Real-time recursive filter to identify weather events using traffic CCTV video

• US 8,983,224 B1
• Filed: 08/27/2012
• Issued: 03/17/2015
• Est. Priority Date: 08/27/2012
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Exelis Incorporated (L3Harris Technologies, Inc.)
• Inventors: Matthews, Grant
• Primary Examiner(s): Wu, Jingge
• Application Number:
  US13/595,313
• Time in Patent Office: 932 Days
• Field of Search: 382/103, 382/107, 382264-265, 382/100, 340/963, 340968-969
• US Class Current: 382/265
• CPC Class Codes: G06T 2207/20024 Filtering details
• CPC Class Codes: G06T 2207/30192 Weather; Meteorology
• CPC Class Codes: G06T 7/215 Motion-based segmentation

Abstract

A program is implemented on a processor for executing the following steps: receiving images of a scene comprising successive frames from a camera, each frame including an array of pixels; filtering intensities of the array of pixels in a respective frame by using a Bessel Filter to compute a constant value for the respective frame; and summing a predetermined number of respective frames from the camera to determine rapid motion in the scene. The filter includes a Bessel filter, which is an n-pole recursive digital filter, where n is a positive integer.

Claims

1. A processor for executing the following steps:

receiving images of a scene comprising successive frames from a camera, each frame including an array of pixels;

filtering intensities of the array of pixels in a respective frame by using a Bessel Filter to compute a constant value for the respective frame, and

summing a predetermined number of respective frames from the camera to determine rapid motion in the scene,

wherein the rapid motion in the scene is a weather-related event, including motion of a rain fall, a hail storm, a snow storm, or a tornado, which is provided as notification to a remote station, and

the filtering is implemented using the following recursive relationship;

2. The processor of claim 1 wherein

filtering includes using a Bessel filter, which is an n-pole recursive digital filter, where n is a positive integer.

3. The processor of claim 2 wherein

the Bessel filter is an 8-pole recursive digital filter.

4. The processor of claim 1 wherein

each frame is defined by a 2-dimensional tensor of I_i,j(t), where i and j are a row and column, respectively, in the array of pixels, and

I are the intensities in the array of pixels at time t.

5. The processor of claim 1 wherein

the scene is captured by a closed circuit television (CCTV) camera, and

the rapid motion is a weather-related occurrence.

6. The processor of claim 5 wherein

the weather-related occurrence includes motion of a rain fall, a hail storm, a snow storm, or a tornado.

7. The processor of claim 2 wherein

the Bessel filter is defined by a ratio between (a) an (n−

1) order polynomial of a complex number and (b) an n order polynomial of a complex number,

where n is a positive number.

8. The program processor of claim 1 including the following step:

masking a first portion of the scene; and

wherein the step of filtering includes filtering intensities of the array of pixels in a second portion of the scene.

9. The processor of claim 8 wherein

the masking of the first portion of the scene is effective in removing motion of a non-weather-related occurrence in the scene.

10. The processor of claim 1 wherein

summing the predetermined number of respective frames includes summing eight successive frames from the camera.

11. A system for extracting weather-related events from a camera comprising:

a closed circuit television (CCTV) camera for monitoring a scene,

a filter for low pass filtering successive frames of the scene captured by the CCTV camera,

the filter including a Bessel function for computing constant values for the successive frames of the scene, and assigning a computed constant value to each of the successive frames, wherein a respective computed constant value multiplied by the intensities of a respective frame is defined as a filtered frame of the scene, and

a summer for summing a predetermined number of filtered frames of the scene,

wherein the summer is effective in determining rapid motion in the scene.

12. The system of claim 11 wherein

the filter includes a Bessel filter, which is an n-pole recursive digital filter, where n is a positive integer.

13. The system of claim 11 wherein

the rapid motion in the scene is a weather-related event, including motion of a rain fall, a hail storm, a snow storm, or a tornado.

14. The system of claim 12 wherein

the Bessel filter is defined by a ratio between (a) an (n−

1) order polynomial of a complex number and (b) an n order polynomial of a complex number,

where n is a positive number.

15. The system of claim 11 including:

a mask for masking a first portion of the scene captured by the CCTV camera, and

wherein the filter is configured to filter intensities of a second portion of the scene, in which the second portion is unmasked.

16. A method of extracting weather-related events from a camera comprising:

receiving successive frames captured by a closed circuit television (CCTV) camera of a scene,

filtering the successive frames of the scene captured by the CCTV camera by using a Bessel function for computing constant values for the successive frames of the scene,

assigning a computed constant value to each of the successive frames,

multiplying a respective computed constant value by intensities of the respective frame, wherein a result of the multiplying is defined as a filtered frame,

summing a predetermined number of filtered frames of the scene, and

determining rapid motion from the filtered frames of the scene.

17. The method of claim 16 wherein

the rapid motion in the scene is a weather-related event, including motion of a rain fall, a hail storm, a snow storm, or a tornado.

18. The method of claim 16 wherein

filtering includes a Bessel filter, which is defined by a ratio between (a) an (n−

1) order polynomial of a complex number and (b) an n order polynomial of a complex number,

where n is a positive number.

19. The method of claim 16 including the steps of:

masking a first portion of the scene captured by the CCTV camera, and

wherein filtering the successive frames of the scene includes filtering intensities of a second portion of the scene, in which the second portion is unmasked.