Techniques for motion estimation

• US 20110002387A1
• Filed: 01/14/2010
• Published: 01/06/2011
• Est. Priority Date: 07/03/2009
• Status: Abandoned Application

• Current Assignee: Tahoe Research Limited (f/k/a Learndale Limited) (Vector Capital Corporation)
• Original Assignee: Tahoe Research Limited (f/k/a Learndale Limited) (Vector Capital Corporation)
• Inventors: Zhang, Wenhao, Chiu, Yi-Jen, Xu, Lidong
• Application Number:
  US12/657,168
• Publication Number:
  US 20110002387A1
• Time in Patent Office: Days
• US Class Current: 375/240.15
• 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 19/57 Motion estimation characterised by a search window with variable size or shape
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

Techniques are described that can be used to apply motion estimation (ME) based on reconstructed reference pictures in a B frame or in a P frame at a video decoder. For a P frame, projective ME may be performed to obtain a motion vector (MV) for a current input block. In a B frame, both projective ME and mirror ME may be performed to obtain an MV for the current input block. A metric an be used determining a metric for each pair of MV0 and MV1 that is found in the search path, where the metric is based on a combination of a first, second, and third metrics. The first metric is based on temporal frame correlation, a second metric is based on spatial neighbors of the reference blocks, and a third metric is based on the spatial neighbors of the current block.

Claims

1. A computer-implemented method comprising:

specifying, at a video decoder, a search window in a first reference frame;

specifying a search path in the search window of the first reference frame;

for each motion vector MV0 in the search path, where each MV0 points from a current block to a reference block in the search window, determining a corresponding second motion vector MV1 that points to a reference block in a second reference frame, where the corresponding second motion vector MV1 is a function of MV0;

determining a metric for each pair of MV0 and MV1 that is found in the search path, wherein the metric comprises a combination of a first, second, and third metrics and wherein the first metric is based on temporal frame correlation, a second metric based on spatial neighbors of the reference blocks, and a third metric based on the spatial neighbors of the current block;

selecting the MV0 whose corresponding value for the metric is a desirable value, where the selected MV0 is used as a motion vector for the current block; and

providing a picture for display, wherein the picture for display is based in part on the selected MV0.

2. The method of claim 1, wherein the determining a metric comprises:

determining a weighted average of the first, second, and third metrics.

3. The method of claim 1, wherein the determining a metric comprises:

determining a first metric based on;

4. The method of claim 3, wherein the determining a metric comprises:

determining a second metric based on;

5. The method of claim 4, wherein the determining a metric comprises:

determining a third metric based on;

6. The method of claim 1, wherein:

the current block is in a bi-predictive picture,

the first forward reference frame comprises a forward reference frame, and

the second forward reference frame comprises a backward reference frame.

7. The method of claim 1, wherein:

the current block is in a predictive picture,

the first forward reference frame comprises a first forward reference frame, and

the second forward reference frame comprises a second forward reference frame.

8. The method of claim 1, wherein the metric comprises a sum of absolute differences value and the desirable value comprises a lowest sum of absolute differences value.

9. The method of claim 1, further comprising:

at an encoder, determining a motion vector for the current block by;

specifying a second search window in a third reference frame;

specifying a second search path in the second search window of the third reference frame;

for each motion vector MV2 in the second search path, where each MV2 points from the current block to a reference block in the second search window, determining a corresponding second motion vector MV3 that points to a reference block in a fourth reference frame;

determining a metric for each pair of MV2 and MV3 that is found in the second search path, wherein the metric comprises a combination of the first, second, and third metrics; and

selecting the MV2 whose corresponding value for the metric is a desirable value, where the selected MV2 is used as a motion vector for the current block.

10. A video decoder comprising:

logic to determine each motion vector MV0 in a search path, where each MV0 points from a current block to a reference block in a search window,

logic to determine a corresponding second motion vector MV1 that points to a reference block in a second reference frame, where the corresponding second motion vector MV1 is a function of MV0;

logic to determine a metric for each pair of MV0 and MV1 that is found in the search path, wherein the metric comprises a combination of a first, second, and third metrics and wherein the first metric is based on temporal frame correlation, a second metric based on spatial neighbors of the reference blocks, and a third metric based on the spatial neighbors of the current block; and

logic to select the MV0 whose corresponding value for the metric is a desirable value, where the selected MV0 is used as a motion vector for the current block.

11. The decoder of claim 10, further comprising:

logic to specify the search window in the first reference frame;

logic to specify the search path in the search window of the first reference frame; and

logic to specify a search window in the second reference frame.

12. The decoder of claim 10, wherein to determine a metric, the logic is to:

determine a first metric based on;

13. The decoder of claim 12, wherein to determine a metric, the logic is to:

determine a second metric based on;

14. The decoder of claim 13, wherein to determine a metric, the logic is to:

determine a third metric based on;

15. The decoder of claim 10, wherein:

the current block is in a bi-predictive picture,

the first forward reference frame comprises a forward reference frame, and

the second forward reference frame comprises a backward reference frame.

16. The decoder of claim 10, wherein:

the current block is in a predictive picture,

the first forward reference frame comprises a first forward reference frame, and

the second forward reference frame comprises a second forward reference frame.

17. A system comprising:

a display;

a memory; and

a processor communicatively coupled to the display, the processor configured to;

determine each motion vector MV0 in a search path, where each MV0 points from a current block to a reference block in a search window,

determine a corresponding second motion vector MV1 that points to a reference block in a second reference frame, where the corresponding second motion vector MV1 is a function of MV0,

determine a metric for each pair of MV0 and MV1 that is found in the search path, wherein the metric comprises a combination of a first, second, and third metrics and wherein the first metric is based on temporal frame correlation, a second metric based on spatial neighbors of the reference blocks, and a third metric based on the spatial neighbors of the current block, and

select the MV0 whose corresponding value for the metric is a desirable value, where the selected MV0 is used as a motion vector for the current block.

18. The system of claim 17, further comprising:

a wireless network interface communicatively coupled to the processor.

19. The system of claim 17, wherein to determine the metric, the processor is to:

determine a first metric based on;

20. The system of claim 17, wherein:

when the current block is in a bi-predictive picture, the first forward reference frame comprises a forward reference frame and the second forward reference frame comprises a backward reference frame and

when the current block is in a predictive picture, the first forward reference frame comprises a first forward reference frame and the second forward reference frame comprises a second forward reference frame.