激光与光电子学进展, 2018, 55(7): 071001, 网络出版: 2018-04-01

HEVC-SCC自适应调色板模式快速决策算法

HEVC-SCC Adaptive Palette Mode Fast Decision Algorithm
作者单位

天津大学微电子学院, 天津 300072

摘要
随着图像内容不断丰富,由计算机产生的屏幕内容(SC)图像开始普及。针对这类图像,高效视频编码标准(HEVC)增加了调色板模式来提升对SC图像的压缩性能,但会增加计算复杂度和编码时间。提出了一种基于视频内容复杂度分析的自适应调色板模式快速决策算法。该算法将图像亮度分量分块,并用离散余弦变换(DCT)来衡量每个块的复杂度,然后根据复杂度值形成判别矩阵,最后根据判别矩阵结合编码单元的信息来自适应地关闭或启用调色板模式,以减少计算量和编码时间。根据实验结果,当参考编码器设为启用调色板模式时,本文算法能节省的总编码时间达到完全关闭调色板模式所节省时间的69.24%,而相同峰值信噪比下的码率差异(BDBR)平均增加0.33%,相同码率下的峰值信噪比差异(BDPSNR)平均下降0.03 dB,基本不影响视频质量。
Abstract
With the development of the image content, screen content (SC) images generated by computers begin to spread. In order to code the screen content more efficiently, a new tool named palette mode is added into the High Efficiency Video Coding (HEVC) to improve the compression performance, but it will greatly increase the computational complexity and coding time. We propose an adaptive palette mode decision algorithm based on the complexity analysis of the video content. The proposed algorithm divides the luminance component of the image into blocks and applies discrete cosine transform (DCT) to measure the complexity of each block. Then a judge matrix is derived based on the complexity values. Finally, the coding unit information and the judge matrices are used to judge whether to enable or disable the palette mode. According to the experimental results, compared with the anchor encoder that enables the palette mode, the total encoding time saving of the proposed algorithm can reach 69.24% of the total encoding time saving when the palette mode is disabled, with averagely 0.33% of the bjntegaard delta bit rate (BDBR) increase and 0.03 dB of the bjntegaard delta peak signal-to-noise ratio (BDPSNR) decrease.
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