On a Wavelet-based Image Compression System
Tzu-Hong Cheng and C. H. Chen
University of Massachusetts Dartmouth
Abstract
The increased demand for sending images/videos requires us to make more
efficient use of communication bandwidth by reducing the amount of
information transmitted on the channel (compression). This image
compression problem has now been one of the major problem areas in modern
telecommunications systems.
The conventional approach of using DCT compression (discrete cosine
transform) which is Fourier based has been most popular in industry as it
is the standard for JPEG and MPEG2. An image has to be divided into blocks
of suitable size in DCT compression. The result is an undesirable
image-degradation blocking artifacts. In wavelet-based compression, the
entire image can be filtered without being broken into blocks, and thus
eliminating the blocking effect.
In this paper a new wavelet-based image compression system is proposed
that offers a large compression ratio and thus greatly increases the
efficiency of bandwidth utilization. The software algorithm employed is
based on a modification of the 3-D subband coding algorithm developed by
Podilchuk et al. such that a sequence of images is encoded at the same
time, by using the knowledge that the scenes vary very slightly from one
image to the next. The exploitation of contexts in both space-time and
space-space brings out an improved compression algorithm that is both
performance effective and computationally efficient. The decompression
result is shown to exceed the performance offered by available image
compression boards. The software based system has the advantage that it is
much more flexible and less costly than hardware systems.
To test the approach we have examined the compression of video images
of a traffic scene for the intelligent transportation systems with
satisfactory results.
Tzu-Hong Cheng
Electrical and Computer Engineering Dept.
University of Massachusetts Dartmouth
285 Old Westport Road
North Dartmouth, MA 02747-2300
C. H. Chen
Electrical and Computer Engineering Dept.
University of Massachusetts Dartmouth
285 Old Westport Road
North Dartmouth, MA 02747-2300
Tel: 508-999-8475
cchen@umassd.edu