cis679: jpeg (more)
DESCRIPTION
CIS679: JPEG (more). Review of JPEG More about JPEG Lab project. Review of JPEG. JPEG goals Picture Preparation Component, block, and pixel Picture Processing Shift Forward DCT Quantization Different coefficients are treated separately => quantization table. Differential Encoding. - PowerPoint PPT PresentationTRANSCRIPT
CIS679: JPEG (more)
Review of JPEG More about JPEG Lab project
Review of JPEG
JPEG goals Picture Preparation
Component, block, and pixel
Picture Processing Shift Forward DCT
Quantization Different coefficients are treated separately =>
quantization table
Differential Encoding
The DC coefficient varies only slowly from one block to the next. 12, 13, 11, 11, 10, ……
Only the difference in the preceding block is encoded. 12, 1, -2, 0. –1
Run-length Encoding
The AC coefficients are encoded in the form of a string of pairs of values (skip, value) (0,6)(0,7)(0,3)(0,3)(0,3)(0,2) (0,2)(0,2)(0,2)(0,0)
Huffman Encoding
Use variable length codes Most frequently used symbols coded with fewest bits The intermediate symbol sequence
DC coefficient: (sss, value)• sss: the number of bits needed• Value: the encode value
AC coefficient: (skip, sss) (value) with run-length encoding• skip: the number of consecutive 0• sss: the number of bits needed to encode the value• Value: the encode value
Huffman code DC coefficients: 12 = (4, 12) = (1011100) AC coefficient: (0, 6) = (0, 3) (6) = (100110)
Summary
DC coefficient Input: 12, 13, 11, 11, 10, …… Differential encode: 12, 1, -1,-1,-2… The intermediate symbol sequence: (sss, value) Huffman code:
• P160 (b) => sss• P160 (a) => value • Example: 12 = (4, 12) = (1011100)
AC coefficient Input: 6,7,3,0,0,3,3,2,0,0,0 Run-length encoding: (0,6)(0,7)(0,3)(2,3)(0,3)(0,2) (0,0) The intermediate symbol sequence: (skip, sss) (value) Huffman code:
• P163-164 => (skip, sss)• P160(a) => value• Example: (0, 6) = (0, 3) (6) = (100110)
Lab Project
Objective: be familiar with JPEG Description
Input: an original 8*8 block => original data (the value of each pixel is in the range of [0,255]) (given by the Instructor)
Steps:• Shifted to the range of [-128, 127]• FDCT (round: 1.6->2, -1.6->-2, 1.5->2, 1.1->1)• Quantized with the given quantization table (see the given
example) (round) (round: 1.6->2, -1.6->-2, 1.5->2, 1.1->1)• Zig-zag coded• Converted to the intermediate symbol sequence with run-
length encoding on AC coefficients• Encoded to bit sequence with Huffman encoding (based on the
given default Huffman codewords tables) => compressed data • The compression ratio = original data size (i.e. 64*8)/compressed data size
Output: print out all the results of the above steps into different files (The names and formats of output files should follow the files put on the web.)
Lab Project Team: one or 2 students What should be turned in (via email to [email protected]
state.edu, subject: 679 project)? Put all codes into one file (source_jpeg.c (.cpp) with clear comments
(softcopy)• Make sure TA can understand, compile, and run your codes on unix
machines. All the codes should be in C or C++. A report including a summary (2 <= page # <= 5) and the source
code file, and result files (hardcopy or softcopy either in PDF) Due date: Oct. 16, 2006, 5:00pm (EST) (both the code and the
report) How will TA grade?
Correctness: TA will use his own data to test your codes. Clearness: TA will check whether your code and report are
understandable. Fairness:
• Students in the same teams get the same scores.• No copy! All students involved in copy will get ZERO.
140 144 147 140 139 155 179 175
144 152 140 147 140 148 167 179
152 155 136 167 163 162 152 172
168 145 156 160 152 155 136 160
162 148 156 148 140 136 147 162
147 167 140 155 155 140 136 162
136 156 123 167 162 144 140 147
148 155 136 155 152 147 147 136
Example - Original Block
12 16 19 12 11 27 51 47
16 24 12 19 12 20 39 51
24 27 8 39 35 34 24 44
40 17 28 32 24 27 8 32
34 20 28 20 12 8 19 34
19 39 12 27 27 12 8 34
8 28 -5 39 34 16 12 19
20 27 8 27 24 19 19 8
Example - Shifted Block
186 -25 21 -13 33 -13 -20 -27
29 -34 27 -9 -11 11 14 7
-15 -23 -2 6 -18 3 -20 -1
-12 -5 15 -15 -8 -3 -3 8
-5 10 8 1 -11 18 18 15
5 -2 -18 8 8 -3 1 -7
12 1 -3 4 -1 -7 -1 -2
0 -8 -2 2 1 4 -6 0
Example -After FDCT
3 5 7 9 11 13 15 17
5 7 9 11 13 15 17 19
7 9 11 13 15 17 19 21
9 11 13 15 17 19 21 23
11 13 15 17 19 21 23 25
13 15 17 19 21 23 25 27
15 17 19 21 23 25 27 29
17 19 21 23 25 27 29 31
Example - Quantization Table
61 -5 3 -1 3 -1 -1 -2
6 -5 3 -1 -1 1 1 0
-2 -3 0 0 -1 0 -1 0
-1 0 1 -1 0 0 0 0
0 1 1 0 -1 1 1 1
0 0 -1 0 0 0 0 0
1 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Example - After Quantization
Example – Other StepsZig-zag sequence61,-5,6,-2,-5,3,-1,-3,-1,0,0,0,-1,3,3,-1,-1,0,1,1,0,1,0,1,-1,-1,1,-1,-2,1,3,0,0,-1,0,0,0,0,0,-1,0,-1,0,-1,0,1,0,0,0,0,0,0,1,0,1,0,0,0,0,0,0,0,0,0Intermediate symbol sequence(6)(61),(0,3)(-5),(0,3)(6),(0,2)(-2),(0,3)(-5), (0,2)(3), (0,1)(-1),(0,2)(-3),(0,1)(-1),(3,1)(-1), (0,2)(3), (0,2)(3),(0,1)(-1),(0,1)(-1), (1,1)(1), (0,1)(1),(1,1)(1), (1,1)(1), (0,1)(-1),(0,1)(-1),(0,1)(1),(0,1)(-1),(0,2)(-2),(0,1)(1),(0,2)(3),(2,1)(-1),(5,1)(-1),(1,1)(-1),(1,1)(-1),(1,1)(1),(6,1)(1),(1,1)(1),(0,0)Encoded bit sequence (total 154 bits)(1110)(111101) (100)(010) (100)(110) (01)(01) (100)(010) (01)(11) (00)(0) (01)(11) (01)(00) (00)(0) (111010)(0) (01)(11) (00)(0) (00)(0) (1100)(1) (00)(1) (1100)(1) (00)(0) (00)(0) (00)(1) (00)(0) (01)(01) (00)(1) (01)(11) (11011)(0) (1111010)(0) (1100)(0) (1100)(0) (1100)(1) (1111011)(1) (1100)(1) (1010)