1、一個基于相鄰區塊相似性和動態次編碼簿的低位元率向量量化圖像壓縮法圖像壓縮法張真誠逢甲大學 講座教授清華大學 合聘教授中正大學 榮譽教授2圖像壓縮壓縮壓縮Alan1 0 1 0 0 1 0 1 1 0 0 10 1 0 1 0 0 1 0 1 1 1 01 0 0 1 0 1 1 1 0 0 0 01 0 1 0 0 0 0 1 0 1 1 13VQ (Vector Quantization)Index tablewhn壓縮ImageIndex table4ImageIndex tablewhVQ (Vector Quantization)n解壓縮Index tableCodebook 的長相6

2、SMVQ (Side Match Vector Quantization)Implementation of SMVQSeed BlockResidual Block7在在CB中找出最接近中找出最接近(67, 43, 96, 59, 47, x, x, x, 92, x, x, x, 40, x, x, x)的的codeword!(36+99)/2=678U13U14U15U16L4L8L12L16X1X2X3X4X5X9X13ULX找出最接近找出最接近(x1,x2,x3,x4,x5,x,x,x,x9,x,x,x,x13,x,x,x)的前的前 16 個個codewords，組成，組成 smal

3、ler codebook0 （）2125516-dim codewordCodebook0 （）2115SmallerCodebook9n解決Derailment(出軌) ProblemU13U14U15U16L4L8L12L16X1X2X3X4X5X9X13ULX0 （）2115SmallerCodebook計算原始圖的計算原始圖的block vector與與smaller codebook 之之 cw 的誤差的誤差 ErrorIf Error = Threshold，選擇，選擇 原始原始 codebook 的的index0 （）2125516-dim codewordCodebook001

4、0Error = TH1010001010CSMVQ (Classified Side-Match VQ)nCSMVQ uses two thresholds THc and THs.nTHc is used to choose size of a state codebook.nTHs is used to control the derailment problem.)var(;)var()var(;)var()var(, 4)var()var(, 2)var(, THcLTHcLTHcLTHcLandTHcUifhandTHcUorandTHcUifhandTHcUifh11State

5、codebooks(或稱 Smaller codebooks)Original codebook(或稱 Super codebook)h2h4hh12Proposed SchemenPCA (Principal Component Analysis)D1 = 0.710 0.703D2 = -0.703 0.71013Sorted CodebookCodebook D1: (0.5038, 0.4904, 0.4788, 0.5259) The projected valuesThe sorted codebookBlock 的分類nbasic block (B)none-neighbor r

6、eference blocks (1N)ntwo-neighbor reference blocks (2N)Sorting by PCASorted codebookB1N2NVQVQ2Ncodebook15Encodingn選用的Codebook Sizen對於 Basic Block (B) 永遠選用 Super CB。n對於 1N永遠選用 Size 為16 的Smaller CB。BULX1001012012:100101:2559293949596979899100101102103104105106107:CB012345678910111213141516BULX10010125

7、n對於2N考慮選用Size 為8的Smaller CB。(a) Encoding blocks(b) Encoded index tablediff = |cwU- cwL| = |102-104| = 2 TH1, 取出Smaller CB (Size 為8)Near cw = (102+104)/2 = 206/2 = 103。17012:103:255取出9910010110210310410510601234567在Smalle CB中找出 Best codeword 5若Distortion TH2, 則此cw 可用；否則要到Super CB 中找 best codeword。18D

8、ecodingn順序：1.Basic block (採用Super CB)2.1N reference block (採用Sized 16的Smaller CB)3.2N reference block (採用 Sized 8 的 Smaller CB or Super CB)Basic block1N2NVQ19Experimental results (a) Airplane (b) Lena (c) Toys (d) Baboon (e) Girl (f) Peppers Six test images of 512512 pixels 20AirplaneLenaToysBaboonG

9、irlPeppers0diff26661451292241312402348222diff52509218914661639236021615diff1526704205215336293768400315diff2512811852118924662015188125diff40978119873423081580115440diff606079184231991112380860diff256167716091194303815141554ImagesdiffnTable 1 針對2N之diff = | cwU - cwL|的分佈Table 2 各方法之比較22(a) Traditional VQ encoded30.905 dB0.5 bpp1.762 sec(b) CSMVQ encoded30.897 dB0.438 bpp4.236 secc) Proposed encoded30.823 dB0.363 bpp0.801 sec23結論nLower bit rate and