文档介绍：Topic-3:Still Image Coding Standard
Several typical image/pression coding standard
、:TV Conference and Visual Telephone System;
JPEG、JPEG2000:Still pression;
MPEG-1: VCD;
MPEG-2: DTV、DVD、HDTV;
MPEG-4: munication。
JPEG standard
JPEG (Joint Photographic Experts Group)
Reducing the size of photographic images or continuous-tone artwork – pictures
pression can be performed on 24-bit color or 8-bit grayscale images.
pression Arithmetic
DCT: pression
Predictive coding : pression
JPEG image reconstruction mode:
Sequential decoding (line-by-line) ;
Progressive decoding (refinement of the whole image)
Four different modes
Lossy Sequential DCT based mode
Baseline process that must be supported by every JPEG implementation.
Expanded Lossy DCT based mode
enhancements to baseline process
Lossless mode
pression ratio
allows perfect reconstruction of original image
Hierarchical mode
odate images of different resolutions
JPEG coding system
The baseline process
The extended process
Diagram of DCT encode and decode
Original image data
Rebuild image data
DCT
IDCT
Quantizer
Re-quantize
Quantize table
Entropy encode
Entropy decode
Code output
channel
8×8 sub MB
8×8 sub MB
f(x,y)
f’(x,y)
F(u,v)
F’(u,v)
S(u,v)
Q(u,v)
Q(u,v)
Original image sub MB brightness value
Relative DCT coefficients
The quantization coefficients
The inverse quantization coefficients