23-07-2014, 10:46 AM
Video Compression Technique Using
Wavelet Transform
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Abstract
- A new approach to video
compression is presented which is based on
the use of the wavelet transform and a
differential image compression technique. The
algorithm combines the scale reduction
capabilities of the wavelet transformi with the
data reduction capabilities of the dlifferential
image compression. Experimental results of
applying the differential wavelet transform at
different threshold levels to a computer
generated animated sequence are presented.
INTRODUCTION
the past few years there has been an
increased interest -in the areas of video
compression, video telephony, and
videoconferencing. This is partly due to the
technology breakthroughs in digital computer
industry, application specific integrated
circuits, and increase in storage media. Even
with all of the advances in technology, the
world of video images demand much more.
For example the amount of time that takes to
transmit a 5000x6000 radiograph picture using
the newly emerging fiber optics distributed
data interchange (FDDI), which provides
communication at a rate of 100 Mbitsh, is
about 15 secondpicture assuming an
optimistic 20% through rate for a shared
network. However, in many applications it is
desired to access the image in less than 2
seconds. The desired time can be achieved by
compressing data at a rate of 7.5:l.
. D~RENCIA~ IMAGE COMPRESSION
The differential image compression algorithm
@ICA),[3], is based on the concept of
retaining/transmitting only the difference
between frame images. The algorithm takes
advantage of the similarities between frame
images. For instance, consider the technology
of videoconferencing and how the background
of the images remain virtually the same
throughout the communication session.
Rather than transmitting the background
information for every frame, the DICA only
transmits the background information for the
first frame and then sends only thle changes
between subsequent frames. This technique
has been used for many years.
Bitmap encoding of differential images is an
encoding technique whereby a table of single
bits is used to represent each pixel of a frame.
If a pixel changed values from the previous
frame, then a 1 would be place in the
corresponding location of the bit table. If a
pixel value does not change, then a 0 is placed
in the corresponding location of the bit table.
Each time a 1 is replaced in the bit table, the
new pixel value is appended to a stream of
changed values. Consequently, the coder
transmits the bit table as well as the stream of
changed data values. The receiving unit
matches the 1’s in the bit table to the new
pixel values in order to display the next frame
CONCLUSIONS
It is learned that the differential wavelet
transform algorithm can be employed to
reduce the amount of data required to
transmit video images. The highest
compression ratio achieved by this method
without visible degradation was 72: 1.
This compression ration is comparable and
in some cases better than the PEG, The highest
compression ratio achieved by this method
without visible degradation was 72: 1.
This compression ration is comparable and
in some cases better than the PEG,