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Unformatted text preview: the resulting data is called compressed data. The reverse
process of reproducing the original data from compressed data is called
decompression and the resulting data is called decompressed data. We will see
below that the decompressed data may or may not be the same as the original data
depending on the type of compression technique used.
Types of Compression Techniques
Compression techniques can be categorized based on the following considerations:
1. Lossless or lossy. If the decompressed data is the same as the original data, it
is referred to as lossless compression, otherwise the compression is lossy because
there is loss of originality in the reproduced data. Lossy compression techniques
usually have higher compression ratios (larger reduction in the volume of data),
but may introduce some distortion in the original quality of the data when
decompressed. In case of lossy compression, the desired quality level of the
decompressed data is application dependent.
Symmetrical or asymmetrical. In a compression technique, if the time
required to compress and to decompress are roughly the same, it is referred to as
symmetrical compression. In asymmetrical compression, the time taken for
compression is usually much
longer than decompression. Symmetrical
techniques are used in those applications that require data to be digitized and
compressed in real time, such as video conferencing. On the other hand,
asymmetrical techniques are used in those applications in which the data are
compressed once and decompressed several time, such as in video-on-demand
3. Software or hardware. A compression technique may be implemented either
in hardware or software. As compared to software codecs (COder and DECoder),
hardware codecs offer better quality and performance. However, they are costlier
and are available only on platforms with costly extended hardware.
codecs can be ported on any platform ensuring wider consumer accessibility. Due
to performance reason, hardware codecs are suitable for CPU-intensive processing
and software codecs are suitable for less CPU-intensive processes. Basic Compression Techniques
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- Spring '14