FIELD-OF-VIEW CHANGE DETECTION

• US 20110043689A1
• Filed: 08/18/2009
• Published: 02/24/2011
• Est. Priority Date: 08/18/2009
• Status: Abandoned Application

• Current Assignee: Behavioral Recognition Systems Incorporated
• Original Assignee: Behavioral Recognition Systems Incorporated
• Inventors: Urech, Dennis Gene, Risinger, Lon William, Yang, Tao, Cobb, Wesley Kenneth, Saitwal, Kishor Adinath, Blythe, Bobby Ernest, Gottumukkal, Rajkiran Kumar
• Application Number:
  US12/543,281
• Publication Number:
  US 20110043689A1
• Time in Patent Office: Days
• US Class Current: 348/453
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 7/246 using feature-based methods, e.g. the tracking of corners or segments
• CPC Class Codes: G06V 20/49 Segmenting video sequences, i.e. computational techniques such as parsing or cutting the sequence, low-level clustering or determining units such as shots or scenes
• CPC Class Codes: H04N 5/147 Scene change detection
• CPC Class Codes: H04N 5/275 Generation of keying signals

Abstract

Techniques are disclosed for detecting a field-of-view change for a video feed. These techniques differentiate between a new or changed scene and a temporary variation in the scene to accurately detect field-of-view changes for the video feed. A field-of-view change is detected when the position of a camera providing the video feed changes, the video feed is switched to a different camera, the video feed is disconnected, or the camera providing the video feed is obscured. A false-positive field-of-view change is not detected when the scene changes due to a sudden variation in illumination, obstruction of a portion of the camera providing the video feed, blurred images due to an out-of-focus camera, or a transition between bright and dark light when the video feed transitions between color and near infrared capture modes.

Claims

1. A computer-implemented method for detecting a field-of-view change for a video feed, comprising:

receiving a stable background scene acquired from a plurality of images of the video feed;

receiving a new image from the video feed;

converting the stable background scene to a gray scale representation to produce a converted stable background scene;

extracting features representing image characteristics from the converted stable background scene to produce extracted features, wherein each extracted feature is associated with a position of a pixel; and

producing a field-of-view change signal that indicates if a field-of-view change has occurred in the video feed based on the extracted features, the converted stable background scene, and the new image.

2. The computer-implemented method of claim 1, further comprising converting the new image to a gray scale representation to produce a converted new image that is also used to produce the field-of-view change signal.

3. The computer-implemented method of claim 1, further comprising:

performing an optical flow analysis of the extracted features in the new image to produce tracking results; and

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the tracking results indicate that a feature movement threshold is not exceeded.

4. The computer-implemented method of claim 1, further comprising:

performing an optical flow analysis of the extracted features in the new image to produce tracking results; and

asserting the field-of-view change signal to indicate that a field-of-view change has occurred due to camera pan, tilt, or zoom when the tracking results indicate that a camera movement threshold is exceeded and the extracted features are moved in a systematic or orderly fashion based on locations of the extracted features in a polar coordinate system.

5. The computer-implemented method of claim 1, further comprising determining that the new image includes at least two colors and is not homogeneous.

6. The computer-implemented method of claim 1, further comprising:

determining that the new image includes single color and is homogeneous; and

indicating that the video feed is disconnected.

7. The computer-implemented method of claim 1, further comprising:

updating the stable background scene; and

repeating the extracting of the features to update the extracted features based on the updated stable background scene.

8. The computer-implemented method of claim 1, further comprising:

computing a phase spectrum of the converted stable background scene;

converting the new image to a gray scale representation to produce a converted new image;

computing a phase spectrum of the converted new image;

comparing the phase spectrum of the converted stable background scene to the phase spectrum of the new image to produce matching results; and

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the matching results indicate that a phase threshold is not exceeded.

9. The computer-implemented method of claim 1, further comprising:

extracting a first background area of the converted stable background scene that excludes foreground objects of the new image;

computing a phase spectrum of the first background area;

converting the new image to a gray scale representation to produce a converted new image;

extracting a second background area of the converted new image that excludes the foreground objects of the new image;

computing a phase spectrum of the second background area;

comparing the phase spectrum of the first background area to the phase spectrum of the second background area to produce background area matching results; and

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the background area matching results indicate that an area phase threshold is equaled or exceeded.

10. The computer-implemented method of claim 1, further comprising:

extracting a first background area of the converted stable background scene that excludes foreground objects of the new image;

computing a phase spectrum of the first background area;

converting the new image to a gray scale representation to produce a converted new image;

extracting a second background area of the converted new image that excludes the foreground objects of the new image;

computing a phase spectrum of the second background area;

comparing the phase spectrum of the first background area to the phase spectrum of the second background area to produce background area matching results; and

asserting the field-of-view change signal to indicate that a field-of-view change has occurred when the background area matching results indicate that an area phase threshold is not equaled or exceeded for a predetermined length of time.

11. A computer-readable storage medium containing a program which, when executed by a processor, performs an operation for detecting a field-of-view change for a video feed, the operation comprising:

receiving a stable background scene acquired from a plurality of images of the video feed;

receiving a new image from the video feed;

converting the stable background scene to a gray scale representation to produce a converted stable background scene;

extracting features representing image characteristics from the converted stable background scene to produce extracted features, wherein each extracted feature is associated with a position of a pixel; and

producing a field-of-view change signal that indicates if a field-of-view change has occurred in the video feed based on the extracted features, the converted stable background scene, and the new image.

12. The computer-readable storage medium of claim 11, further comprising converting the new image to a gray scale representation to produce a converted new image that is also used to produce the field-of-view change signal.

13. The computer-readable storage medium of claim 11, further comprising:

performing an optical flow analysis of the extracted features in the new image to produce tracking results;

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the tracking results indicate that a feature movement threshold is not exceeded; and

asserting the field-of-view change signal to indicate that a field-of-view change has occurred due to camera pan, tilt, or zoom when the tracking results indicate that a camera movement threshold is exceeded and the extracted features are moved in a systematic or orderly fashion based on locations of the extracted features in a polar coordinate system.

14. The computer-readable storage medium of claim 11, further comprising:

computing a phase spectrum of the converted stable background scene;

converting the new image to a gray scale representation to produce a converted new image;

computing a phase spectrum of the converted new image;

comparing the phase spectrum of the converted stable background scene to the phase spectrum of the new image to produce matching results; and

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the matching results indicate that a phase threshold is not exceeded.

15. The computer-readable storage medium of claim 11, further comprising:

extracting a first background area of the converted stable background scene that excludes foreground objects of the new image;

computing a phase spectrum of the first background area;

converting the new image to a gray scale representation to produce a converted new image;

extracting a second background area of the converted new image that excludes the foreground objects of the new image;

computing a phase spectrum of the second background area;

comparing the phase spectrum of the first background area to the phase spectrum of the second background area to produce background area matching results;

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the background area matching results indicate that an area phase threshold is equaled or exceeded; and

asserting the field-of-view change signal to indicate that a field-of-view change has occurred when the background area matching results indicate that an area phase threshold is not equaled or exceeded for a predetermined length of time.

16. A system, comprising:

a video input source configured to capture images included in the video feed;

a processor; and

a memory containing a program, which, when executed on the processor is configured to perform an operation for detecting a field-of-view change for the video feed, the operation comprising;

receiving a stable background scene acquired from a plurality of images of the video feed;

receiving a new image from the video feed;

converting the stable background scene to a gray scale representation to produce a converted stable background scene;

extracting features representing image characteristics from the converted stable background scene to produce extracted features, wherein each extracted feature is associated with a position of a pixel; and

producing a field-of-view change signal that indicates if a field-of-view change has occurred in the video feed based on the extracted features, the converted stable background scene, and the new image.

17. The system of claim 16, the operation further comprising converting the new image to a gray scale representation to produce a converted new image that is also used to produce the field-of-view change signal.

18. The system of claim 16, the operation further comprising:

performing an optical flow analysis of the extracted features in the new image to produce tracking results;

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the tracking results indicate that a feature movement threshold is not exceeded; and

asserting the field-of-view change signal to indicate that a field-of-view change has occurred due to camera pan, tilt, or zoom when the tracking results indicate that a camera movement threshold is exceeded and features are moved in a systematic or orderly fashion based on their locations in the polar coordinate system.

19. The system of claim 16, the operation further comprising:

computing a phase spectrum of the converted stable background scene;

converting the new image to a gray scale representation to produce a converted new image;

computing a phase spectrum of the converted new image;

comparing the phase spectrum of the converted stable background scene to the phase spectrum of the new image to produce matching results; and

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the matching results indicate that a phase threshold is not exceeded.

20. The system of claim 16, the operation further comprising:

extracting a first background area of the converted stable background scene that excludes foreground objects of the new image;

computing a phase spectrum of the first background area;

converting the new image to a gray scale representation to produce a converted new image;

extracting a second background area of the converted new image that excludes the foreground objects of the new image;

computing a phase spectrum of the second background area;

comparing the phase spectrum of the first background area to the phase spectrum of the second background area to produce background area matching results;

negating the field-of-view change signal to indicate that a field-of-view change has not occurred when the background area matching results indicate that an area phase threshold is equaled or exceeded; and

asserting the field-of-view change signal to indicate that a field-of-view change has occurred when the background area matching results indicate that an area phase threshold is not equaled or exceeded for a predetermined length of time.