电子科技女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC Examaple8.1 A simple illustration of variable-length coding Tk p() Code 1 1i(rk) Code 2 12(k) r87=87 0.25 01010111 8 01 2 128=128 0.47 10000000 8 1 1 186=186 0.25 11000100 8 000 3 255=255 0.03 11111111 8 001 3 rk for k≠87,128,186,255 0 8 0 4 256×256×8 1)P) C= ≈4.42 k=0 256×256×1.81 =2(0.25)+1(0.47)+3(0.25)+3(0.03) =1.81bit R=11 =0.774 4.424 0 () () 2(0.25) 1(0.47) 3(0.25) 3(0.03) 1.81 bit avg k r k k L lr P r       1 1 0.774 4.42 R   Examaple8.1 A simple illustration of variable-length coding 256 256 8 4.42 256 256 1.81 C      