Compress compound images in H.264/MPEG-4 AVC by fully exploiting spatial correlation
Compress compound images in H.264/MPEG-4 AVC by fully exploiting spatial correlation
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DOI：
10.1109/iscas.2009.5118388
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发表时间：
2009-05
期刊：
影响因子：
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通讯作者：
Cuiling Lan;Feng Wu;Guangming Shi
中科院分区：
文献类型：
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作者：
Cuiling Lan;Feng Wu;Guangming Shi
复合图像由文本、图形和自然图像组成，呈现出强烈的各向异性特征。它使得现有的图像编码标准在压缩方面效率低下。针对这一问题，本文提出了一种基于H.264帧内编码的新编码方案。提出了两种新的帧内模式，以更好地利用复合图像中的空间相关性。第一种是残差标量量化 (RSQ) 模式，其中直接对帧内预测残差进行量化和熵编码。第二种是基色和索引图 (BCIM) 模式，可以将其视为自适应矢量量化。在这种模式下，图像块由几种代表颜色（称为基色）和要压缩的索引图表示。 H.264 中的两种新模式以及以前的帧内模式是通过每个块中的率失真优化 (RDO) 方法选择的。实验结果表明，该方案不仅对复合图像的编码效率提高了10dB以上，而且对自然图像也保持了与H.264相似的性能。
Compound images consist of text, graphics and natural images, which present strong anisotropic features. It makes existing image coding standards inefficient on compressing them. To solve the problem, this paper proposes a novel coding scheme based on the H.264 intra-frame coding. Two new intra modes are proposed to better exploit spatial correlations in compound images. The first is residual scalar quantization (RSQ) mode, where intra-predicted residues are directly quantized and entropy coded. The second is base colors and index map (BCIM) mode that can be viewed as an adaptive vector quantization. In this mode, an image block is represented by several representative colors, called as base colors, and an index map to compress. Two new modes as well as previous intra modes in H.264 are selected by the rate-distortion optimization (RDO) method in each block. Experimental results show that the proposed scheme not only improves the coding efficiency even more than 10dB for compound images but also keeps the similar performance as H.264 for natural images.