Method and apparatus for the detection of motion in video

• US 6,493,041 B1
• Filed: 06/30/1998
• Issued: 12/10/2002
• Est. Priority Date: 06/30/1998
• Status: Expired due to Term

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Hanko, James G., Northcutt, J. Duane, Butcher, Lawrence L., Wall, Gerard A.
• Primary Examiner(s): RAO, ANAND SHASHIKANT
• Application Number:
  US09/108,066
• Time in Patent Office: 1,624 Days
• Field of Search: 348/169, 348/170, 348/143, 348/153, 348/154, 348/155, 375/240.06, 375/240.16, 375/240.17
• US Class Current: 348/699
• CPC Class Codes: H04N 5/144 Movement detection for video coding H04N19/503; analysis of motion in general G06T7/20

Abstract

The present invention comprises a method and apparatus for detection motion in video in which frames from an incoming video stream are digitized. The pixels of each incoming digitized frame are compared to the corresponding pixels of a reference frame, and differences between incoming pixels and reference pixels are determined. If the pixel difference for a pixel exceeds an applicable pixel difference threshold, the pixel is considered to be “different”. If the number of “different” pixels for a frame exceeds an applicable frame difference threshold, motion is considered to have occurred, and a motion detection signal is emitted. In one or more other embodiments, the applicable frame difference threshold is adjusted depending upon the current average motion being exhibited by the most recent frames, thereby taking into account “ambient” motion and minimizing the effects of phase lag. In one or more embodiments, different pixel difference thresholds may be assigned to different pixels or groups of pixels, thereby making certain regions of a camera'"'"'s field of view more or less sensitive to motion. In one or more embodiments of the invention, a new reference frame is selected when the first frame that exhibits no motion occurs after one or more frames that exhibit motion.

Claims

1. A method for detecting motion in video comprising the steps of:

digitizing an incoming video signal to produce digitized incoming video frames comprising image elements;

obtaining a difference value for each of said image elements of a first incoming video frame by comparing a value of said image element of said first incoming video frame to a value of a corresponding image element of a reference frame;

comparing said difference value to a difference value threshold for said image element;

maintaining a count of each image element whose difference value exceeds said difference value threshold for said image element; and

generating a motion detection indication when said count of image elements exceeds a first difference count threshold applicable to said first incoming video frame.

2. The method of claim 1 wherein said step of obtaining a difference value comprises obtaining a difference value that is a non-negative number.

3. The method of claim 1 further comprising:

repeating said obtaining, comparing, and maintaining step for a second incoming video frame; and

selecting said second incoming video frame as a reference frame when said count of image elements for said first incoming video frame exceeds said first difference count threshold and said count of image elements for said second incoming video frame is less than a second difference count threshold applicable to said second incoming video frame.

4. The method of claim 1 wherein said image elements comprise groups of pixels.

5. The method of claim 1 wherein the same difference value threshold is applicable to a plurality of adjacent image elements of said first incoming video frame.

6. The method of claim 3 further comprising the step of deriving said second difference count threshold from said first difference count threshold.

19. The method of claim 1 wherein said first difference count threshold is derived by trailing exponential averaging.

20. The method of claim 1 further comprising:

repeating said obtaining, comparing, and maintaining step for a second incoming video frame; and

selecting said second incoming video frame as a new reference frame only when a motion has been detected on said first incoming video frame and no motion has been detected on said second incoming video frame.

21. The method of claim 1 further comprising:

obtaining a second difference value for each of said image elements of a second incoming video frame by comparing a value of said image element of said second incoming video frame to a value of a corresponding image element of a reference frame;

comparing said second difference value to a difference value threshold for said image element of said second frame;

maintaining a second count of each image element of said second frame whose difference value exceeds said difference value threshold for said image element of said second frame; and

deriving a second difference count threshold applicable to said second frame, wherein said deriving step further comprises;

adding said maintained second count to said first difference count threshold; and

dividing a value resulting from said adding step by two.

22. The method of claim 1 further comprising:

selecting a new reference frame to replace said reference frame whenever a prior incoming video frame for which motion has been detected is followed by a subsequent incoming video frame for which no motion is detected.

23. The method of claim 22 wherein said selected reference frame is said subsequence incoming video frame.

7. A motion detection system comprising:

a video input device for obtaining a video input;

a digitizer for receiving said video input and for producing digitized video input frames comprising image elements;

a differencer for obtaining difference values between image elements of said input frames and corresponding image elements of corresponding reference frames;

a thresholder for determining for each of said difference values whether said difference value exceeds a corresponding difference threshold;

a difference counter for counting the number of said image elements for which said difference value exceeds said corresponding difference threshold; and

a motion detector for emitting a motion detection indicator when said number of said image elements exceeds a corresponding difference count threshold.

8. The motion detection system of claim 7 wherein said video input device comprises a video camera.

9. The motion detection system of claim 7 wherein said difference values comprise luminance different values.

10. The motion detection system of claim 7 further comprising a difference count threshold generator.

11. The motion detection system of claim 7 further comprising an adaptive difference count threshold generator.

12. The motion detection system of claim 7 further comprising an image element selector for selecting image elements and for assigning a difference threshold to said selected elements.

13. A computer program product comprising:

a computer processor usable medium having computer processor readable program code embodied therein for detecting motion in video, said computer processor readable program code comprising;

computer processor readable program code configured to cause a computer processor to digitize an incoming video signal to produce digitized incoming video frames comprising image elements;

computer processor readable program code configured to cause a computer processor to obtain a difference value for each of said image elements of a first incoming video frame by comparing a value of said image element of said first incoming video frame to a value of a corresponding image element of a reference frame;

computer processor readable program code configured to cause a computer processor to compare said difference value to a difference value threshold for said image element;

computer processor readable program code configured to cause a computer processor to maintain a count of each image element whose difference value exceeds said difference value threshold for said image element; and

computer processor readable program code configured to cause a computer processor to generate a motion detection indication when said count of image elements exceeds a first difference count threshold applicable to said first incoming video frame.

14. The computer program product of claim 13 wherein said computer processor readable program code configured to cause a computer processor to obtain a difference value comprises computer processor readable program code configured to cause a computer processor to obtain a difference value that is a non-negative number.

15. The computer program product of claim 13 further comprising:

computer processor readable program code configured to cause a computer processor to obtain a second difference value for each of said image elements of a second incoming video frame by comparing a value of said image element of said second incoming video frame to a value of a corresponding image element of a reference frame;

computer processor readable program code configured to cause a computer processor to compare said second difference value to a difference value threshold for said image element of said second frame;

computer processor readable program code configured to cause a computer processor to maintain a second count of each image element of said second frame whose difference value exceeds said difference value threshold for said image element of said second frame; and

computer processor readable program code configured to cause a computer processor to select said second incoming video frame as a reference frame when said count of image elements for said first incoming video frame exceeds said first difference count threshold and said second count of image elements for said second incoming video frame is less than a second difference count threshold applicable to said second incoming video frame.

16. The computer program product of claim 13 wherein said image elements comprise groups of pixels.

17. The computer program product of claim 13 wherein the same difference value threshold is applicable to a plurality of adjacent image elements of said first incoming video frame.

18. The computer program product of claim 15 further comprising computer processor readable program code configured to cause a computer processor to derive said second difference count threshold from said first. difference count threshold.