标题： 无损4:2:0屏幕内容编码使用亮度引导的软上下文生成 显示英文标题

标题： Lossless 4:2:0 Screen Content Coding Using Luma-Guided Soft Context Formation

摘要： 软上下文形成编码器是一种使用模式匹配和颜色调色板编码相结合的逐像素最先进的无损屏幕内容编码器，以及算术编码。 它在具有少量不同颜色的RGB 4:4:4格式的屏幕内容图像上实现了出色的压缩性能。 与许多其他无损压缩方法不同，它一次对整个颜色像素进行编码，即一个像素的所有颜色分量一起进行编码。 因此，它不原生支持下采样色度的图像格式，例如YCbCr 4:2:0，这是视频压缩中常用的色度格式。 在本文中，我们通过依次编码Y和CbCr平面来扩展软上下文形成编码能力，以实现4:2:0图像压缩，基于对图像平面之间归一化互信息的分析。 此外，我们提出了一种基于亮度平面的色度预测增强方法。 此外，我们建议传输关于出现的亮度-色度组合的辅助信息，以改善色度概率分布建模。 在大量屏幕内容图像数据集上平均，我们的方法优于HEVC-SCC，与我们的方法相比，HEVC-SCC需要多5.66%的比特率。 显示英文摘要

摘要： The soft context formation coder is a pixel-wise state-of-the-art lossless screen content coder using pattern matching and color palette coding in combination with arithmetic coding. It achieves excellent compression performance on screen content images in RGB 4:4:4 format with few distinct colors. In contrast to many other lossless compression methods, it codes entire color pixels at once, i.e., all color components of one pixel are coded together. Consequently, it does not natively support image formats with downsampled chroma, such as YCbCr 4:2:0, which is an often used chroma format in video compression. In this paper, we extend the soft context formation coding capabilities to 4:2:0 image compression, by successively coding Y and CbCr planes based on an analysis of normalized mutual information between image planes. Additionally, we propose an enhancement to the chroma prediction based on the luminance plane. Furthermore, we propose to transmit side-information about occurring luma-chroma combinations to improve chroma probability distribution modelling. Averaged over a large screen content image dataset, our proposed method outperforms HEVC-SCC, with HEVC-SCC needing 5.66% more bitrate compared to our method.