融合全色度LZMA与色度子采样HEVC的屏幕图像编码
doi: 10.3724/SP.J.1146.2012.00746
Screen Content Coding by Combined Full-chroma LZMA and Subsampled-chroma HEVC
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摘要: 由于屏幕图像的各向异性特点,使用传统的图像/视频编码算法不能得到理想的编码效率。该文提出一种双编码器方案,在保留HEVC(High Efficiency Video Coding)对连续色调区域的优秀性能的同时,加入了从LZMA (Lempel-Ziv-Markov chain Algorithm) SDK中提取出来的对非连续色调区域编码性能更优的字典-熵编码模块。两种编码器以宏块级自适应的方式有机融合,可适应不同的视频源特性。为了减少YUV4:4:4格式转换到YUV4:2:0对图像造成的失真,该文还提出了混合色度采样率的设计,可在保留传统色度子采样编解码器和其低码率低成本优势特性的前提下,有效提高编码效率。实验结果表明,该文提出的方案,比单纯使用HEVC的性能提高约10~30 dB,其主观性能改善也非常明显。
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关键词:
- 高效视频编码 /
- Lempel-Ziv-Markov chain Algorithm (LZMA) /
- 屏幕图像编码 /
- 字典-熵编码器 /
- 混合色度采样率
Abstract: Considering the anisotropic characteristics of screen content, satisfactory coding efficiency cannot be achieved when screen content is coded only by traditional image/video coding tools. A new Dual-coder Mixed Chroma-sampling-rate (DMC) technique is proposed for full-chroma (YUV4:4:4) screen content coding by adding a dictionary-entropy based coder which extracted from Lempel-Ziv-Markov chain Algorithm (LZMA) to existing High Efficiency Video Coding (HEVC) SDK tools for better coding efficiency of discontinues-tone portion of screen content. Two coders are seamlessly unified and the optimal coder is selected adaptively macroblock-by-macroblock to fit the characteristics of the macroblock content. A mixed chroma-sample-rate method is also proposed for reducing distortions to convert YUV4:4:4 to YUV4:2:0. Coding experimental results show that DMC coding can achieve much higher PSNR than the current HEVC. There are also obvious improvements on the subjective visual quality differences between them.
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