Method and apparatus for coding motion pictures utilizing motion compensation

• US 5,272,530 A
• Filed: 11/01/1991
• Issued: 12/21/1993
• Est. Priority Date: 11/01/1991
• Status: Expired due to Term

• Current Assignee: Aware Incorporated (Crowley Holdings Preferred LLC)
• Original Assignee: Aware Incorporated (Crowley Holdings Preferred LLC)
• Inventors: Cassereau, Philippe M.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US07/786,722
• Time in Patent Office: 781 Days
• Field of Search: 358/133, 358/135, 358/136, 358/12, 358/13, 358/105
• US Class Current: 375/240.12
• CPC Class Codes: H04N 19/30 using hierarchical techniques, e.g. scalability H04N19/63 takes precedence
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets

Abstract

An improved motion picture coding scheme is described which provides the benefits of both sub-band coding and motion compensation thereby providing greater degrees of compression than would be obtained using either of these techniques separately. The system generates high and low frequency frames from each pair of frames in the original motion picture. The high frequency represents the difference between the first and second frames of the motion picture. The pixels of the low frequency frame are either the average of two corresponding pixels, one from each of the original frames, or a value derived from a single pixel in the first frame. In the later case, the derived value is chosen to minimize artifacts that could hamper further compression of the low-frequency frame based on sub-band coding.

Claims

1. An apparatus for generating high and low-frequency component images from first and second input frames of a motion picture, said apparatus comprising:

first and second buffer means for storing first and second input arrays of pixel values respectively, said first array representing the intensity values in said first input frame and said second input array representing the intensity values in said second frame, said second input array being divided into a plurality of regions, each region storing a contiguous block of pixel values;

means for matching each said region in said second input array with a region of the same size in said first input array thereby defining a pixel in said first input array corresponding to each said pixel in said second input array;

means for assigning one of two values to each pixel value in said first input array, said first value being assigned if said pixel was included in a region matched to one and only one of said regions in said second input array by said matching means, and otherwise to said second value;

low-frequency buffer means for storing an array of pixel values representing the intensity values of said low-frequency component image, said low-frequency buffer means including one location corresponding to each said pixel value in said first input array;

high-frequency buffer means for storing an array of pixel values representing the intensity values of said high-frequency component image, said high-frequency buffer means including one location corresponding to each said pixel value in said second input array;

frame initialization means for causing said low-frequency buffer means to initially store a value related to the pixel value stored in said first input array at each location corresponding to a pixel in said first input array that was assigned said second value; and

filter means for combining each pixel in said second input array with said corresponding pixel in said first input array to generate high and low-frequency pixels, said high-frequency pixel being stored in said high-frequency buffer means in said location corresponding to said pixel in said second input array and said low-frequency pixel being stored in said low-frequency buffer means in said location corresponding to said pixel in said first input array if said assigning means assigned said first value to said corresponding pixel in said first input array.

2. The apparatus of claim 1 wherein each said initially stored values is equal to the low-frequency pixel that would have been generated by said filter means if said pixel value in said second input array were the same as said pixel value in said first input array.

3. An apparatus for generating first and second frames of a motion picture from a high-frequency image and a low-frequency image, said apparatus comprising:

high-frequency buffer means for storing a two-dimensional array of pixel values representing said high-frequency image;

low-frequency buffer means for storing a two-dimensional array of pixel values representing said low-frequency image;

means for storing information specifying a correspondence between each pixel value stored in said high-frequency buffer means and a pixel value stored in said low-frequency buffer means;

means for assigning a state to each pixel value in said low-frequency buffer means, said state having one of two values, said state being set to said first value if said pixel value in said low-frequency buffer means is specified as corresponding to a pixel in said high-frequency buffer one and only one time, and otherwise to said second value;

first generating means for generating a pixel in said first frame from said pixel value stored in said low-frequency buffer at a location depending on said pixel if said assigning means assigned said second value to said pixel value stored in said low-frequency buffer means;

second generating means for generating a pixel value in said first frame from a pixel value in said high-frequency frame at a location depending on said pixel and said corresponding pixel in said low-frequency frame when said assigning means assigns said first value to said pixel in said low-frequency frame; and

third generating means for generating a pixel in said second frame from each pair of corresponding pixels in said low-frequency buffer means and said high-frequency buffer means.

4. A method for generating high and low-frequency component images from first and second frames of a motion picture, said method comprising:

storing first and second input arrays of pixel values respectively, said first array representing the intensity values in said first input frame and said second input array representing the intensity values in said second frame, said second input array being divided into a plurality of regions, each region storing a contiguous block of pixel values;

matching each said region in said second input array with a region of the same size in said first input array thereby defining a pixel in said first input array corresponding to each said pixel in said second input array;

assigning one of two values to each pixel value in said first input array, said first value being assigned if said pixel was included in a region matched to one and only one of said regions in said second input array by said matching means, and otherwise to said second value;

storing an array of pixel values representing the intensity values of said low-frequency component image in a low-frequency buffer, said low-frequency buffer including one location corresponding to each said pixel value in said first input array;

storing an array of pixel values representing the intensity values of said high-frequency component image in a high-frequency buffer, said high-frequency buffer including one location corresponding to each said pixel value in said second input array;

causing said low-frequency buffer to initially store a value related to the pixel value stored in said first input array at each location corresponding to a pixel in said first input array that was assigned said second value; and

combining each pixel in said second input array with said corresponding pixel in said first input array to generate high and low-frequency pixels, said high-frequency pixel being stored in said high-frequency buffer in said location corresponding to said pixel in said second input array and said low-frequency pixel being stored in said low-frequency buffer in said location corresponding to said pixel in said first input array if said assigning means assigned said first value to said corresponding pixel in said first input array.

5. The method of claim 4 wherein each said initially stored values is equal to the low-frequency pixel that would have been generated by said filter means if said pixel value in said second input array were the same as said pixel value in said first input array.

6. A method for generating first and second frames of a motion picture from a high-frequency image and a low-frequency image, said method comprising:

storing a two-dimensional array of pixel values representing said high-frequency image in a high-frequency buffer;

storing a two-dimensional array of pixel values representing said low-frequency image in a low-frequency buffer;

storing information specifying a correspondence between each pixel value stored in said high-frequency buffer and a pixel value stored in said low-frequency buffer;

assigning a state to each pixel value in said low-frequency buffer, said state having one of two values, said state being set to said first value if said pixel value in said low-frequency buffer is specified as corresponding to a pixel in said high-frequency buffer one and only one time, and otherwise to said second value;

generating a pixel in said first frame from said pixel value stored in said low-frequency buffer at a location depending on said pixel if said assigning means assigned said second value to said pixel value stored in said low-frequency buffer means;

generating a pixel value in said first frame from a pixel value in said high-frequency frame at a location depending on said pixel and said corresponding pixel in said low-frequency frame when said assigning means assigns said first value to said pixel in said low-frequency frame; and

generating a pixel in said second frame from each pair of corresponding pixels in said low-frequency buffer and said high-frequency buffer.