US 8,285,046 B2Granted

Adaptive update of background pixel thresholds using sudden illumination change detection

AssigneeBehavioral Recognition Systems, Inc.

InventorsWesley Kenneth Cobb, Kishor Adinath Saitwal, Bobby Ernest Blythe, Tao Yang

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Abstract

Techniques are disclosed for a computer vision engine to update both a background model and thresholds used to classify pixels as depicting scene foreground or background in response to detecting that a sudden illumination changes has occurred in a sequence of video frames. The threshold values may be used to specify how much pixel a given pixel may differ from corresponding values in the background model before being classified as depicting foreground. When a sudden illumination change is detected, the values for pixels affected by sudden illumination change may be used to update the value in the background image to reflect the value for that pixel following the sudden illumination change as well as update the threshold for classifying that pixel as depicting foreground/background in subsequent frames of video.

Claims24

Dependent claims

A computer-implemented method for analyzing a sequence of video frames depicting a scene captured by a video camera, the method comprising:

classifying each of a plurality of pixels in a first frame of the sequence of video frames as depicting one of scene background and scene foreground, wherein each pixel is classified based on a comparison of (i) a relative deviation determined using a pixel value from the first frame and a corresponding pixel value in a background image and (ii) a classification threshold assigned to each pixel in the background image;
and
upon determining that a group of pixels in the first frame were classified as depicting scene foreground as a result of a sudden illumination change (SIC):
for each pixel in the group of pixels:
re-classifying the pixel as depicting scene background, and
decreasing the classification threshold assigned to the pixel to a value below the relative deviation determined for the pixel;
and
for one or more successive frames of video following the first frame:
updating the pixel values in the background image corresponding to the group of pixels, based on pixel values obtained from video frames following the first frame, and
increasing the classification threshold assigned to pixels in the background image for pixels corresponding to the group of pixels.

7 more elements

A computer-readable storage medium containing a program which, when executed by a processor, performs an operation for analyzing a sequence of video frames depicting a scene captured by a video camera, the operation comprising:

classifying each of a plurality of pixels in a first frame of the sequence of video frames as depicting one of scene background and scene foreground, wherein each pixel is classified based on a comparison of (i) a relative deviation determined using a pixel value from the first frame and a corresponding pixel value in a background image and (ii) a classification threshold assigned to each pixel in the background image;
and
upon determining that a group of pixels in the first frame were classified as depicting scene foreground as a result of a sudden illumination change (SIC):
for each pixel in the group of pixels:
re-classifying the pixel as depicting scene background, and
decreasing the classification threshold assigned to a value below the relative deviation determined for the pixel using the pixel value from the first frame and the corresponding pixel value from the background image;
and
for one or more successive frames of video following the first frame:
updating the pixel values in the background image corresponding to the group of pixels, based on pixel values obtained from video frames following the first frame, and
increasing the classification threshold assigned to pixels in the background image for pixels corresponding to the group of pixels.

7 more elements

A system, comprising:

a video input source configured to provide a sequence of video frames, each depicting a scene;
a processor;
and
a memory containing a program, which, when executed on the processor is configured to perform an operation for analyzing the scene, as depicted by the sequence of video frames captured by the video input source, the operation comprising:
classifying each of a plurality of pixels in a first frame of the sequence of video frames as depicting one of scene background and scene foreground, wherein each pixel is classified based on a comparison of (i) a relative deviation determined using a pixel value from the first frame and a corresponding pixel value in a background image and (ii) a classification threshold assigned to each pixel in the background image,
upon determining that a group of pixels in the first frame were classified as depicting scene foreground as a result of a sudden illumination change (SIC):
for each pixel in the group of pixels:
re-classifying the pixel as depicting scene background;
and
decreasing the classification threshold assigned to a value below the relative deviation determined for the pixel using the pixel value from the first frame and the corresponding pixel value from the background image, and
for one or more successive frames of video following the first frame:
updating the pixel values in the background image corresponding to the group of pixels, based on pixel values obtained from video frames following the first frame;
and
increasing the classification threshold assigned to pixels in the background image for pixels corresponding to the group of pixels.

11 more elements

Dependencies are inferred from the claim text.