Screen Content Coding with Primary and Secondary Reference Buffers for String Matching and Copying

A screen content coding （SCC） algorithm that uses a primary reference buffer （PRB） and a secondary reference buffer （SRB） for string matching and string copying is proposed. PRB is typically the traditional reconstructed picture buffer which provides reference string pixels for the current pixels being coded. SRB stores a few of recently and frequently referenced pixels for repetitive reference by the current pixels being coded. In the encoder, searching of optimal reference string is performed in both PRB and SRB, and either a PRB or SRB string is selected as an optimal reference string on a string-by-string basis. Compared with HM-16.4＋SCM-40 reference software, the proposed SCC algorithm can improve coding performance measured by bit-distortion rate reduction of average 4.19% in all-intra configuration for text and graphics with motion category＇ of test sequences defined by JCT-VC common test condition.