Enhanced background model employing object classification for improved background-foreground segmentation

• US 20040001612A1
• Filed: 06/28/2002
• Published: 01/01/2004
• Est. Priority Date: 06/28/2002
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Trajkovic, Miroslav, Gutta, Srinivas, Colmenarez, Antonio J.
• Granted Patent: US 7,190,809 B2
• Time in Patent Office: Days
• US Class Current: 382/107
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 7/11 Region-based segmentation
• CPC Class Codes: G06T 7/143 involving probabilistic approaches, e.g. Markov random field [MRF] modelling
• CPC Class Codes: G06T 7/194 involving foreground-background segmentation
• CPC Class Codes: G06T 7/215 Motion-based segmentation
• CPC Class Codes: G06V 10/28 Quantising the image, e.g. histogram thresholding for discrimination between background and foreground patterns
• CPC Class Codes: G06V 20/52 Surveillance or monitoring of activities, e.g. for recognising suspicious objects recognising microscopic objects G06V20/69

Abstract

A method and apparatus are disclosed for generating and maintaining enhanced background models for use in background-foreground segmentation. Background models are modified to contain an indication of objects that are typically stationary. Thereafter, if an object moves and has been previously identified as an object that is typically stationary, the object will not unnecessarily be identified as part of the foreground during background-foreground segmentation. In an exemplary implementation, moving objects are classified into two sets. A first set includes objects that typically move independently and a second set includes objects that are typically stationary. Generally, once an object is assigned to the second (stationary object) set, the object will remain in the background, even if the object is moved (normally, movement of the object would cause the object to become part of the foreground).

Claims

1. A method, comprising:

retrieving an image of a scene comprising a plurality of pixels;

obtaining a background model of said scene; and

providing an indication in said background model that an object in said background model is typically stationary.

2. The method of claim 1, further comprising the step of transferring pixel information associated with a moved object to a new location of said object.

3. The method of claim 1, further comprising the step of maintaining said object in said background.

4. The method of claim 1, further comprising the step of maintaining said object in said background even if said object is moved.

5. The method of claim 4, wherein said motion of an object in said background model is detected using an optical flow method.

6. The method of claim 5, wherein said optical flow method indicates a new location in said image of said moved object.

7. The method of claim 1, wherein said indication that an object in said background model is typically stationary is provided when said object is moved by more than a specified threshold.

8. The method of claim 1, wherein said step of obtaining a background model of said scene further comprises the step of determining at least one probability distribution corresponding to the pixels of the image, the step of determining performed by using a model wherein at least some pixels in the image are modeled as being dependent on other pixels.

9. The method of claim 1, wherein said background model comprises a term representing a probability of a global state of a scene and a term representing a probability of pixel appearances conditioned to the global state of the scene.

10. The method of claim 1, wherein the method further comprises the steps of:

providing a training image to the model;

determining parameters of the model; and

performing the step of providing a training image and determining parameters for a predetermined number of training images.

11. A system comprising:

a memory that stores computer-readable code; and

a processor operatively coupled to said memory, said processor configured to implement said computer-readable code, said computer-readable code configured to;

retrieve an image of a scene comprising a plurality of pixels;

obtain a background model of said scene; and

provide an indication in said background model that an object in said background model is typically stationary.

12. The system of claim 11, wherein said processor is further configured to transfer pixel information associated with a moved object to a new location of said object.

13. The system of claim 11, wherein said processor is further configured to maintain said object in said background.

14. The system of claim 11, wherein said processor is further configured to maintain said object in said background even if said object is moved.

15. The system of claim 14, wherein said motion of an object in said background model is detected using an optical flow system.

16. The system of claim 15, wherein said optical flow system indicates a new location in said image of said moved object.

17. The system of claim 11, wherein said indication that an object in said background model is typically stationary is provided when said object is moved by more than a specified threshold.

18. An article of manufacture, comprising:

a computer-readable medium having computer-readable code means embodied thereon, said computer-readable program code means comprising;

a step to retrieve an image of a scene comprising a plurality of pixels;

a step to obtain a background model of said scene; and

a step to provide an indication in said background model that an object in said background model is typically stationary.

19. A method, comprising:

retrieving an image of a scene comprising a plurality of pixels;

obtaining a background model of said scene; and

providing an indication in said background model that an object in said background model is an inanimate object.

20. The method of claim 19, further comprising the step of maintaining said inanimate object in said background.

21. The method of claim 19, further comprising the step of maintaining said inanimate object in said background even if said inanimate object is moved.