摘要:
A processor for signal reshaping receives an input image with an input bit depth. Block-based standard deviations are computed. The input codewords are divided into codeword bins and each bin is assigned a standard deviation value. For each bin, a standard deviation to bit-depth function is applied to the bin values to generate minimal bit depth values for each codeword bin. An output codeword mapping function is generated based on the input bit depth, a target bit depth, and the minimal bit depth values. The codeword mapping function is applied to the input image to generate an output image in the target bit depth.
摘要:
An encoder receives an input enhanced dynamic range (EDR) image and a corresponding lower dynamic range (LDR) image to be coded at a given target rate. Before coding, a pre-dithering process is applied to the input LDR image to generate a dithered LDR image at a second bit depth, lower than its original bit depth. The pre-dithering process includes: generating uniformly-distributed noise, applying a spatial filter to the noise to generate low-pass or high-pass filtered noise, applying a temporal high pass or low pass filter to the spatially-filtered noise to generate output noise, adding the output noise to the input LDR image to generate a noise-enhanced LDR image, and quantizing the noise-enhanced image to generate the dithered LDR image. Selecting the characteristics of the dithering filters is based on both the target bit rate and luminance characteristics of the pixels in the input LDR image.
摘要:
In high-dynamic range (HDR) coding, content mapping translates an HDR signal to a signal of lower dynamic range. Coding and prediction in layered coding of HDR signals is improved if content mapping utilizes signal color ranges beyond those defined by a traditional electro-optical transfer function (EOTF) or its inverse (IEOTF or OETF). Extended EOTF and IEOTF functions are derived based on their mirror points. Examples of extended EOTFs are given for ITU BT. 1886 and SMPTE ST 2084.
摘要:
A set of optimized operational parameter values is generated for performing decontouring operations on a predicted image. The predicted image is predicted from a first image mapped from a second image that has a higher dynamic range than the first image. Based on the set of optimized operational parameter values, smoothen operations and selection/masking based on a residual mask are performed on the predicted image. The set of optimized operational parameter values is encoded into a part of a multi-layer video signal that includes the first image, and can be used by a recipient decoder to generate a decontoured image based on the predicted image and reconstruct a version of the second image.
摘要:
A sequence of visual dynamic range (VDR) images is encoded using a standard dynamic range (SDR) base layer and one or more enhancement layers. A predicted VDR image is generated from an SDR input by using a weighted, multi-band, cross-color channel prediction model. Exponential weights with an adaptable decay parameter for each band are also presented.
摘要:
Error control in multi-stream visual dynamic range (VDR) codecs is described, including for a case of a layer-decomposed (non-backward compatible) video codecs. Error control can be provided by concealing lost and/or corrupted data in data frames of a decoded VDR bitstream prior to rendering a corresponding VDR image. Various algorithms and methods for concealing lost and/or corrupted data are provided.
摘要:
An encoder receives an input enhanced dynamic range (EDR) image to be coded in a layered representation. Input images may be gamma-coded or perceptually-coded using a bit-depth format not supported by one or more video encoders. The input image is remapped to one or more quantized layers to generate output code words suitable for compression using the available video encoders. Algorithms to determine optimum function parameters for linear and non-linear mapping functions are presented. Given a mapping function, the reverse mapping function may be transmitted to a decoder as a look-up table or it may be approximated using a piecewise polynomial approximation. A polynomial approximation technique for representing reverse-mapping functions and chromaticity translation schemes to reduce color shifts are also presented.
摘要:
An encoder receives a target image in a standard dynamic range and a guide image in a high dynamic range, wherein both the target image and the guide image represent the same scene. A color transient improvement (CTI) filter is selected to predict a chroma component of a decoded version of the target image based on both the luma and chroma components of the target image and the guide image. The filtering coefficients for the CTI filter are computed by minimizing an error measurement (e.g., MSE) between pixel values of the decoded image and the guide image. The computed set of filtering coefficients is signaled to a receiver (e.g., as metadata). A decoder receives the coded image and the metadata, and applies the same CTI filter to the decoded image to generate an output image.
摘要:
An encoder receives one or more input pictures of enhanced dynamic range (EDR) to be encoded in a coded bit stream comprising a base layer and one or more enhancement layer. The encoder comprises a base layer quantizer (BLQ) and an enhancement layer quantizer (ELQ) and selects parameters of the BLQ and the ELQ by a joint BLQ-ELQ adaptation method which given a plurality of candidate sets of parameters for the BLQ, for each candidate set, computes a joint BLQ-ELQ distortion value based on a BLQ distortion function, an ELQ distortion function, and at least in part on the number of input pixels to be quantized by the ELQ. The encoder selects as the output BLQ parameter set the candidate set for which the computed joint BLQ-ELQ distortion value is the smallest. Example ELQ, BLQ, and joint BLQ-ELQ distortion functions are provided.
摘要:
Error control in multi-stream visual dynamic range (VDR) codecs is described, including for a case of a layer-decomposed (non-backward compatible) video codecs. Error control can be provided by concealing lost and/or corrupted data in data frames of a decoded VDR bitstream prior to rendering a corresponding VDR image. Various algorithms and methods for concealing lost and/or corrupted data are provided.