1. MPEG-1 Video Coding Standard
Jianping Fan
Department of Computer Science
University of North Carolina at Charlotte
Charlotte, NC 28223

2. 1. What does MPEG mean?
MPEG: Moving Picture Experts Group
2. Why we do not use MJPEG? 12 13 14
Spatial correlations among neighboring pixels!
Temporal correlations among neighboring frames!

3. 3. Why we need MPEG?
Temporal Redundancy
Exploit temporal relationship among frames for coding!
save our money for: a. Storage space;
b. Bandwidth
CIF: 352*288
MPEG
Frame rate: 25f/s
1.5Mbits/s
Space: ~21.6Mbits/s

4. 4. MPEG Video Structure
Temporal relationships could be in short period!
GOP 1
GOP 2
GOP 3
GOP 4
time
Why we need this? I B B P B B P B B B P
GOP

5. 4. MPEG Video Structure
16*16
8*8
block
macroblock
frame
Universal structure is very important for universal decoder!!

6. 5. MPEG-1 Encoder
MPEG-1 has defined three frame coding types: I, P, B.
I frame: Intra-coding frame
P frame: motion-based predictive coding frame
B frame: motion-based bidirectional predictive coding frame
The difference between I and P or B:
I can be encoded/decoded without reference
The difference between P and B:
P can be encoded/decoded with one reference

7. 5. MPEG-1 Encoder
DCT Q
VLC
Buffer
01001…. IQ
Q: quantization ME
IDCT
IDCT IQ
VLC
Buffer
01001….
ME: motion estimation ME
IQ: reverse quantization

8. 5. MPEG-1 Encoder I B P

9. 6. How to Encode I Frame? slice Y DCT U V Entropy coding
block
DCT U V
macroblock
Entropy coding
…………

10. (3) CIE: more close to human vision
6. How to Encode I Frame?
a. Color Space
(1) RGB: display
(2) YUV: coding
(3) CIE: more close to human vision
b. DCT (Discrete Cosine Transformation)
DCT

11. b. DCT (Discrete Cosine Transformation)
6. How to Encode I Frame?
b. DCT (Discrete Cosine Transformation)
DCT

12. Q(u) = integer round (u/scale)
6. How to Encode I Frame?
DCT
Zigzag scale
Quantization
(7,0), (5,0), (2,0), (2,0), (3,4), (1,4), (1,41)
Q(u) = integer round (u/scale)
Entropy coding

13. 6. How to Encode I Frame?

14. 6. How to Encode I Frame?
Entrpoy coding:
Code
probability 1 1
Pc=1/2 1 01
Pc=1/4 1
001
Pc=1/8
000
Pc=1/8
Huffman Tree

15. 7. How to Encode P Frame?
Motion-based prediction
I or P frame
Current P frame
I B B P B B P B B P

16. 7. How to Encode P Frame?
Motion compensation: motion vectors + errors

17. a. Find the reference block at the same position
7. How to Encode P Frame?
Motion estimation:
a. Find the reference block at the same position
(x,y)
(x,y)
Reference Frame
Current Frame
I, P blocks & Skip

18. 7. How to Encode P Frame?
b. Take the reference block as the search center

19. 8. How to Encode B Frame?
Forward prediction
Backward prediction
Previous reference
Current frame
Future reference
I B B P B B P

20. 8. How to Encode B Frame?
Why we need B frame?
Higher compression ratio
I, P, B blocks & Skips

21. 8. How to Encode B Frame?
Why we cannot put too much B frames?
Display order:
I B B P B B P B B P B B P
Encoding order:
I P B B P B B P B B P B B
Buffer Size: 3 frames

22. 9. How to Design MPEG Decoder?
Video sequence
Sequence header
Sequence end code
Sequence layer
GOP
GOP
GOP
GOP
GOP header
GOP layer
I-frame
P-frame
B-frame
B-frame
Picture header
slice
slice
slice
Picture layer
Slice header
macroblock
macroblock
Slice layer
Macroblock header
Macroblock layer
Block(0)
Block(1)
Block(5)

23. 9. How to Design MPEG Decoder?
a. Search for the start codes:
Sequence header code: 0x000001B bits
Sequence end code: x000001B bits
Group_start_code: x000001B bits
Picture_start_code: x bits
Slice_start_code: x000001AF bits

24. 9. How to Design MPEG Decoder?
b. Functions for decoding the video data:
Sequence header()
Sequence_start_code 32
Horizontal size 12 12
Vertical size 4
Pel_aspect_ratio 4
Picture_rate 18
Bit rate
Marker_bit 1
Buffer_size 10
Q table 22
Quantization table
Done

25. 9. How to Design MPEG Decoder?
Group_of_picture ()
Group_start_code 32
Drop_frame_flag 1
Time_code_hours 5
Time_code_minutes 6
Market_bit 1
Time_code_seconds 6 6
Time_code_pictures
Close_gop 1 1
Broken_link
Picture( )
Done

26. 9. How to Design MPEG Decoder?
Picture ( ) 32
Picture_start_code 10
Temporal_reference 3
Picture_coding_type 16
Decoding_delay 3
Forward_vector_type 3
Backward_vector_type
Slice( )
Done

27. 9. How to Design MPEG Decoder?
Slice ( ) 32
Slice_start_code 5
Quantization scale
Macroblock ( )
Done

28. 9. How to Design MPEG Decoder?
Macroblock ( ) 11
Macroblock_escape
Macroblock_address_increase
1-11
Macroblock_type
1-6 5
Quantizer_scale
Motion_vector ( )
3-9
Coded_block_pattern
Block (i)
Done

29. 10. Where you can find MPEG? a. b.
Question:
If you are offered a job on designing MPEG decoder, how you can do?
Show me the video frames from 1228 to 1338?
IBM, Microsoft, Intel, NEC, Cisco, Eastman Kodak, ……, .com