METHOD AND APPARATUS FOR COMPRESSING A REFERENCE FRAME IN ENCODING/DECODING MOVING IMAGES

• US 20100027617A1
• Filed: 07/29/2009
• Published: 02/04/2010
• Est. Priority Date: 07/29/2008
• Status: Abandoned Application

• Current Assignee: Kwangwoon University Industry, Samsung Electronics Co. Ltd.
• Original Assignee: Kwangwoon University Industry, Samsung Electronics Co. Ltd.
• Inventors: PARK, Sea-Nae, SIM, Dong-Gyu, LEE, Chang-Hyun, KIM, Yong-Serk, SONG, Kwan-Woong, JOO, Young-Hun
• Application Number:
  US12/511,497
• Publication Number:
  US 20100027617A1
• Time in Patent Office: Days
• US Class Current: 375/240.10
• CPC Class Codes: H04N 19/115 Selection of the code volume for a coding unit prior to coding
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock

Abstract

Provided is a method of compressing a reference frame in encoding or decoding moving images. A reference frame to be compressed is divided into basic processing blocks. The basic processing blocks are divided into sub-blocks. A maximum value and a minimum value of pixels within each sub-block are calculated. A necessary bit length needed for compression of each sub-block is obtained based on a difference between the maximum value and the minimum value. An average bit length of the sub-blocks within the basic processing block is calculated based on the calculated necessary bit lengths of the sub-blocks. Bits are variably allocated to each sub-block by adjusting the necessary bit length of each sub-block so that the average bit length of the sub-blocks within a corresponding basic processing block is less than or equal to a preset required bit length. Each sub-block is compressed to the allocated bits.

Claims

1. A method for compressing a reference frame in encoding or decoding moving images, the method comprising:

dividing a reference frame to be compressed into basic processing blocks;

dividing the basic processing blocks into sub-blocks;

calculating and storing a maximum value and a minimum value of pixels within each sub-block;

obtaining a necessary bit length needed for compression of each sub-block based on a difference between the maximum value and the minimum value;

calculating an average bit length of the sub-blocks within the basic processing block based on the calculated necessary bit lengths of the sub-blocks;

variably allocating bits to each sub-block by adjusting the necessary bit length of each sub-block so that the average bit length of the sub-blocks within a corresponding basic processing block is less than or equal to a preset required bit length to be allocated to a pixel within the corresponding basic processing block; and

compressing each sub-block to the allocated bits.

2. The method of claim 1, further comprising:

detecting the bits allocated to each sub-block within the corresponding basic processing block based on the stored maximum value and minimum value of the pixels within each sub-block; and

restoring the reference frame based on the bits detected for each sub-block.

3. The method of claim 1, wherein a size of the basic processing block is set to an 8×

8 pixel size.

4. The method of claim 1, wherein a size of the sub-block is set to a 4×

4 pixel size.

5. The method of claim 1, wherein the variably adjusting the necessary bit length of each sub-block comprises:

(a) reducing the necessary bit length of the sub-blocks by one bit in a pre-defined sub-block order;

(b) calculating the average bit length of the sub-blocks subsequent to the reducing the necessary bit length of a corresponding sub-block;

(c) determining whether the calculated average bit length exceeds the required bit length; and

(d) allocating the necessary bit lengths calculated in (a) to the sub-blocks, or repeating (a) through (c).

6. The method of claim 1, wherein the allocating the bits to each sub-block includes:

allocating the bits for the basic processing block to not exceed a size of the basic processing block multiplied by the preset required bit length.

7. An apparatus for compressing a reference frame in encoding or decoding moving images, the apparatus comprising:

a maximum/minimum value calculating unit which divides a reference frame to be compressed into basic processing blocks, divides the basic processing blocks into sub-blocks, and calculates a maximum value and a minimum value of pixels within each sub-block;

a maximum/minimum value storing unit which stores the calculated maximum and minimum values of each sub-block;

a sub-block bit calculating unit which determines a necessary bit length needed for compression of each sub-block based on a difference between the calculated maximum value and the minimum value, and calculates an average necessary bit length of the sub-blocks within a corresponding basic processing block, based on the calculated necessary bit lengths of the sub-blocks;

a bit allocating unit which variably allocates bits to each sub-block by adjusting the necessary bit length of the sub-blocks so that the average bit length of the sub-blocks within the corresponding basic processing block is less than or equal to a required bit length predefined for compression to be allocated to a pixel in the basic processing block, and compresses images to the allocated bits; and

a reference frame storing unit which stores the compressed reference frame.

8. The apparatus of claim 7, further comprising:

a bit allocation analyzing unit which detects the bits allocated to each sub-block based on the stored maximum value and the minimum value of the pixels within each sub-block to restore the reference frame stored in the reference frame storing unit; and

a reference frame restoring unit which restores the reference frame based on the bits detected by the bit allocation analyzing unit.

9. The apparatus of claim 7, wherein a size of the basic processing block is set to an 8×

8 pixel size.

10. The apparatus of claim 7, wherein a size of the sub-block is set to a 4×

4 pixel size.

11. The apparatus of claim 7, wherein the bit allocating unit variably adjusts the necessary bit length of each sub-block by decreasing the necessary bit lengths in steps, by one bit, from the sub-blocks in a pre-defined sub-block order.

12. The apparatus of claim 7, wherein the bit allocating unit variably allocates the bits to each sub-block by allocating the bits over the basic processing block to not exceed a size of the basic processing block multiplied by the required bit length.