Method of and system for enhancing distorted graphical information

• US 5,473,384 A
• Filed: 12/16/1993
• Issued: 12/05/1995
• Est. Priority Date: 12/16/1993
• Status: Expired due to Fees

• Current Assignee: AT&T IPM Corp. (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Liu, Tsann-Shyong, Jayant, Nuggehally S.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Burgess, Glenton B.
• Application Number:
  US08/168,598
• Time in Patent Office: 719 Days
• Field of Search: 348/470, 348/390, 348/396, 348/416, 348/607, 348/470, 348/613
• US Class Current: 348/470
• CPC Class Codes: H04N 19/527 Global motion vector estimation
• 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
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 19/90 using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals

Abstract

A system for and method of enhancing image/video signals to be decoded is disclosed. The system for and method of post-filtering uses, preferably, a temporal filter and a spatial filter, both of which are adaptive but neither is required to be adaptive. However, the system for and method of post-filtering may also be used with only an adaptive spatial post-filter. In this case, the performance is upper-bounded by the performance of systems using both the adaptive temporal and adaptive spatial post-filter.

Claims

1. A method of enhancing a distorted video signal, the distorted video signal comprising a set of image matrices adapted to be transmitted over a transmission medium of a digital communications setup, the digital communications setup comprising a coder, a decoder, and the transmission medium, the method comprising the steps of:

(a) filtering the set of image matrices with a first post-filter to generate a set of image intensity matrices; and

(b) filtering the set of image intensity matrices with a second post-filter to generate a set of enhanced image signals, the filtering comprising;

(1) classifying an image intensity matrix in the set of image intensity matrices into a set of edge pixels and a set of non-edge pixels;

(2) filtering the set of edge pixels with a first sub-filter of the second filter to generate a first portion of an enhanced image matrix in the set of enhanced image signals;

(3) classifying the non-edge pixels into a set of smooth pixels and non-smooth pixels;

(4) filtering the smooth pixels with a second sub-filter of the second filter to generate a second portion of the enhanced image matrix;

(5) classifying the non-smooth pixels into a set of moving pixels and a set of non-moving pixels, the set of non-moving pixels comprising a third portion of the enhanced image matrix;

(6) filtering the set of moving pixels with a third sub-filter of the second filter to generate a fourth portion of the enhanced image matrix;

(7) combining the first portion, the second portion, the third portion, and the fourth portion to form the enhanced image matrix; and

(8) repeating steps (b)(1) through (b)(7) for other enhanced image matrices in the set of enhanced image signals.

2. The method of claim 1 wherein the step of classifying the matrix comprises determining if an input image sequence is static, (d_i (x,j)=0).

3. The method of claim 1 wherein the first sub-filter is a multi-level median filter, the second sub-filter is a double median filter and the third sub-filter is a median filter.

4. The method of claim 1 wherein the first post-filter is comprised of a temporal post-filter and the second post-filter is comprised of a spatial post-filter.

5. The method of claim 4 wherein both the temporal post-filter and the spatial post-filter are adaptive.

6. The method of claim 1 further comprising the step of visually displaying the set of enhanced image matrices.

7. The method of claim 1 wherein the step of filtering the set of image matrices with the first post-filter comprises:

(a) classifying an image matrix in the set of image matrices into a set of static pixels and a set of dynamic pixels, the set of static pixels comprising a first portion of an image intensity matrix in the set of image intensity matrices;

(b) filtering the set of dynamic pixels with a motion compensating temporal filter to generate a second portion of the image intensity matrix;

(c) combining the first portion with the second portion to form an image intensity matrix; and

(d) repeating steps (a) through (c) for other image matrices in the set of image matrices.