Method of generating a blockiness indicator for a video signal

• US 9,131,213 B2
• Filed: 09/03/2008
• Issued: 09/08/2015
• Est. Priority Date: 09/07/2007
• Status: Active Grant

• Current Assignee: Evertz Microsystems Ltd. (Evertz Technologies Limited)
• Original Assignee: Evertz Microsystems Ltd. (Evertz Technologies Limited)
• Inventors: Wei, Jeff, Patel, Rakesh
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US12/203,433
• Publication Number:
  US 20090067511A1
• Time in Patent Office: 2,561 Days
• Field of Search: 375/240.27, 375/240.29, 375/E7.176, 375/E7.178, 375/E7.2, 348/184, 348/252, 348/425.2, 348/625, 358/3.15, 358/3.27, 370/521, 382/194, 382/268
• US Class Current: 1/1
• CPC Class Codes: H04N 17/004 for digital television systems
• CPC Class Codes: H04N 19/167 Position within a video image, e.g. region of interest [ROI]
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/182 the unit being a pixel
• CPC Class Codes: H04N 19/66 involving data partitioning, i.e. separation of data into packets or partitions according to importance
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness
• CPC Class Codes: H04N 19/865 with detection of the former encoding block subdivision in decompressed video
• CPC Class Codes: H04N 19/88 involving rearrangement of data among different coding units, e.g. shuffling, interleaving, scrambling or permutation of pixel data or permutation of transform coefficient data among different blocks
• CPC Class Codes: H04N 7/0155 using pixel blocks

Abstract

The described embodiments relate to methods and systems for detecting the blockiness of a video signal comprised of a number of pixels. The method includes the steps of calculating a total number of pixels in the video signal in flat blocks and visible block edge transitions, and generating a blockiness indicator from the total number of pixels in flat blocks and visible block edge transitions. The step of calculating the total number of pixels in flat blocks and the total number of pixels in visible block edge transitions may include calculating differential values for each pixel in the video signal, analyzing the differential values to determine if the pixel is part of a transition and/or a flat area and then counting the number of pixels in flat blocks and visible block edge transitions to produce a total number of pixels in flat blocks and a total number of pixels in visible block edge transitions.

Claims

1. A method of detecting a blockiness of a video signal comprised of a plurality of pixels the method comprising the steps of:

selecting a region of interest from the video signal;

for each pixel in the region of interest,

determining whether the pixel lies on a horizontal edge in which a visible transition occurs, a vertical edge in which a visible transition occurs, or in a flat area;

if the pixel lies on the horizontal edge or the vertical edge in which the visible transitions occur or in the flat area, determining if the pixel is a part of a visible horizontal transition along a macroblock border, a visible vertical transition along a macroblock border, a flat area or a flat macroblock;

calculating a total number of pixels in the region of interest by calculating a horizontal border transitions count, a vertical border transitions count, a flat area count and a macroblock flat area count, wherein;

the horizontal border transitions count represents a total number of pixels of the region of interest that are a part of the visible horizontal transition along the macroblock border,

the vertical border transitions count represents a total number of pixels of the region of interest that are a part of the visible vertical transition along the macroblock border,

the flat area count represents a total number of pixels of the region of interest that are a part of the flat area, and

the macroblock flat area count represents a total number of pixels of the region of interest that are a part of the flat macroblock; and

generating at least one blockiness indicator for the region of interest selected from the group consisting of a block border indicator, a flat area indicator and a flat block indicator, wherein the at least one blockiness indicator is based on at least one of the horizontal border transitions count, the vertical border transitions count, the flat area count and the macroblock flat area count.

2. The method of claim 1, wherein determining whether the pixel lies on the horizontal edge in which a visible transition occurs, the vertical edge in which the visible transition occurs or in the flat area comprises:

for each pixel in the region of interest,

calculating differential values for the pixel; and

analyzing the differential values to determine if the pixel lies on the horizontal edge in which the visible transition occurs, the vertical edge in which the visible transition occurs or in the flat area.

3. The method of claim 2 wherein calculating differential values includes selecting n^2−

1 pixels surrounding the pixel in the region of interest wherein n is any odd integer greater than one.

4. The method of claim 3 wherein n is equal to three.

5. The method of claim 1 wherein the at least one blockiness indicator includes a block border indicator.

6. The method of claim 1 wherein the at least one blockiness indicator includes a flat area indicator.

7. The method of claim 1 wherein the at least one blockiness indicator includes a flat block indicator.

8. The method of claim 1 wherein three blockiness indicators are generated.

9. The method of claim 8 wherein the three blockiness indicators are a block border indicator, a flat area indicator and a flat block indicator.

10. The method of claim 1 wherein the calculation step is performed using luma values of the video signal.

11. The method of claim 1 further comprising:

recursive filtering on the at least one blockiness indicator.

12. The method of claim 1 further comprising generating a blockiness alarm if the at least one blockiness indicator surpasses a configurable threshold.

13. The method of claim 1, wherein the total number of pixels in the region of interest is calculated by counting the number of pixels in the region of interest that lie on the horizontal and vertical transition along the macroblock border and in the flat macroblock.

14. A video signal compression system comprising:

a video source for producing a video signal comprised of a plurality of pixels;

a compression module for compressing the video signal at a compression level into a compressed video signal;

a decompression module for decompressing the compressed video signal into a decompressed video signal; and

a blockiness detection module configured to;

select a region of interest from the decompressed video signal;

for each pixel in the region of interest,

determine whether the pixel lies on a horizontal edge in which a visible transition occurs, vertical edge in which a visible transition occurs or in a flat area; and

if the pixel lies on the horizontal edge or the vertical edge in which the visible transitions occur or in the flat area, determine if the pixel is a part of a visible horizontal transition along a macroblock border, visible vertical transition along a macroblock border, a flat area or a flat macroblock;

calculate a total number of pixels in the region of interest by calculating a horizontal border transitions count, a vertical border transitions count, a flat area count and a macroblock flat area count, wherein;

the horizontal border transitions count represents a total number of pixels of the region of interest that are a part of the visible horizontal transition along the macroblock border,

the vertical border transitions count represents a total number of pixels of the region of interest that are a part of the visible vertical transition along the macroblock border,

the flat area count represents a total number of pixels of the region of interest that are a part of the flat area, and

the macroblock flat area count represents a total number of pixels of the region of interest that are a part of the flat macroblock; and

generate at least one blockiness indicator for the region of interest selected from the group consisting of a block border indicator, a flat area indicator and a flat block indicator, wherein the at least one blockiness indicator is based on at least one of the horizontal border transitions count, the vertical border transitions count, the flat area count and the macroblock flat area count,

wherein the compression module adjusts the compression level based on the at least one blockiness indicator.

15. The system of claim 14 wherein the blockiness detection module is further configured to:

for each pixel in the region of interest

calculate differential values for the pixel; and

analyze the differential values to determine if the pixel lies on the horizontal or vertical edge in which the visible transition occurs or in the flat area.

16. The system of claim 15 wherein calculating differential values includes selecting n^2−

1 pixels surrounding the pixel in the region of interest wherein n is any odd integer greater than one.

17. The system of claim 16 wherein n is equal to three.

18. The system of claim 14 wherein the blockiness detection module is configured to calculate the total number of pixels using luma values of the decompressed video signal.

19. The system of claim 14 wherein the blockiness detection module is further configured to perform recursive filtering on the at least one blockiness indicator.

20. The system of claim 14 further comprising a display module for displaying the blockiness indicator.

21. The system of claim 14 wherein the blockiness detection module is configured to generate a blockiness alarm if the at least one blockiness indicator surpasses a configurable threshold.

23. The system of claim 14, wherein the blockiness detection module is configured to count the number of pixels in the region of interest that lie on the horizontal and vertical transition along the macroblock border and in the flat macroblock to calculate the total number of pixels in the region of interest.

22. A video signal compression system comprising:

a video source for producing a video signal comprised of a plurality of pixels;

a compression module for compressing the video signal at a compression level into a compressed video signal;

a decompression module for decompressing the compressed video signal into a decompressed video signal;

a first blockiness detection module configured to;

select a region of interest from the decompressed video signal;

for each pixel in the region of interest from the decompressed video signal,

determine whether the pixel lies on a horizontal edge in which a visible transition occurs, a vertical edge in which a visible transition occurs or in a flat area; and

if the pixel lies on the horizontal edge or the vertical edge in which the visible transitions occur or in the flat area, determine if the pixel is a part of a visible horizontal transition along a macroblock border, a visible vertical transition along a macroblock border, a flat area or a flat macroblock;

calculate a total number of pixels of the region of interest selected from the decompressed video signal by calculating a horizontal border transitions count, a vertical border transitions count, a flat area count and a macroblock flat area count, wherein;

the horizontal border transitions count represents a total number of pixels of the region of interest that are a part of the visible horizontal transition along the macroblock border,

the vertical border transitions count represents a total number of pixels of the region of interest that are a part of the visible vertical transition along the macroblock border,

the flat area count represents a total number of pixels of the region of interest that are a part of the flat area, and

the macroblock flat area count represents a total number of pixels of the region of interest that are a part of the flat macroblock; and

generate at least one blockiness indicator for the region of interest selected from the decompressed video signal selected from the group consisting of a block border indicator, a flat area indicator and a flat block indicator, wherein the at least one blockiness indicator is based on at least one of the horizontal border transitions count, the vertical border transitions count, the flat area count and the macroblock flat area count; and

a second blockiness detection module configured to;

select a region of interest from the video signal;

for each pixel in the region of interest selected from the video signal,

determine whether the pixel lies on a horizontal edge in which a visible transition occurs, a vertical edge in which a visible transition occurs or in a flat area; and

if the pixel lies on the horizontal edge or vertical edge in which the visible transitions occur or in the flat area, determine if the pixel is a part of a visible horizontal transition along a macroblock border, a visible vertical transition along a macroblock border, a flat area or a flat macroblock;

calculate a total number of pixels of the region of interest selected from the video signal by calculating a horizontal border transitions count, a vertical border transitions count, a flat area count and a macroblock flat area count, wherein;

the horizontal border transitions count represents a total number of pixels of the region of interest that are a part of the visible horizontal transition along the macroblock border,

the vertical border transitions count represents a total number of pixels of the region of interest that are a part of the visible vertical transition along the macroblock border,

the flat area count represents a total number of pixels of the region of interest that are a part of the flat area, and

the macroblock flat area count represents a total number of pixels of the region of interest that are a part of the flat macroblock; and

generate at least one blockiness indicator for the region of interest selected from the video signal selected from the group consisting of a block border indicator, a flat area indicator and a flat block indicator, wherein the at least one blockiness indicator is based on at least one of the horizontal border transitions count, the vertical border transitions count, the flat area count and the macroblock flat area count,

wherein the compression module adjusts the compression level based on the at least one blockiness indicator for the region of interest selected from the decompressed video signal and the at least one blockiness indicator for the region of interest selected from the video signal.