High Dynamic Range Non-Constant Luminance Video Encoding and Decoding Method and Apparatus
Compounding reproduction errors in the luminance of a pixel encoded by a non-constant luminance video encoder is High Dynamic Range (HDR) video content, which is starting to become more widely supported by commercially available display devices. HDR video content contains information that covers a wider luminance range than traditional, non-HDR video content known as Low Dynamic Range (LDR) video content. The present disclosure is directed to an apparatus and method for reducing errors in reproduced luminance of HDR video content (and other types of video content) at a video encoder and/or video decoder due to non-constant luminance video encoding.
1 . An encoder, comprising:
a spatial low-pass filter;
a filter controller configured to control the spatial low-pass filter to provide more spatial smoothing to a green component of a first pixel than to a green component of a second pixel based on a color of the first pixel being closer to a red or blue vertex of a color gamut than a color of the first pixel;
a perceptual transfer function configured to perceptually quantize the green component of the first pixel after the green component has been spatially low-pass filtered by the spatial low-pass filter to provide a perceptually quantized first color component;
a decomposition transformation matrix configured to transform the perceptually quantized green color component, a perceptually quantized red color component, and a perceptually quantized blue color component into a luma component and chroma components; and
a subsampling filter configured to subsample the chroma components.
2 . The encoder of claim 1 , wherein the filter controller is configured to control the spatial low-pass filter to provide no spatial smoothing to the green component of the second pixel based on the green component of the second pixel being above a first threshold or based on a red or blue component of the second pixel being below a second threshold.
3 . The encoder of claim 1 , wherein the filter controller is configured to control the spatial low-pass filter to provide at least some spatial smoothing to the green component of the second pixel based on the green component of the second pixel being below a first threshold and a red or blue component of the second pixel being above a second threshold.
4 . The encoder of claim 1 , wherein the filter controller is configured to control the spatial low-pass filter to provide at least some spatial smoothing to the green component of the first pixel based on the green component of first pixel being below a first threshold and a red or blue component of the first pixel being above a second threshold.
5 . The encoder of claim 1 , wherein the color of the first pixel is defined by the green component of the first pixel, a red component of the first pixel, and a blue component of the first pixel.
6 . The encoder of claim 1 , wherein the filter controller is configured to control an amount of spatial smoothing provided by the spatial low-pass filter to the green component of the first pixel by adjusting a distribution of weights used by the spatial low-pass filter to weight the green component of the first pixel and the green components of pixels in a surrounding neighborhood of the first pixel.
7 . An encoder, comprising:
a spatial low-pass filter configured to spatially smooth a first color component of a pixel to provide a filtered first color component;
a filter controller configured to control the spatial low-pass filter based on the first color component of the pixel and at least one of a second or third color component of the pixel;
a perceptual transfer function configured to perceptually quantize the filtered first color component to provide a perceptually quantized first color component;
a decomposition transformation matrix configured to transform the perceptually quantized first color component, a perceptually quantized second color component, and a perceptually quantized third color component into a luma component and chroma components; and
a subsampling filter configured to subsample the chroma components.
8 . The encoder of claim 7 , wherein the first color component of the pixel is green.
9 . The encoder of claim 7 , wherein the filter controller is configured to enable and disable the spatial low-pass filter based on a position, in a color gamut, of a point that corresponds to the first color component of the pixel, the second color component of the pixel, and the third color component of the pixel.
10 . The encoder of claim 7 , wherein the filter controller is configured to adjust an amount of smoothing provided by the spatial low-pass filter based on a position, in a color gamut, of a point that corresponds to the first color component of the pixel, the second color component of the pixel, and the third color component of the pixel.
11 . The encoder of claim 7 , wherein the filter controller is configured to enable the spatial low-pass filter based on the first color component of the pixel, the second color component of the pixel, and the third color component of the pixel corresponding to a point within a border region of a color gamut.
12 . The encoder of claim 7 , wherein the filter controller is configured to enable the spatial low-pass filter based on the first color component of the pixel being below a first threshold and the second color component of the pixel being above a second threshold.
13 . The encoder of claim 7 , further comprising:
an additional pair of spatial low-pass filters configured to spatially low-pass filter the second color component of the pixel before the second color component of the pixel is perceptually quantized and spatially low-pass filter the third color component of the pixel before the third color component of the pixel is perceptually quantized.
14 . The encoder of claim 12 , wherein the filter controller is further configured to control the additional pair of spatial low-pass filters.
15 . A method for encoding, comprising:
spatially low-pass filtering a first color component of a pixel, using a spatial low-pass filter, based on the first color component of the pixel and at least one of a second or third color component of the pixel to provide a filtered first color component;
perceptually quantizing the filtered first color component to provide a perceptually quantized first color component;
transform the perceptually quantized first color component, a perceptually quantized second color component, and a perceptually quantized third color component into a luma component and chroma components; and
subsampling the chroma components.
16 . The method of claim 15 , wherein the first color component of the pixel is green.
17 . The method of claim 15 , wherein spatially low-pass filtering the first color component of the pixel further comprises:
enabling and disabling the spatial low-pass filter based on a position, in a color gamut, of a point that corresponds to the first color component of the pixel, the second color component of the pixel, and the third color component of the pixel.
18 . The method of claim 15 , wherein spatially low-pass filtering the first color component of the pixel further comprises:
adjusting an amount of smoothing provided by the spatial low-pass filter based on a position, in a color gamut, of a point that corresponds to the first color component of the pixel, the second color component of the pixel, and the third color component of the pixel.
19 . The method of claim 15 , wherein spatially low-pass filtering the first color component of the pixel further comprises:
enabling the spatial low-pass filter based on the first color component of the pixel, the second color component of the pixel, and the third color component of the pixel corresponding to a point within a border region of a color gamut.
20 . The method of claim 15 , wherein spatially low-pass filtering the first color component of the pixel further comprises:
enabling the spatial low-pass filter based on the first color component of the pixel being below a first threshold and the second color component of the pixel being above a second threshold.
21 . A decoder, comprising:
a spatial low-pass filter configured to spatially smooth a luma component of a pixel to provide a filtered luma component;
a filter controller configured to enable and disable the spatial low-pass filter based on a position, in a color gamut, of a point that corresponds to a first color component of the pixel, a second color component of the pixel, and a third color component of the pixel,
an inverse decomposition transformation matrix configured to transform the filtered luma component and chroma components into color components; and
an inverse perceptual transfer function configured to inverse perceptually quantize the color components.