Method for conversion between YUV 4:4:4 and YUV 4:2:0

• US 8,139,081 B1
• Filed: 09/07/2007
• Issued: 03/20/2012
• Est. Priority Date: 09/07/2007
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Zenverge, Inc. (NXP Semiconductors NV)
• Inventors: Daniel, Andrew D.
• Primary Examiner(s): Wang, Andrew
• Assistant Examiner(s): Merouan, Abderrahim
• Application Number:
  US11/851,933
• Time in Patent Office: 1,656 Days
• Field of Search: 345418-618, 348 26- 34, 348/441, 348 70- 71, 382162-167, 382/232, 708/100, 708/200, 708/203, 375/240.2
• US Class Current: 345/600
• CPC Class Codes: G06F 3/14 Digital output to display device ; Cooperation and interconnection of the display device with other functional units
• CPC Class Codes: G06T 9/00 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 Class Codes: G09G 2340/02 Handling of images in compressed format, e.g. JPEG, MPEG
• CPC Class Codes: G09G 2340/0407 Resolution change, inclusive of the use of different resolutions for different screen areas
• CPC Class Codes: G09G 2340/10 Mixing of images, i.e. displayed pixel being the result of an operation, e.g. adding, on the corresponding input pixels
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: H04N 19/27 involving both synthetic and natural picture components, e.g. synthetic natural hybrid coding [SNHC]
• CPC Class Codes: H04N 19/40 using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85

Abstract

Systems and methods for converting between a first color space format and a second color space format are described herein. The system receives a video cell in a first color space format comprising a plurality of pixels. Each pixel in the cell has a luminance value and a chrominance value. The luminance values of each pixel are compared to determine the brightest pixel in the received cell. The cell is downsampled to generate a second cell in a second color space format. The second cell in the second color space format comprises a downsampled chrominance value that is computed based at least in part on the chrominance value of the brightest pixel. The method advantageously reduces tinting of a high intensity pixel by the chrominance component of a neighboring low-intensity pixel.

Claims

1. A method performed by at least one of a computer processor and a solid-state device for conversion between a first color space format and a second color space format, the method comprising:

receiving a first cell comprising a plurality of pixels, wherein the first cell is represented by the first color space format, and wherein each pixel in the first cell has a luminance value and a chrominance value;

comparing the luminance values of the plurality of pixels in the first cell to determine a brightest pixel in the first cell, wherein the brightest pixel in the first cell has a luminance value at least as great as each of the other pixels in the first cell;

setting a downsampled chrominance value for the first cell equal to the chrominance value of the brightest pixel in the first cell;

generating a downsampled first cell, the downsampled first cell represented by the second color space format and comprising the downsampled chrominance value for the first cell.

2. The method of claim 1, further comprising:

receiving a second cell;

setting a downsampled chrominance value for the second cell equal to a chrominance value of the brightest pixel in the second cell in response to the luminance value of the brightest pixel in the second cell being at least a threshold value greater than each of the other pixels in the second cell; and

setting the downsampled chrominance value for the second cell equal to an average value of all chrominance values of pixels in the second cell in response to the luminance value of the brightest pixel in the second cell being less than the threshold value greater than each of the other pixels in the second cell.

3. The method of claim 2, wherein the threshold value is based on an average luminance value of the pixels in the second cell.

4. The method of claim 1, further comprising:

receiving a third cell;

weighting the chrominance value of each of a plurality of pixels in the third cell by a corresponding luminance value of the pixel in the third cell; and

determining a downsampled chrominance value for the third cell by passing the weighted chrominance values of the third cell through a downsampling filter.

5. The method of claim 4, wherein the downsampling filter is an averaging filter.

6. The method of claim 1, wherein the first color space format is YUV 4:

4;

4 color space format and the second color space format is YUV 4;

2;

0 color space format.

7. The method of claim 1, wherein the second color space format comprises one downsampled chrominance value for every 2×

2 grid of chrominance values in the first color space format.

8. A system for conversion between a first color space format and a second color space format comprising:

an input device, configured to receive a first cell comprising a plurality of pixels, wherein the first cell is represented by the first color space format, and wherein each pixel in the first cell has a luminance value and a chrominance value; and

a processor coupled to the input device, the processor configured to compare the luminance values of the plurality of pixels in the first cell to determine a brightest pixel in the first cell having a luminance value at least as great as each other pixel in the first cell, setting a downsampled chrominance value for the first cell equal to the chrominance value of the brightest pixel in the first cell, and generating a downsampled first cell, the downsampled first cell represented by the second color space format and comprising the downsampled chrominance value for the first cell.

9. The system of claim 8, wherein the processor is further configured to:

receive a second cell;

set a downsampled chrominance value for the second cell equal to a chrominance value of the brightest pixel in the second cell in response to the luminance value of the brightest pixel in the second cell being at least a threshold value greater than each of the other pixels in the second cell; and

set the downsampled chrominance value for the second cell equal to an average value of all chrominance values of pixels in the second cell in response to the luminance value being less than the threshold value greater than each of the other pixels in the second cell.

10. The system of claim 9, wherein the threshold value is based on an average luminance value of the pixels in the second cell.

11. The system of claim 8, wherein the processor is further configured to:

receive a third cell;

weight the chrominance value of each of a plurality of pixels in the third cell by a corresponding luminance value of the pixel in the third cell; and

determine a downsampled chrominance value for the third cell by passing the weighted chrominance values for the third cell through a downsampling filter.

12. The system of claim 11, wherein the downsampling filter is an averaging filter.

13. The system of claim 8, wherein the first color space format is YUV 4:

4;

4 color space format and the second color space format is YUV 4;

2;

0 color space format.

14. The system of claim 8, wherein the second color space format comprises one downsampled chrominance value for every 2×

2 grid of chrominance values in the first color space format.

15. A non-transitory computer readable storage medium structured to store instructions executable by a processing system, the instructions when executed cause the processing system to:

receive a first cell comprising a plurality of pixels, wherein the first cell is represented by the first color space format, and wherein each pixel in the first cell has a luminance value and a chrominance value;

compare the luminance values of the plurality of pixels in the first cell to determine a brightest pixel in the first cell, wherein the brightest pixel in the first cell has a luminance value at least as great as each of the other pixels in the first cell;

setting a downsampled chrominance value for the first cell equal to the chrominance value of the brightest pixel in the first cell;

generate a downsampled first cell, the downsampled first cell represented by the second color space format and comprising the downsampled chrominance value for the first cell.

16. The non-transitory computer readable medium of claim 15, the instructions when executed further causing the processing system to:

receiving a second cell;

set a downsampled chrominance value for the second cell equal to a chrominance value of the brightest pixel in the second cell in response to the luminance value of the brightest pixel in the second cell being at least a threshold value greater than each of the other pixels in the second cell; and

set the downsampled chrominance value for the second cell equal to an average value of all chrominance values of pixels in the second cell in response to the luminance value of the brightest pixel in the second cell being less than the threshold value greater than each of the other pixels in the second cell.

17. The non-transitory computer readable medium of claim 16, wherein the threshold value is based on an average luminance value of the pixels in the second cell.

18. The non-transitory computer readable medium of claim 15, the instructions when executed further causing the processing system to:

receive a third cell;

weight the chrominance value of each of a plurality of pixels in the third cell by a corresponding luminance value of the pixel in the third cell; and

determine a downsampled chrominance value for the third cell by passing the weighted chrominance values of the third cell through a downsampling filter.

19. The non-transitory computer readable medium of claim 18, wherein the downsampling filter is an averaging filter.

20. The non-transitory computer readable medium of claim 15, wherein the first color space format is YUV 4:

4;

4 color space format and the second color space format is YUV 4;

2;

0 color space format.

21. The non-transitory computer-readable storage medium of claim 15, wherein the second color space format comprises one downsampled chrominance value for every 2×

2 grid of chrominance values in the first color space format.