HW9_JPEG

HW9_JPEG - 0.0085 0.0044 0.0086 0.0046-0.0019 0.0036...

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Polytechnic University, Dept. Electrical and Computer Engineering EE3414 Multimedia Communication System I Spring 2006, Yao Wang __________________________________________________________________________________________________ Homework 9 (JPEG Image Coding) Written Assignment : 1. Describe briefly how JPEG compresses an image. You may want to break down your discussion into three parts: a. How does JPEG compress a 8x8 image block (three steps are involved) b. How does JPEG compress a gray-scale image c. How does JPEG compress a RGB color image 2. Describe what does a scalable bit stream mean and why is scalability a desired feature for image coding and transmission. What is the difference between quality scalability and spatial scalability? 3. Suppose the DCT coefficient matrix for an 4x4 image block is as shown below ( dctblock ). a. Quantize its DCT coefficients using the quantization matrix Q given below, assuming QP=1. Determine the quantized coefficient indices and quantized values.
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Unformatted text preview: , 0.0085 0.0044 0.0086 0.0046-0.0019 0.0036 0.0207-0.0086-0.0071 0.0877 0.0033-0.0134 0.0912 0.0466-0.0500-1.3676 * 003 . 1 + = e dctblock , 120 103 78 49 103 68 37 18 69 40 16 14 51 24 10 16 = Q b. Represent the quantized indices using the run-length representation. That is, generate a series of symbols, the first being the quantized DC index, the following symbols each consisting of a length of zeros and the following non-zero index, the last symbol is EOB (end of block). c. Encode the DC index and the runlength symbols from (b) using the JPEG coding method, with the coding tables given in the lecture note. For this problem, assuming the quantized index for the DC coefficient of the previous block is 60. 4. Determine the Y,Cr,Cb values for a pixel with (R,G,B) value of R=200,G=150, B=50....
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