Method and system for adaptive motion estimation

• US 20060188019A1
• Filed: 08/18/2005
• Published: 08/24/2006
• Est. Priority Date: 02/22/2005
• Status: Active Grant

• Current Assignee: Sunplus Technology Co., Ltd
• Original Assignee: Sunplus Technology Co., Ltd
• Inventors: Lin, Chun-Hung
• Granted Patent: US 7,809,063 B2
• Time in Patent Office: Days
• US Class Current: 375/240.160
• CPC Class Codes: H04N 19/139 Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
• CPC Class Codes: H04N 19/159 Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• 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 19/57 Motion estimation characterised by a search window with variable size or shape

Abstract

A method and system for adaptive motion estimation, which sets a search range in a previous frame in order to find a corresponding macroblock in the adaptive search range according to each macroblock of a current frame and to accordingly determine a corresponding motion vector. A motion vector is first determined by referring to a target macroblock of a current frame and reference macroblocks in a search range of a previous frame. Then, a compression mode is determined according to the target macroblock, the reference macroblocks and the motion vector, and a mode data is outputted corresponding to the compression mode. Finally, a search range is determined according to the mode data and the motion vector. Thus, the required computational amount and bandwidth can be saved and also the high-efficiency image compression is obtained.

Claims

1. A system for adaptive motion estimation, which sets a search range in a previous frame in order to find a corresponding block in the adaptive search range according to each block of a current frame and to accordingly determine a corresponding motion vector, the system comprising:

a motion estimation unit, which determines a motion vector by referring to a target block of a current frame and reference blocks in a search range of a previous frame;

a mode decision unit, which determines a compression mode according to the target block, the reference blocks and the motion vector and outputs a mode data corresponding to the compression mode;

a mode memory unit, which stores the mode data output by the mode decision unit;

a motion vector memory unit, which stores the motion vector determined by the motion estimation unit; and

a search range specifying unit, which determines a search range according to the mode data stored in the mode memory unit and the motion vector stored in the motion vector memory unit.

2. The system as claimed in claim 1, wherein the search range specifying unit computes an average of motion vectors of the previous frame according to the motion vector stored in the motion vector memory unit and a block number compressed by an intra mode corresponding to the mode data stored in the mode memory unit, and enlarges the search range when the average is greater than a predetermined search range threshold or the block number compressed by the intra mode is greater than predetermined a high motion vector threshold.

3. The system as claimed in claim 2, wherein the search range specifying unit reduces the search range when the average is not greater than the search range threshold and the block number compressed by the intra mode is smaller than a predetermined low motion vector threshold.

4. The system as claimed in claim 1, wherein the search range specifying unit computes an average of motion vectors of the previous frame according to the motion vector stored in the motion vector memory unit, and sets the search range as a predetermined first range when the average is greater than a predetermined first threshold.

5. The system as claimed in claim 4, wherein when the average is not greater than the predetermined first threshold, the search range specifying unit computes an averaged difference of the motion vectors of the previous frame according to the motion vector stored in the motion vector memory unit, and sets the search range as a predetermined second range when the averaged difference is greater than a predetermined second threshold, where the first range is greater than the second range.

6. The system as claimed in claim 5, wherein when the averaged difference is not greater than the predetermined second threshold, the search range specifying unit computes a block number compressed by an intra mode corresponding to the mode data stored in the mode memory unit, and sets the search range as a predetermined third range when the block number compressed by the intra mode is greater than a predetermined third threshold, where the second range is greater than the third range.

7. The system as claimed in claim 6, wherein when the block number compressed by the intra mode is not greater than the predetermined third threshold, the search range specifying unit computes a cbp average of blocks compressed by a zero cbp mode corresponding to the mode data stored in the mode memory unit, and sets the search range as a fourth range when the cbp average compressed by the zero cbp mode is greater than a predetermined fourth threshold, where the third range is greater than the fourth range.

8. The system as claimed in claim 6, wherein when the cbp average compressed by the zero cbp mode is not greater than the predetermined fourth threshold, the search range specifying unit computes a block number compressed by a skipped mode corresponding to the mode data stored in the mode memory unit, and sets the search range as a fifth range when the block number compressed by the skipped mode is greater than a predetermined sixth threshold, where the fifth range is greater than the sixth range.

9. The system as claimed in claim 1, wherein the blocks of current frame and previous frame are macroblocks.

10. The system as claimed in claim 1, wherein the blocks of current frame and previous frame are subblocks of macroblocks.

11. A method for adaptive motion estimation, which sets a search range in a previous frame in order to find a corresponding block in the search range according to each block of a current frame and to accordingly determine a corresponding motion vector, the method comprising the steps:

(A) determining a motion vector by referring to a target block of a current frame and reference blocks in a search range of a previous frame;

(B) determining a compression mode according to the target block, the reference blocks and the motion vector, and outputting a mode data corresponding to the compression mode;

(C) storing the mode data outputted by step (B);

(D) storing the motion vector determined by step (A); and

(E) determining a search range according to the mode data stored and the motion vector stored.

12. The method as claimed in claim 11, wherein step (E) computes an average of motion vectors of the previous frame according to the motion vector stored and a block number compressed by an intra mode corresponding to the mode data stored, and enlarges the search range when the average is greater than a predetermined search range threshold or the block number compressed by the intra mode is greater than a predetermined high motion vector threshold.

13. The method as claimed in claim 12, wherein step (E) reduces the search range when the average is not greater than the predetermined search range threshold and the block number compressed by the intra mode is smaller than a predetermined low motion vector threshold.

14. The method as claimed in claim 11, wherein step (E) computes an average of motion vectors of the previous frame according to the motion vector stored, and sets the search range as a predetermined first range when the average is greater than a predetermined first threshold.

15. The method as claimed in claim 14, wherein when the average is not greater than the predetermined first threshold, step (E) computes an averaged difference of the motion vectors of the previous frame according to the motion vector, and sets the search range as a predetermined second range when the averaged difference is greater than a predetermined second threshold, where the first range is greater than the second range.

16. The method as claimed in claim 15, wherein when the averaged difference is not greater than the predetermined second threshold, step (E) computes a block number compressed by an intra mode corresponding to the mode data, and sets the search range as a third range when the block number compressed by the intra mode is greater than a predetermined third threshold, where the second range is greater than the third range.

17. The method as claimed in claim 16, wherein when the block number compressed by the intra mode is not greater than the predetermined third threshold, step (E) computes a cbp average of blocks compressed by a zero cbp mode corresponding to the mode data, and sets the search range as a fourth range when the cbp average compressed by the zero cbp mode is greater than a predetermined fourth threshold, where the third range is greater than the fourth range.

18. The method as claimed in claim 17, wherein when the cbp average compressed by the zero cbp mode is not greater than the predetermined fourth threshold, step (E) computes a block number compressed by a skipped mode corresponding to the mode data, and sets the search range as a predetermined fifth range when the block number compressed by the skipped mode is greater than a predetermined fifth threshold, otherwise sets the search range as a predetermined sixth range, where the fourth range is greater than the fifth range and the fifth range is greater than the sixth range.

19. The system as claimed in claim 11, wherein the blocks of current frame and previous frame are macroblocks.

20. The system as claimed in claim 11, wherein the blocks of current frame and previous frame are subblocks of macroblocks.