ITM(inverse tone-mapping) converts SDR (standard dynamic range) footage to
HDR/WCG (high dynamic range /wide color gamut) for media production. It happens
not only when remastering legacy SDR footage in front-end content provider, but
also adapting on-theair SDR service on user-end HDR display. The latter
requires more efficiency, thus the pre-calculated LUT (look-up table) has
become a popular solution. Yet, conventional fixed LUT lacks adaptability, so
we learn from research community and combine it with AI. Meanwhile,
higher-bit-depth HDR/WCG requires larger LUT than SDR, so we consult
traditional ITM for an efficiency-performance trade-off: We use 3 smaller LUTs,
each has a non-uniform packing (precision) respectively denser in dark, middle
and bright luma range. In this case, their results will have less error only in
their own range, so we use a contribution map to combine their best parts to
final result. With the guidance of this map, the elements (content) of 3 LUTs
will also be redistributed during training. We conduct ablation studies to
verify method's effectiveness, and subjective and objective experiments to show
its practicability. Code is available at: this https URL

通过将传统的固定 LUT 与人工智能相结合，引入非均匀打包的解决方案来使得 SDR 素材转换为 HDR/WCG，同时根据偏重范围密度的三个小型 LUT 结果，通过贡献度图进行组合，从而实现更高效的适配性和性能平衡。

基于 3D-LUT 的 HDR/WCG 显示器逆色调映射中的精度和内容重分配

Redistributing the Precision and Content in 3D-LUT-based Inverse  Tone-mapping for HDR/WCG Display

Joint learning of super-resolution (SR) and inverse tone-mapping (ITM) has
been explored recently, to convert legacy low resolution (LR) standard dynamic
range (SDR) videos to high resolution (HR) high dynamic range (HDR) videos for
the growing need of UHD HDR TV/broadcasting applications. However, previous
CNN-based methods directly reconstruct the HR HDR frames from LR SDR frames,
and are only trained with a simple L2 loss. In this paper, we take a
divide-and-conquer approach in designing a novel GAN-based joint SR-ITM
network, called JSI-GAN, which is composed of three task-specific subnets: an
image reconstruction subnet, a detail restoration (DR) subnet and a local
contrast enhancement (LCE) subnet. We delicately design these subnets so that
they are appropriately trained for the intended purpose, learning a pair of
pixel-wise 1D separable filters via the DR subnet for detail restoration and a
pixel-wise 2D local filter by the LCE subnet for contrast enhancement.
Moreover, to train the JSI-GAN effectively, we propose a novel detail GAN loss
alongside the conventional GAN loss, which helps enhancing both local details
and contrasts to reconstruct high quality HR HDR results. When all subnets are
jointly trained well, the predicted HR HDR results of higher quality are
obtained with at least 0.41 dB gain in PSNR over those generated by the
previous methods.

本文提出了一种基于生成对抗网络的分组超分辨率和反色调映射联合学习模型，通过精心设计包括图像重建子网、细节恢复子网和局部对比度增强子网等三个任务特定子网，训练一对 1D 可分离细节恢复像素滤波器和一个局部对比度增强 2D 滤波器，以提高本文模型处理 HDR 图像过程中所需的超分辨率和反色调映射性能，实验证明该模型能够比之前的方法提高 0.41 dB 的 PSNR 值。