Pipeline for high dynamic range video coding based on luminance independent chromaticity preprocessing
The disclosure describes a high dynamic range video coding pipeline that may reduce color artifacts and improve compression efficiency. The disclosed pipeline separates the luminance component from the chrominance components of an input signal (e.g., an RGB source video) and applies a scaling of the chrominance components before encoding, thereby reducing perceivable color artifacts while maintaining luminance quality.
1. A method, comprising:
receiving an additive color space digital image;
converting the received additive color space digital image into a uniform color space digital image having chrominance components and a luminance component;
scaling the chrominance components of the uniform color space digital image, wherein scaling the chrominance components of the uniform color space digital image comprises scaling a rectangular bounding box of a visual color gamut in a parameter space of the chrominance components;
quantizing the scaled chrominance components and the luminance component;
encoding the quantized chrominance components and the luminance component to create an encoded image; and
outputting a bitstream carrying the encoded image.
2. The method of claim 1 , wherein the uniform color space digital image is a Yu′v′ color space digital image, wherein Y is the luminance component, and wherein u′ and v′ are the chrominance components.
3. The method of claim 2 , wherein the rectangular bounding box is scaled by a factor between about 0.4 and about 1.6.
4. The method of claim 3 , wherein the rectangular bounding box is scaled by a factor of greater than 1.
5. The method of claim 3 , wherein the rectangular bounding box is scaled by a factor of less than 1.
6. The method of claim 2 , wherein scaling the rectangular bounding box comprises:
scaling the bounding box to the unity square [0, 1] 2 ; and
downscaling the scaled bounding box by a factor of s −1 where s≥1.
7. The method of claim 2 , further comprising: applying an electro-optical transfer function to the luminance component before the quantizing the luminance component.
8. The method of claim 7 , further comprising: subsampling the quantized chrominance components before encoding the quantized chrominance components.
9. The method of claim 2 , wherein the received additive color space digital image is a video frame.
10. The method of claim 2 , wherein the received additive color space digital image comprises a red-green-blue (RGB) color space digital image.
11. A non-transitory computer readable medium having instructions stored thereon that, when executed by one or more processors, causes a system to:
receive an additive color space digital image;
convert the received additive color space digital image into a uniform color space digital image having chrominance components and a luminance component;
scale the chrominance components of the uniform color space digital image, wherein scaling the chrominance components of the uniform color space digital image comprises scaling a rectangular bounding box of a visual color gamut in a parameter space of the chrominance components;
quantize the scaled chrominance components and the luminance component to create an encoded image;
encode the quantized chrominance components and the luminance component; and
output a bitstream carrying the encoded image.
12. The non-transitory computer readable medium of claim 11 , wherein the uniform color space digital image is a Yu′v′ color space image, wherein Y is the luminance component, and wherein u′ and v′ are the chrominance components.
13. The non-transitory computer readable medium of claim 12 , wherein the rectangular bounding box is scaled by a factor between about 0.4 and about 1.6.
14. The non-transitory computer readable medium of claim 13 , wherein the rectangular bounding box is scaled by a factor of greater than 1.
15. The non-transitory computer readable medium of claim 12 , wherein scaling the rectangular bounding box comprises:
scaling the bounding box to the unity square [0, 1] 2 ; and
downscaling the scaled bounding box by a factor of s −1 where s≥1.
16. The non-transitory computer readable medium of claim 12 , further comprising:
applying an electro-optical transfer function to the luminance component before the quantizing the luminance component,
subsampling the quantized chrominance components before encoding the quantized chrominance components.
17. The non-transitory computer readable medium of claim 12 , wherein the received additive color space digital image is a video frame.
18. The non-transitory computer readable medium of claim 12 , wherein the received additive color space digital image comprises a red-green-blue (RGB) color space image.