Machine method for compensating for non-linear picture transformations, E.G. zoom and pan, in a video image motion compensation system

• US 5,953,079 A
• Filed: 11/08/1996
• Issued: 09/14/1999
• Est. Priority Date: 03/24/1992
• Status: Expired due to Term

• Current Assignee: British Broadcasting Corporation
• Original Assignee: British Broadcasting Corporation
• Inventors: Thomson, Roderick, Burl, Michael
• Primary Examiner(s): LEE, RICHARD J
• Application Number:
  US08/745,986
• Time in Patent Office: 1,040 Days
• Field of Search: 348/384, 348/390, 348/409, 348/413, 348/416, 348/699, 348/402, 348/407, 348/420, 352/129, 382/232, 382/236, 382/238
• US Class Current: 348/699
• CPC Class Codes: H04N 19/527 Global motion vector estimation
• CPC Class Codes: H04N 23/68 for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/6811 based on the image signal
• CPC Class Codes: H04N 23/6815 by distinguishing pan or tilt from motion
• CPC Class Codes: H04N 5/144 Movement detection for video coding H04N19/503; analysis of motion in general G06T7/20

Abstract

Non-linear picture transformations in a video image motion compensation system are caused by camera zooms or rotations. Sets of trial vectors are derived for each block of the image representing peak correlation values between adjacent images in the sequence. A constant representing the non-linear transformation is estimated using the sets of trial vectors and this enables a vector representing the non-linear transformation to be added to the trial vector list for each block.

Claims

1. A machine method for compensating for non-linear picture transformations in a video image motion compensating system, in which a set of trial vectors is derived for each of a plurality of blocks, and in which each block is a region of a video frame, the method including:

(a) mapping estimated values of zoom for all pairs of said trial vectors in said blocks;

determining the location of a maximum of the values on said mapping, which location represents an estimated value for a zoom constant;

subtracting, from each of said trial vectors in each of said blocks, a motion vector corresponding to a zoom component equal to said estimated value for the zoom constant multiplied by a block location of a trial vector, the results of the subtractions being vector values from which the zoom component has been removed; and

(b) mapping said vector values for pan;

determining the location of a maximum of the values on said mapping for pan, which location represents an estimated value for pan; and

calculating new vectors for each block using the estimated values for both zoom and pan.

2. A method according to claim 1, wherein the location of said maximum which represents an estimated value for zoom is a complex number including a real component due to zoom and an imaginary component due to rotation.

3. A method according to claim 2, wherein said zoom is estimated from values of trial vectors in pairs of blocks using the equation ##EQU2## wherein V1 and V2 are values of background vectors at points whose positions are P1 and P2 relative to the center of the picture, and zoom_-- constant is said complex number whose real part represents zoom and whose imaginary part represents rotation.

4. A video image motion compensating system for compensating for non-linear picture transformations in a video image motion compensating system, in which a set of trial vectors is derived for each of a plurality of blocks, and in which each block is a region of a video frame, the system including:

mapping means for mapping estimated values of zoom for all pairs of said trial vectors in said blocks;

determination means for determining a location of a maximum of the values on said mapping, which location represents an estimated value for a zoom constant;

subtracting means for subtracting, from each of said trial vectors in each of said blocks, a motion vector corresponding to a zoom component equal to said estimated value for the zoom constant multiplied by a block location of a trial vector, the results of the subtractions being vector values from which the zoom component has been removed;

said mapping means also being provided for mapping said estimated values and said determining means also being provided for determining the location of said maximum of said estimated values, which location represents an estimated value for pan; and

calculating means for calculating new vectors for each block using said estimated values for zoom and pan.

5. A video image motion compensating system according to claim 4, wherein the location of said maximum which represents an estimated value for zoom is a complex number including a real component due to zoom and an imaginary component due to rotation.

6. A video image motion compensating system according to claim 5, wherein said zoom and rotation are estimated from values of trial vectors in pairs of blocks using the equation ##EQU3## wherein V1 and V2 are values of background vectors at points whose positions are P1 and P2 relative to the center of the picture, and zoom_-- constant is said complex number whose real part represents zoom and whose imaginary part represents rotation.

7. A machine method for compensating for non-linear picture transformations in a video image motion compensating system, in which method a set of trial vectors is derived for each of a plurality of blocks, wherein each block is a region of a video frame, the method including:

making a one dimensional plot of estimated values of one of said non-linear picture transformations for all pairs of said trial vectors in said blocks;

determining the location of a maximum of the values on said plot, which location represents an estimated value for a component of said one of said non-linear picture transformations;

subtracting, from each of said trial vectors in each of said blocks, a motion vector corresponding to the component of said one of said non-linear picture transformations equal to said estimated value multiplied by a block location of a trial vector, the results of the subtractions being vector values from which the component of said one of said non-linear picture transformations has been removed; and

splitting said vector values into X and Y components, which are then analyzed separately to estimate the X and Y components for another one of said non-linear picture transformations; and

calculating new vectors for each block using the estimated values for both of said non-linear picture transformations.

8. A method according to claim 7, wherein said non-linear picture transformations are zoom and pan.

9. A method according to claim 8, wherein said zoom is estimated from values of trial vectors in pairs of blocks using the equation ##EQU4## wherein V1 and V2 are values of background vectors at points whose positions are P1 and P2 relative to the center of the picture, and zoom_-- constant is a complex number whose real part represents zoom and whose imaginary part is ignored.

10. A video image motion compensating system for compensating for non-linear picture transformations in a video image motion compensating system, in which a set of trial vectors is derived for each of a plurality of blocks, wherein each block is a region of a video frame, the system including:

plot making means for making a one dimensional plot of estimated values of one of said non-linear picture transformations for all pairs of said trial vectors in said blocks;

means for determining the location of a maximum of the values on said plot, said location representing an estimated value for a component of said one of said non-linear picture transformations;

subtracting means for subtracting, from each of said trial vectors in each of said blocks, a motion vector corresponding to the component of said one of said non-linear picture transformations equal to said estimated value multiplied by a block location of a trial vector, the results of the subtractions being vector values from which the component of said one of said non-linear picture transformations has been removed;

means for splitting said vector values into X and Y components, which are then analyzed separately to estimate the X and Y components for another one of said non-linear picture transformations; and

calculating means for calculating new vectors for each block using estimated values for both of said non-linear picture transformations.

11. A video image motion compensating system according to claim 10, wherein said non-linear picture transformations are zoom and pan.

12. A video image motion compensating system according to claim 11, wherein said zoom is estimated from values of trial vectors in pairs of blocks using the equation ##EQU5## wherein V1 and V2 are values of background vectors at points whose positions are P1 and P2 relative to the center of the picture, and zoom_-- constant is a complex number whose real part represents zoom and whose imaginary part is ignored.