Video compression apparatus and method

• US 6,061,475 A
• Filed: 03/20/1998
• Issued: 05/09/2000
• Est. Priority Date: 03/20/1998
• Status: Expired due to Term

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Axcess, Inc.
• Inventors: Blair, Bruce A.
• Primary Examiner(s): Couso, Jose L.
• Assistant Examiner(s): Do, Anh Hong
• Application Number:
  US09/045,286
• Time in Patent Office: 781 Days
• Field of Search: 382/239, 382/201, 382/193, 382/194, 382/221
• US Class Current: 382/239
• CPC Class Codes: G06T 9/004 Predictors, e.g. intraframe, interframe coding

Abstract

The invention provides a method, and related apparatus, for improved compression of video images by determining optimum compression points using pixel-to-pixel slope comparison techniques and relaxable length limits. The method converts a digitized analog video signal into its piecewise linear equivalent, and then reduces the data stream by preserving only the break points. The linear segments may be as short as one pixel. After a predetermined slope length has been reached, the improved pointing technique combines length-limited points if the slopes of the corresponding linear segments are identical.

Claims

1. A method for compressing pixel data from a digitized image represented by a series of scan lines, each line having a plurality of segments, each segment comprising a plurality of pixels having corresponding pixel amplitude values, comprising the steps of:

setting a scan line segment'"'"'s first pixel to be a first point and assigning to the first point an amplitude value equal to the first pixel'"'"'s amplitude value and assigning to the first point'"'"'s length value to a value associated only with the first point;

selecting a next pixel of the scan line segment;

calculating a slope between the amplitude value of the most recently set point for the selected pixel and the amplitude value of the selected pixel;

predicting the amplitude value of a next subsequent pixel using the calculated slope;

comparing an actual amplitude value of the next subsequent pixel with the predicted amplitude value;

setting the selected pixel to be a next point if the value of the next subsequent pixel is not within a predetermined threshold range, the next point'"'"'s amplitude value being assigned to be equal to the selected pixel'"'"'s amplitude value and the next point'"'"'s length value being assigned to be equal to the number of pixels from the most recently set point to the next point, and the minimum point length value being one; and

repeating the next pixel selecting, the slope calculating, and the amplitude value predicting steps if the value of the next subsequent pixel falls within the predetermined threshold range.

2. A method for compressing pixel data as defined in claim 1, wherein the length value associated only with the first point is zero.

3. A method for compressing pixel data as defined in claim 1, further comprising, prior to the repeating step, the steps of setting the selected pixel to be a point if the number of pixels from the most recently set point to the selected pixel exceeds a predetermined length value.

4. A method for compressing pixel data as defined in claim 3, further comprising transmitting across a data link amplitude values and length values for points thus eliminating the transmission of amplitude values of pixels not set as point to compress the pixel data.

5. A method for compressing pixel data as defined in claim 4, further comprising decompressing the image based in the transmitted point values by interpolating the pixels between the transmitted points.

6. A method for compressing pixel data as defined in claim 3, further comprising:

comparing the slope for a first line segment between the most recently set point to a currently set point with the slope for a second line segment between the most recently set point and a point set just previous to the most recently set point;

eliminating the most recently set point if the slope for the first line segment is substantially equal to the slope for the second line segment and adding the most recently set point'"'"'s length value to the currently set point'"'"'s length value.

7. A method for compressing pixel data as defined in claim 1, wherein the length value associated only with the first point is zero.

8. A method for compressing pixel data from a digitized image, comprising the steps of:

setting a scan line segment'"'"'s first pixel to be a first point and assigning the first point'"'"'s amplitude value to be equal to the first pixel'"'"'s amplitude value and assigning the first point'"'"'s length value to a value associated only with the first point;

selecting the scan line segment'"'"'s next pixel;

setting the selected pixel to be a point if the number of pixels from the most recently set point to the selected point exceeds a predetermined length value;

repeating the selecting and setting steps until a point is set;

comparing the slope for a first line segment between the most recently set point to the currently set point with the slope for a second line segment between the most recently set point and a point just previous to the most recently set point;

eliminating the most recently set point if the slope for the first line segment is substantially equal to the slope for the second line segment and adding the most recently set point'"'"'s length value to the currently set point'"'"'s length value; and

repeating the selecting, setting, comparing, and eliminating steps until the end of the scan line segment.

9. A method for compressing pixel data as defined in claim 8, further comprising transmitting across a data link the point'"'"'s amplitude values and length values thus eliminating the transmission of amplitude values of pixels not set as point to compress the pixel data.

10. A method for compressing pixel data as defined in claim 9, further comprising decompressing the image based on the transmitted point values by interpolating the pixels between the transmitted points.

11. Apparatus for compressing pixel data from a digitized image represented by a series of scan lines, each line having a plurality of segments, each segment comprising a plurality of pixels having corresponding pixel amplitude values, comprising the steps of:

means for setting a scan line segment'"'"'s first pixel to be a first point and assigning to the first point an amplitude value equal to the first pixel'"'"'s amplitude value and assigning to the first point'"'"'s length value to a value associated only with the first point;

means for selecting a next pixel of the scan line segment;

means for calculating a slope between the amplitude value of the most recently set point for the selected pixel and the amplitude value of the selected pixel;

means for predicting the amplitude value of a next subsequent pixel using the calculated slope;

means for comparing an actual amplitude value of the next subsequent pixel with the predicted amplitude value;

means for setting the selected pixel to be a next point if the value of the next subsequent pixel is not within a predetermined threshold range, the next point'"'"'s amplitude value being assigned to be equal to the selected pixel'"'"'s amplitude value and the next point'"'"'s length value being assigned to be equal to the number of pixels from the most recently set point to the next point, and the minimum point length value being one; and

means for repeating the next pixel selecting, the slope calculating, and the amplitude value predicting if the value of the next subsequent pixel falls within the predetermined threshold range.

12. Apparatus for compressing pixel data as defined in claim 11, further comprising means for setting the selected pixel to be a point if the number of pixels from the most recently set point to the selected pixel exceeds a redetermined length value.

13. Apparatus for compressing pixel data as defined in claim 12, further comprising means for transmitting across a data link the point'"'"'s amplitude values and length values thus eliminating the transmission of amplitude values of pixels not set as point to compress the pixel data.

14. Apparatus for compressing pixel data as defined in claim 13, further comprising means for decompressing the image based in the transmitted point values by interpolating the pixels between the transmitted points.

15. Apparatus for compressing pixel data as defined in claim 12, further comprising:

means for comparing the slope for a first line segment between the most recently set point to a currently set point with the slope for a second line segment between the most recently set point and a point set just previous to the most recently set point;

means for eliminating the most recently set point if the slope for the first line segment is substantially equal to the slope for the second line segment and adding the most recently set point'"'"'s length value to the currently set point'"'"'s length value.