Video coding system

• US 20030202596A1
• Filed: 05/19/2003
• Published: 10/30/2003
• Est. Priority Date: 01/21/2000
• Status: Active Grant

• Current Assignee: Meta Platforms, Inc. (f/k/a Facebook, Inc.)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Karczewicz, Marta, Lainema, Jani
• Granted Patent: US 7,200,174 B2
• Time in Patent Office: Days
• US Class Current: 375/240.16
• CPC Class Codes: G06T 7/223 using block-matching
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/513 Processing of motion vectors
• CPC Class Codes: H04N 19/52 by predictive encoding
• CPC Class Codes: H04N 19/521 for estimating the reliability of the determined motion vectors or motion vector field, e.g. for smoothing the motion vector field or for correcting motion vectors
• CPC Class Codes: H04N 19/53 Multi-resolution motion estimation; Hierarchical motion estimation
• CPC Class Codes: H04N 19/543 using regions
• CPC Class Codes: H04N 19/557 Motion estimation characterised by stopping computation or iteration based on certain criteria, e.g. error magnitude being too large or early exit
• CPC Class Codes: H04N 19/56 Motion estimation with initialisation of the vector search, e.g. estimating a good candidate to initiate a search

Abstract

A motion estimation method and system for a video coder are disclosed. The system comprises an input for a video image to be coded. It also comprises a hierarchical series of motion estimators of varying complexity, for estimating a motion vector field between the received image and a reference image. The subsequent motion estimator in the series is selected by a control means if a prediction error associated with the motion vector field estimated by the currently selected motion estimator exceeds a predetermined threshold. When available, inherited and predicted motion information is used to improve prediction quality.

Claims

1. An encoder for performing motion compensated encoding of a sequence of video frames comprising:

memory means for storing a reference frame; and

motion field estimation means for estimating the motion of picture elements in a current frame using at least the reference frame,

wherein the motion field estimation means uses prediction motion coefficients previously estimated for a least one picture element of the current frame in the estimation of motion coefficients for at least one other picture element of the current frame.

2. An encoder according to claim 1 in which the motion field estimation means calculates motion coefficients for a picture element by using a set of prediction motion coefficients previously estimated for at least one neighbouring picture element.

3. An encoder according to claim 2 in which the motion field estimation means calculates motion coefficients for a picture element by using a set of prediction motion coefficients previously estimated for more than one neighbouring picture element.

4. An encoder according to claim 3 in which the the motion field estimation means uses an averaged set of prediction motion coefficients averaged from motion information previously estimated for more than one neighbouring picture element.

5. An encoder according to claim 1 in which segmentation means is provided for segmenting a received frame into a plurality of picture elements.

6. An encoder according to claim 5 in which the segmentation means derives initial motion coefficients for a master picture element.

7. An encoder according to claim 1 in which the motion field estimation means comprises two separate motion estimators, one motion estimator for estimating motion coefficients based upon the predicted motion coefficients and one motion estimator for estimating motion coefficients based on the initial motion coefficients.

8. An encoder according to claim 7 in which both of the motion estimators estimate motion coefficients if the prediction motion coefficients and the initial motion coefficients are available.

9. An encoder according to claim 8 in which the motion field estimation means comprises selection means for selecting motion coefficients from either motion estimator to be used to code the current frame.

10. An encoder according to claim 7 in which only one motion estimator estimates motion coefficients if its corresponding motion coefficients are available and those of the other motion estimator are not available.

11. An encoder according to claim 1 in which the motion estimation means comprises a series of motion models of varying complexity.

12. An encoder according to claim 11 in which the series of motion models comprises a hierarchy including a zero motion model, a translational motion model, and an affine motion model.

13. An encoder according to claim 1 in which the motion estimation means comprises a series of minimisers, including a segment matching minimiser and a Gauss-Newton minimiser and a Quasi-Newton minimiser.

14. An encoder according to claim 11 comprising control means for selecting and using a subsequent motion model in the series if a prediction error associated with the motion vector field estimated by a currently selected motion estimator unit exceeds a predetermined threshold.

15. An encoder according to claim 11 comprising means for sub-sampling the current frame to produce a sub-sampled frame and for forwarding the sub-sampled frame to the series of motion models.

16. An encoder according to claim 13 comprising control means for selecting the amount of sub-sampling during minimisation depending on the change in prediction error.

17. An encoder according to claim 13 in which the means for sub-sampling comprises a series of sub-samplers varying in sub-sampling factors.

18. A codec comprising an encoder according to claim 1 and a decoder.

19. A mobile terminal comprising an encoder according to claim 1.

20. A data communications network comprising an encoder according to claim 1.

21. A method for performing motion compensated encoding of a sequence of video frames comprising the step of:

storing a reference frame;

estimating the motion of picture elements in a current frame using at least the reference frame; and

using a set of prediction motion coefficients previously estimated for a least one picture element of the current frame in the estimation of a set of motion coefficients for at least one other picture element of the current frame