Abstract: Since traditional video compressing tools are not suitable for screen contents,a lossy dictionary coding algorithm with adaptive matching error limit was proposed．After combining with full-chroma HEVC,a dual-coder scheme named LDSC(Lossy Dual-coder Single Chroma-sampling- rate) was obtained．According to the coding character of different types of area in screen content,better coding result was selected adaptively and put into bit-stream．To evaluate the performance of lossy string matching,we proposed the LD-Cost model based on the string matching length and distortion by employing lagrangian multiplier method．We also gave an elaborate analysis about the error accumulation phenomenon during lossy dictionary coding and pointed out a feasible way to avoid it．Experimental result show that the proposed method can obviously improve coding efficiency comparing with lossless dictionary coder based dual-coder scheme,and has better adaptability when coding discontinues-tone area of screen content．3%~15% coding gain can be achieved in BD-rate against lossless dictionary coder based dual-coder scheme in all- intra configuration．And the proposed method can obtain more BD-rate performance improvement,compared with latest HEVC reference software.

Key words: HEVC,LD-Cost,Screen content coding,Lossy dictionary coding