Encoding device and a method for encoding an image frame including selective restriction of offset compression values

Patent metadata

Field	Value
Publication number	US-12400368-B2
Application number	US-202218073993-A
Country	US
Kind code	B2
Filing date	Dec 2, 2022
Priority date	Dec 8, 2021
Publication date	Aug 26, 2025
Grant date	Aug 26, 2025

Abstract

An encoding device and a method for encoding an image frame comprising a plurality of pixel blocks are provided. A respective offset compression value is set for each of the plurality of pixel blocks based on an interest level associated with the pixel block, wherein each offset compression value defines an offset in relation to a reference compression value set for the image frame. In the image frame, one or more low contrast regions having a contrast which is below a predefined contrast threshold are identified. For pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest levels higher than a predefined offset compression threshold, the set offset compression values are selectively restricted to be at most equal to the predefined offset compression threshold. The image frame is then encoded using the set offset compression values.

First claim

The invention claimed is:

1. A method for encoding an image frame comprising a plurality of pixel blocks, the method comprising:
setting a respective offset compression value for each of the plurality of pixel blocks based on an interest level associated with the pixel block, wherein each offset compression value defines an offset in relation to a reference compression value set for the image frame;
identifying, in the image frame, one or more low contrast regions having a contrast which is below a predefined contrast threshold;
for pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest levels higher than a predefined offset compression threshold, selectively restricting the set offset compression values to be at most equal to the predefined offset compression threshold; and
encoding the image frame using the set offset compression values.

2. The method according to claim 1 , wherein the act of restricting is performed together with the act of setting, such that the act of setting comprises:
setting the respective offset compression value for each of the plurality of pixel blocks based on an interest level associated with the pixel block, wherein, for pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest level higher than the predefined offset compression threshold, the set offset compression values are selectively restricted to be at most equal to the predefined offset compression threshold.

3. The method according to claim 1 , wherein the act of setting is performed before the act of restricting, wherein the act of restricting comprises:
for pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest level higher than the predefined offset compression threshold, reducing the set offset compression values to be at most equal to the predefined offset compression threshold.

4. The method according to claim 1 , wherein the image frame comprises a plurality of regions each having a respective interest level, wherein, for each of the plurality of pixel blocks, the interest level associated with the pixel block is an interest level of a region of the plurality of regions in which the pixel block is located.

5. The method according to claim 1 , wherein the set offset compression values decrease with increasing interest level.

6. The method according to claim 1 , wherein the contrast is a contrast for a region of the image frame comprising more than one pixel block or a contrast for one pixel block.

7. The method according to claim 1 , wherein the offset compression values are offset quantization values, the reference compression value is a reference quantization value, and the predefined offset compression threshold is a predefined offset quantization threshold.

8. An encoding device configured to encode an image frame comprising a plurality of pixel blocks, the encoding device comprising:
circuitry configured to execute:
a setting function configured to set a respective offset compression value for each of the plurality of pixel blocks based on an interest level associated with the pixel block, wherein each offset compression value defines an offset in relation to a reference compression value set for the image frame,
an identifying function configured to identify, in the image frame, one or more low contrast regions having a contrast which is below a predefined contrast threshold, and
a restricting function configured to, for pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest level higher than a predefined offset compression threshold, selectively restricting the set offset compression values to be at most equal to the predefined offset

compression threshold; and
an encoder configured to encode the image frame using the set offset compression values.

9. The encoding device according to claim 8 , wherein the setting function and the restricting function are a combined function configured to set the respective offset compression value for each of the plurality of pixel blocks based on an interest level associated with the pixel block, wherein, for pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest level higher than the predefined offset compression threshold, the set offset compression values are selectively restricted to be at most equal to the predefined offset compression threshold.

10. The encoding device according to claim 8 , wherein the setting function and the restricting function are separate functions, and wherein the restricting function is configured to, for pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest level higher than the predefined offset compression threshold, reduce the set offset compression values to be at most equal to the predefined offset compression threshold.

11. The encoding device according to claim 8 , wherein the image frame comprises a plurality of regions each having a respective interest level, wherein, for each of the plurality of pixel blocks, the interest level associated with the pixel block is an interest level of a region of the plurality of regions in which the pixel block is located.

12. The encoding device according to claim 8 , wherein the set offset compression values decrease with increasing interest level.

13. The encoding device according to claim 8 , wherein the contrast is a contrast in a region of the image frame comprising more than one pixel block or a local contrast for one pixel block.

14. The encoding device according to claim 8 , wherein the offset compression values are offset quantization values, the reference compression value is a reference quantization value, and the predefined offset compression threshold is a predefined offset quantization threshold.

15. A non-transitory computer-readable storage medium having stored thereon instructions for implementing a method for encoding an image frame comprising a plurality of pixel blocks, the method comprising:
setting a respective offset compression value for each of the plurality of pixel blocks based on an interest level associated with the pixel block, wherein each offset compression value defines an offset in relation to a reference compression value set for the image frame;
identifying, in the image frame, one or more low contrast regions having a contrast which is below a predefined contrast threshold;
for pixel blocks within the one or more low contrast regions having set offset compression values based on the associated interest levels higher than a predefined offset compression threshold, selectively restricting (S 230 ) the set offset compression values to be at most equal to the predefined offset compression threshold; and
encoding the image frame using the set offset compression values.

Assignees

• Axis Ab

Inventors

• Edpalm Viktor
• Toresson Alexander
• Palmaeus Johan

Classifications

• G06T3/40

  Scaling of whole images or parts thereof, e.g. expanding or contracting · CPC title

• H04N19/14

  Coding unit complexity, e.g. amount of activity or edge presence estimation (H04N19/146 takes precedence) · CPC title

• H04N19/176

  the region being a block, e.g. a macroblock · CPC title

• G06T9/00 Primary

  Image coding (bandwidth or redundancy reduction for static pictures H04N1/41; coding or decoding of static colour picture signals H04N1/64; methods or arrangements for coding, decoding, compressing or decompressing digital video signals H04N19/00) · CPC title

• G06V10/40

  Extraction of image or video features · CPC title