Method of generating a blockiness indicator for a video signal

• US 10,244,243 B2
• Filed: 05/02/2017
• Issued: 03/26/2019
• 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:
  US15/584,694
• Publication Number:
  US 20170237994A1
• Time in Patent Office: 693 Days
• 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 determining if the pixel forms a part of at least one visible horizontal transition along a macroblock border, at least one visible vertical transition along a macroblock border, at least one flat area or at least one flat macroblock; calculating a horizontal border transitions count, a vertical border transitions count, a flat area count and a macroblock flat area count; 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.

Claims

1. A method of detecting blockiness in a video signal, the video signal comprising a plurality of successive video images, each video image comprising a plurality of pixels, the method comprising:

selecting a region of interest from the video signal, wherein the region of interest corresponds to an active viewing area, the active viewing area displaying a portion of a video image from the plurality of successive video images within a viewing area of a display screen, the region of interest including a plurality of macroblocks;

for each pixel in the region of interest, determining if the pixel forms a part of at least one visible horizontal transition along a macroblock border, at least one visible vertical transition along a macroblock border, at least one flat area or at least one flat macroblock;

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 form a part of a visible horizontal transition along a macroblock border,

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

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

the macroblock flat area count represents a total number of pixels of the region of interest that form a part of a 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, further comprising:

prior to determining if the pixel forms a part of the at least one visible horizontal transition along a macroblock border, the at least one visible vertical transition along a macroblock border, the at least one flat area or the at least one flat macroblock, determining for each pixel in the region of interest 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.

3. The method of claim 2, wherein determining whether 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 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 one horizontal edge in which the visible transition occurs, the vertical edge in which the visible transition occurs or in the flat area.

4. The method of claim 3 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.

5. The method of claim 3 wherein the calculation step is performed using luma values of each pixel in the region of interest.

6. The method of claim 3 wherein the calculation step is performed using chroma values of each pixel in the region of interest.

7. The method of claim 1 wherein the block border indicator is directly proportional to the blockiness of the region of interest of the video signal.

8. The method of claim 1 wherein the flat area indicator determines whether the region of interest contains static images.

9. The method of claim 1 wherein the flat block indicator is directly proportional to a degree of corruption of the video signal.

10. The method of claim 1, wherein:

the at least one blockiness indicator comprises a series of blockiness indicator values, wherein each blockiness indicator value corresponds to a video image in the plurality of successive video images, and

the method further comprises performing recursive filtering on the series of blockiness indicator values.

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

12. A method of adjusting a compression level applied to a video signal, the video signal comprising a plurality of successive video images, each video image comprising a plurality of pixels, the method comprising the steps of:

decompressing a compressed video signal into a decompressed video signal, the decompressed video signal comprising a decompressed plurality of successive video images, wherein the compressed video signal is a compressed version of the video signal at a first compression level;

selecting a region of interest from the decompressed video signal, wherein the region of interest corresponds to an active viewing area, the active viewing area displaying a portion of a video image from the decompressed plurality of successive video images within a viewing area of a display screen, wherein the region of interest including a plurality of macroblocks;

for each pixel in the region of interest, determining whether the pixel forms a part of at least one visible horizontal transition along a macroblock border, at least one visible vertical transition along a macroblock border, at least one flat area or at least one flat macroblock;

calculating a horizontal border transitions count, a vertical border transitions count, a flat area count or a macroblock flat area count, wherein;

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

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

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

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

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; and

adjusting the compression level based on the at least one blockiness indicator.

13. A video signal compression system comprising:

a video source for producing a video signal comprised of a plurality of successive video images, each video image comprising 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, wherein the region of interest corresponds to an active viewing area, the active viewing area displaying a portion of a video image from the plurality of successive video images within a viewing area of a display screen, the region of interest comprising a plurality of macroblocks;

for each pixel in the region of interest, determine whether the pixel forms a part of at least one visible horizontal transition along a macroblock border, at least one visible vertical transition along a macroblock border, at least one flat area or at least one flat macroblock;

calculate 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 form a part of a visible horizontal transition along a macroblock border,

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

the flat area count represents a total number of pixels of the region of interest that form a part of a flat area, and the macroblock flat area count represents a total number of pixels of the region of interest that form a part of a 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, and wherein the compression module adjusts the compression level based on the at least one blockiness indicator.

14. The system of claim 13, wherein the blockiness detection module is further configured to, prior to determining if the pixel forms a part of the at least one visible horizontal transition along a macroblock border, the at least one visible vertical transition along a macroblock border, the at least one flat area or the at least one flat macroblock, determine for each pixel in the region of interest 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.

15. The system of claim 13 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 edge in which the visible transition occurs, the 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 13 wherein the blockiness detection module is further configured to perform recursive filtering on the at least one blockiness indicator.

18. The system of claim 13 further comprising a display module for displaying the blockiness indicator.

19. The system of claim 13 wherein the blockiness detection module is configured to generate a blockiness alarm if the at least one blockiness indicator surpasses a configurable threshold.

20. A video signal compression system comprising:

a video source for producing a video signal, the video signal comprising a first plurality of successive video images, each video image comprising 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, the decompressed video signal comprising a second plurality of successive video images;

a first blockiness detection module configured to;

select a region of interest from the decompressed video signal, wherein the region of interest corresponds to a first active viewing area, the first active viewing area displaying a portion of a video image from the second plurality of successive video images within a viewing area of a display screen;

for each pixel in the region of interest from the decompressed video signal, determining if the pixel forms a part of at least one visible horizontal transition along a macroblock border, at least one visible vertical transition along a macroblock border, at least one flat area or at least one 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 or a macroblock flat area count, wherein;

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

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

the flat area count represents a total number of pixels that form a part of a flat area, and

the macroblock flat area count represents a total number of pixels that form a part of a flat macroblock; and

generate at least one blockiness indicator 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, wherein the region of interest corresponds to a second active viewing area, the second active viewing area displaying a portion of a video image from the first plurality of successive video images within the viewing area of the display screen;

for each pixel in the region of interest selected from the video signal, determine if the pixel forms a part of at least one visible horizontal transition along a macroblock border, at least one visible vertical transition along a macroblock border, at least one flat area or at least one 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 or 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 a 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 a macroblock border,

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

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