediction values of each pixel in the current block according to the respective prediction methods using a pixel value in an upper reference block adjacent to the current block and a pixel value in a side reference block adjacent to the current block;

(c) generating differential values between the prediction values corresponding to the respective prediction methods and a corresponding real pixel value in the current block; and

(d) selecting a differential value requiring a least number of bits for coding among the differential values and coding the selected differential value and information on a prediction method corresponding to the selected differential value using a predetermined coding method.

2. The coding method of claim 1, wherein step (b) comprises dividing the current block into an upper region and a lower region in a vertical direction, generating prediction values in the upper region using pixel values in the upper reference block, and generating prediction values in the lower region using pixel values in the side reference block.

3. The coding method of claim 1, wherein step (b) comprises dividing the current block into a first region and a second region in a horizontal direction, generating prediction values in the first region adjacent to the side reference block using pixel values in the side reference block, and generating prediction values in the second region using pixel values in the upper reference block.

4. The coding method of claim 1, wherein step (b) comprises dividing the current block into an upper region, a middle region, and a lower region in a vertical direction, generating prediction values in the upper region using pixel values in the upper reference block, generating prediction values in the lower region using pixel values in the side reference block, and generating a prediction value of each pixel in the middle region using an average of pixel values in the respective upper and side reference blocks.

5. The coding method of claim 1, wherein step (b) comprises dividing the current block into a first region, a second region, and a third region in a horizontal direction, generating prediction values in the first region adjacent to the side reference block using pixel values in the side reference block, generating prediction values in the third region using pixel values in the upper reference block, and generating prediction values in the second region using pixel values in the upper and side reference blocks.

6. The coding method of claim 1, wherein step (b) comprises dividing the current block into two regions using a diagonal line crossing the current block starting from a top of an edge of the current block meeting the side reference block, generating prediction values of respective pixels in a region above the diagonal line using pixel values in the upper reference block, and generating prediction values of respective pixels in a region below the diagonal line using pixel values in the side reference block.

7. A non-transitory computer readable recording medium storing a program code for executing the coding method of claim 1 in a computer.

8. A coding apparatus comprising:

a hybrid predictor, which divides a current block to be predictively coded among blocks having a predetermined size, into which a chrominance component of an input image is divided, into a predetermined number of regions according to a predetermined number of prediction methods and generates prediction values of each pixel in the current block according to the respective prediction methods using a pixel value in an upper reference block adjacent to the current block and a pixel value in a side reference block adjacent to the current block;

a differential value generator, which generates differential values between the prediction values corresponding to the respective prediction methods and a corresponding real pixel value in the current block;

a selector, which selects a differential value requiring a least number of bits for coding among the differential values; and

a coder, which codes the selected differential value and information on a prediction method corresponding to the selected differential value using a predetermined coding method.

9. The coding apparatus of claim 8, wherein the hybrid predictor divides the current block into an upper region and a lower region in a vertical direction, generates prediction values in the upper region using pixel values in the upper reference block, and generates prediction values in the lower region using pixel values in the side reference block.

10. The coding apparatus of claim 8, wherein the hybrid predictor divides the current block into a first region and a second region in a horizontal direction, generates prediction values in the first region adjacent to the side reference block using pixel values in the side reference block, and generates prediction values in the second region using pixel values in the upper reference block.

11. The coding apparatus of claim 8, wherein the hybrid predictor divides the current block into an upper region, a middle region, and a lower region in a vertical direction, generates prediction values in the upper region using pixel values in the upper reference block, generates prediction values in the lower region using pixel values in the side reference block, and generates a prediction value of each pixel in the middle region using an average of pixel values in the respective upper and side reference blocks.

12. The coding apparatus of claim 8, wherein the hybrid predictor divides the current block into a first region, a second region, and a third region in a horizontal direction, generates prediction values in the first region adjacent to the side reference block using pixel values in the side reference block, generates prediction values in the third region using pixel values in the upper reference block, and generates prediction values in the second region using pixel values in the upper and side reference blocks.

13. The coding apparatus of claim 8, wherein the hybrid predictor divides the current block into two regions using a diagonal line crossing the current block starting from a top of an edge of the current block meeting the side reference block, generates prediction values of respective pixels in a region above the diagonal line using pixel values in the upper reference block, and generates prediction values of respective pixels in a region below the diagonal line using pixel values in the side reference block.