Video Processing Technology
multimedia data requires considerable storage capacity and transmission bandwidth.
Despite rapid progress in mass storage density processor speeds and digital communication
system performance, demand for data storage capacity and data transmission bandwidth
continues to outstrip the capabilities of available technologies. The recent growth
of data intensive multimedia-based web applications have not only sustained the
need for more efficient ways to encode signals and images but have made compression
of such signals central to storage and communication technology.
For still image compression, the joint photographic experts group (JPEG) standard
has been established. The performance of these codes generally degrades at low
bit rates mainly because of the underlying block-based Discrete cosine Transform
(DCT) scheme. More recently, the wavelet transform has emerged as a cutting edge
technology, within the field of image compression. Wavelet based coding provides
substantial improvements in picture quality at higher compression ratios. Over
the past few years, a variety of powerful and sophisticated wavelet based schemes
for image compression have been developed and implemented. Because of the many
advantages, the top contenders in JPEG-2000 standard are all wavelet based compression
Image compression is a technique for processing images. It is the compressor of
graphics for storage or transmission. Compressing an image is significantly different
than compressing saw binary data. Some general purpose compression programs can
be used to compress images, but the result is less than optimal. This is because
images have certain statistical properties which can be exploited by encoders
specifically designed for them. Also some finer details in the image can be sacrificed
for saving storage space.
Compression is basically
of two types.
1. Lossy Compression
2. Lossless Compression.
Lossy compression of data concedes a certain loss of accuracy in exchange for
greatly increased compression. An image reconstructed following lossy compression
contains degradation relative to the original. Often this is because the compression
scheme completely discards redundant information. Under normal viewing conditions
no visible is loss is perceived. It proves effective when applied to graphics
images and digitized voice.
Lossless compression consists of those techniques
guaranteed to generate an exact duplicate of the input data stream after a compress
or expand cycle. Here the reconstructed image after compression is numerically
identical to the original image. Lossless compression can only achieve a modest
amount of compression. This is the type of compression used when storing data
base records, spread sheets or word processing files.
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