Processing sequential video images to detect image motion among interlaced video fields or progressive video images

• US 6,532,264 B1
• Filed: 03/27/2000
• Issued: 03/11/2003
• Est. Priority Date: 03/27/2000
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Teranex, Inc. (Blackmagic Design Pty Limited)
• Inventors: Kahn, Barry
• Primary Examiner(s): Britton, Howard
• Assistant Examiner(s): Vo, Tung T.
• Application Number:
  US09/535,563
• Time in Patent Office: 1,079 Days
• Field of Search: H06/B.166, 375/240, 375/240.01, 375/240.02, 375/240.14, 375/240.15, 375/240.16, 348/452, 348/459, 348/699, 348/700
• US Class Current: 375/240.16
• CPC Class Codes: H04N 5/144 Movement detection for video coding H04N19/503; analysis of motion in general G06T7/20

Abstract

Video images are processed to detect image motion among sequential images (e.g., progressive non-interlaced images of a video signal and/or interlaced fields of a video signal), each image being represented using a plurality of pixels. Exemplary embodiments replace block-based motion estimation with pixel-based motion estimation. A correlation surface is generated for every pixel in a reference image, from which a motion vector and confidence metric (i.e., a measure of confidence in the accuracy of the motion vector) are extracted for each pixel.

Claims

1. Method for detecting image motion among at least two video images, each image being represented using a plurality of pixels, the method comprising the steps of:

comparing first information obtained from pixels used to represent a first image with second information obtained from pixels used to represent a second image, to produce a correlation surface representative of image motion;

extracting a motion vector from correlation data included in said correlation surface as a measure of image motion among the at least two images; and

producing a measure of confidence of accuracy with which said motion vector is generated, said measure being determined using a first point on said correlation surface and a second point on said correlation surface, said second point being spaced at least a predetermined distance from said first point on said correlation surface,

wherein the step of producing a measure of confidence includes a step of;

producing an average correlation value for each pixel, and

wherein the step of producing a measure of confidence includes steps of;

producing an absolute confidence metric as a ratio of a correlation value of the first point on the correlation surface to the average correlation value;

producing a relative confidence metric as a function of a difference between a correlation value of the second point and the correlation value of the first point; and

combining the absolute confidence metric and the relative confidence metric.

2. Method for detecting image motion among at least two video images, each image being represented using a plurality of pixels, the method comprising the steps of:

comparing first information obtained from pixels used to represent a first image with second information obtained from pixels used to represent a second image, to produce a correlation surface representative of image motion;

extracting a motion vector from correlation data included in said correlation surface as a measure of image motion among the at least two images;

producing a measure of confidence of accuracy with which said motion vector is generated, said measure being determined using a first point on said correlation surface and a second point on said correlation surface, said second point being spaced at least a predetermined distance from said first point on said correlation surface; and

identifying whether the motion vector requires filtering by comparing said motion vector to a motion vector of at least one adjacent pixel,

wherein the filtering includes steps of;

assigning weighted values to pixels in a neighborhood about a pixel of interest;

comparing a motion vector of one pixel in the neighborhood to motion vectors in remaining pixels of the neighborhood to calculate a weighted measure of the one pixel;

repeating the step of comparing for other predetermined pixels of the neighborhood to calculate plural weighted measures for the neighborhood;

comparing the plural weighted measures; and

selecting a motion vector from the pixel having a highest weighted measure as the motion vector for a pixel of interest in the neighborhood.

3. Method for processing at least two images to detect image motion among the at least two images, each image being represented using a plurality of pixels, the method comprising the steps of:

comparing first information obtained from pixels of a first field with second information obtained from pixels of a second field, the second field being temporally separated and spatially nonaligned with respect to the first field, to generate a first correlation surface;

comparing the first information with third information obtained from pixels of a third field, the third field being temporally separated and spatially aligned with the first field, to generate a second correlation surface;

combining said first and second correlation surfaces to produce a composite correlation surface;

extracting a motion vector from correlation data included in said composite correlation surface as a measure of image motion among the at least two video images; and

producing a measure of confidence of accuracy with which said motion vector is generated,

wherein the step of producing the measure of confidence includes a step of;

producing an average correlation value for each pixel, and

wherein the step of producing the measure of confidence includes steps of;

producing an absolute confidence metric as a ratio of a correlation value of the first point on the correlation surface to the average correlation value;

producing a relative confidence metric as a function of a difference between a correlation value of the second point and the correlation value of the first point; and

combining the absolute confidence metric and the relative confidence metric.

4. Method for processing at least two images to detect image motion among the at least two images, each image being represented using a plurality of pixels, the method comprising the steps of:

comparing first information obtained from pixels of a first field with second information obtained from pixels of a second field, the second field being temporally separated and spatially nonaligned with respect to the first field, to generate a first correlation surface;

comparing the first information with third information obtained from pixels of a third field, the third field being temporally separated and spatially aligned with the first field, to generate a second correlation surface;

combining said first and second correlation surfaces to produce a composite correlation surface;

extracting a motion vector from correlation data included in said composite correlation surface as a measure of image motion among the at least two video images; and

identifying whether the motion vector requires filtering by comparing said motion vector to a motion vector of at least one adjacent pixel,

wherein the filtering includes steps of;

assigning weighted values to pixels in a neighborhood about a pixel of interest;

comparing a motion vector of one pixel in the neighborhood to motion vectors in remaining pixels of the neighborhood to calculate a weighted measure for the one pixel;

repeating the step of comparing for other predetermined pixels of the neighborhood to calculate plural weighted measures for the neighborhood;

comparing the plural weighted measures; and

selecting a motion vector from the pixel having a highest weighted measure as the motion vector for pixel of interest.