Separation And Simplification Of Codec And Its Window-based Coding For Display Stream Compression

With the rapid increase of the resolutions for display devices such as computers,televisions and mobile phones,it has become an consensus in industry to use display stream compression(DSC)technology to solve the problem of insufficient display link bandwidth.In recent years,various compression techniques for display link have been emerged,which include JPEG-XS,intra-coding only H.264/AVC,Dirac(VC-2),high efficiency video coding-screen content coding(HEVC-SCC)and DSC.Among them,the most typical solution is the DSC standard launched in 2014 by Video Electronics Standard Association(VESA).DSC is widely accepted low-cost,lowdelay and visual lossless light-weight video coding standard.The efficient coding techniques of DSC include advanced prediction,history color index(ICH),simplified entropy coding and excellent rate control.After a brief analysis of codec principles and stream syntaxs of DSC,this thesis researches on the practical application issues of DSC,so as to reasonably allocate resources and further reduce power consumption.Specifically,the main works and contributions are summarized as follows.Firstly,since both encoder and decoder are integrated together in the verification model of DSC,they are separated for possible proper simplification.In the reference codes or the verification model of DSC standard,both encoder and decoder are integrated together only for the purpose of principle verification.To put the DSC standard into practical uses,the first step is to separate encoder and decoder and optimize them separately.We found by analysis that most steps of encoder and decoder are almost the same,and they are inverse processes in them.That is,these steps can be separated for either encoder or decoder.Considering the fact that BMP is more commonly used for practical images than PPM,DPX,the support of BMP file as input and output is added.These works provide necessary foundation for the optimization of DSC codec.Second,to meet the requirements of local content refresh and further reduce the transmission bandwidth of display link,a slice-based window-based coding approach is proposed and implemented.Considering the fact that there exists partial refresh of screen contents in practical application,the slices that need to be refreshed are defined as a window.Then,window is regarded as the basic unit for both encodingand decoding,which makes data less,time shortened and power consumption reduced.AP catches the bitstream of the original big picture and the picture to be replaced,replaces the replaced picture bitstream to the big picture window position.Then we obtain the standard windowed DSC file by byte-based operations.We can also obtain standard un-windowed DSC file by byte operations from the bitstream of original picture stream.Finally,we send the windowed and unwindowed DSC file to decoder,and the correctness and feasibility of window-based coding are proved by making comparisons between the images before and after windowing.