Block artifacts detection

• US 20060218619A1
• Filed: 07/29/2004
• Published: 09/28/2006
• Est. Priority Date: 08/06/2003
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Dommisse, Ardjan, Hofman, Paul Michiel
• Application Number:
  US10/567,218
• Publication Number:
  US 20060218619A1
• Time in Patent Office: Days
• US Class Current: 725/148
• CPC Class Codes: G06T 7/00 Image analysis
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/85 using pre-processing or post-processing specially adapted for video compression
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

A block artifacts detection device (100) for detecting block artifacts in a video signal is disclosed. The block artifacts detection device (100) comprises: computing means (102) for computing a gradient signal on basis of the video signal; establishing means (104) for establishing a list of samples corresponding to respective local maximum values of the gradient signal; a histogram determining means (106) for determining a histogram of inter-sample distances, a first one of the inter-sample distances corresponding to a first distance between a first one of the samples and a second one of the samples succeeding the first one of the samples, and a second one of the inter-sample distances corresponding to a second distance between the first one of the samples and a third one of the samples succeeding the second one of the samples; and analyzing means (108) for analyzing the histogram of inter-sample distances and for producing a block artifact indicator on basis of the histogram.

Claims

1. A block artifacts detection device (100) for detecting block artifacts in a video signal, the block artifacts detection device (100) comprising:

computing means (102) for computing a gradient signal on basis of the video signal;

establishing means (104) for establishing a list of samples corresponding to respective local maximum values of the gradient signal;

histogram determining means (106) for determining a histogram of inter-sample distances, a first one of the inter-sample distances corresponding to a first distance between a first one of the samples and a second one of the samples succeeding the first one of the samples, and a second one of the inter-sample distances corresponding to a second distance between the first one of the samples and a third one of the samples succeeding the second one of the samples; and

analyzing means (108) for analyzing the histogram of inter-sample distances and for producing a block artifact indicator on basis of the histogram.

2. A block artifacts detection device (100) as claimed in claim 1, whereby the block artifact indicator corresponds with a spatial size of the block artifacts, the block artifact indicator being related to a particular inter-sample distance.

3. A block artifacts detection device (100) as claimed in claim 1, whereby the block artifact indicator corresponds with a measure of visibility of the block artifacts, the block artifact indicator being related to a frequency of occurrence of a particular inter-sample distance.

4. A block artifacts detection device (100) as claimed in claim 1, whereby the histogram of inter-sample distances is a weighted histogram.

5. A block artifacts detection device (100) as claimed in claim 4, whereby a weighting of the first distance is based on the local maximum value of the first one of the samples.

6. A block artifacts detection device (100) as claimed in claim 5, whereby the weighting of the first distance is based on a portion of the gradient signal comprising a sub-portion corresponding to the first one of the samples.

7. A block artifacts detection device (100) as claimed in claim 1, whereby the gradient signal is computed on basis of a first intermediate signal being computed by summation of respective pixel values of a number of video lines of the video signal.

8. A block artifacts detection device (100) as claimed in claim 1, whereby the gradient signal is computed by high-pass filtering of a first intermediate signal which is based on computing absolute differences between subsequent pixel values of the video signal.

9. An image processing apparatus (800) comprising:

receiving means (802) for receiving a video signal corresponding to a sequence of input images;

a block artifacts detection device (100) for detecting block artifacts in the video signal, as claimed in claim 1;

and

an image processing unit (804) for calculating a sequence of output images on basis of the sequence of input images, the image processing unit being controlled by the block artifacts detection device (100).

10. An image processing apparatus (800) as claimed in claim 9, characterized in further comprising a display device (806) for displaying the output images.

11. A method of detecting block artifacts in a video signal, the method comprising:

computing a gradient signal on basis of the video signal;

establishing a list of samples corresponding to respective local maximum values of the gradient signal;

determining a histogram of inter-sample distances, a first one of the inter-sample distances corresponding to a first distance between a first one of the samples and a second one of the samples succeeding the first one of the samples, and a second one of the inter-sample distances corresponding to a second distance between the first one of the samples and a third one of the samples succeeding the second one of the samples; and

analyzing the histogram of inter-sample distances and producing a block artifact indicator on basis of the histogram.

12. A computer program product to be loaded by a computer arrangement, comprising instructions to detect block artifacts in a video signal, the computer arrangement comprising processing means and a memory, the computer program product, after being loaded, providing said processing means with the capability to carry out:

computing a gradient signal on basis of the video signal;

establishing a list of samples corresponding to respective local maximum values of the gradient signal;

determining a histogram of inter-sample distances, a first one of the inter-sample distances corresponding to a first distance between a first one of the samples and a second one of the samples succeeding the first one of the samples, and a second one of the inter-sample distances corresponding to a second distance between the first one of the samples and a third one of the samples succeeding the second one of the samples; and

analyzing the histogram of inter-sample distances and producing a block artifact indicator on basis of the histogram.