data compression.

1. “𝐻𝑒𝑎𝑣𝑒𝑛’𝑠 𝐿𝑖𝑔ℎ𝑡 𝐼𝑠 𝑂𝑢𝑟 𝑮𝒖𝒊𝒅𝒆”
Rajshahi University of Engineering &
Technology
Department of Electronics and
Telecommunication Engineering

2. Information Theory
ETE 315
Submitted to –
Sham Datto
Lecturer : Dept. of ETE
Submitted by -
Hasan Sarkar
Roll: 114041

3. Content of information encoding:
 1. Source coding or bit-rate reduction
 2. Digital signal processing &
 3. Data compressions

4. Topics :
 1. (a) Compression of information.
(b) information content of compressed
data &
 2. continuous amplitude signals.

5. 1. Compression of information
 WHAT IS COMPRESSION?
 Compression is the process of reducing the size of a file by
encoding its data information more efficiently.
 the result is a reduction in the number of bits and bytes
used to store the information.
 In effect, a smaller file size is generated in order to
achieve a faster transmission of electronic files and a
smaller space required for its downloading.

6. Data without compression

7. Data with compression
Compression
technique

8. Why is data compression
needed?
1. Data compression is needed because it allows the data to be
stored in an area without taking up an unnecessary amount of
space.
2. a smaller file size is generated in order to achieve a faster
transmission and downloading.
3. It reduces redundant information by using different and more
efficient ways of representing the information.

9. Types of data compression
 According to Loss :
1. Lossless compression.
2. Lossy compression.
 According to compression rate:
1. Low rate compression.
2. High rate compression.

10. Lossless compression :
With lossless compression, every single bit of data that was originally in the file
remains after the file is uncompressed.
Lossy compression :
lossy compression reduces a file by permanently eliminating certain information,
especially redundant information.

11. Low and high (quality) compression :
Low compression (high quality) High compression (low quality)

12. How does compression work ?
 When you have a file containing text, there can be repetitive single
words, word combinations and phrases Or there can be media such as high
tech graphical images . To reduce this inefficiency electronically, you can
compress the document.
 Compression is done by using compression algorithms (formulae) that
rearrange and reorganize data information so that it can be stored more
economically.
 By encoding information, data can be stored using fewer bits. This is
done by using a compression/decompression program that alters the
structure of the data temporarily for transporting, reformatting,
archiving, saving, etc.
 Methods may include simply removing space characters, using a single
character to identify a string of repeated characters, or substituting
smaller bit sequences for recurring characters.

13. Compression ratio :
the size of the compressed file compared
to that of the uncompressed file -
 Video can be compressed immensely (e.g. 100:1) with little
visible quality loss
 Audio can often be compressed at 10:1 with imperceptible
loss of quality
 Still images are often lossily compressed at 10:1, as with
audio, but the quality loss is more noticeable, especially on
closer inspection.

14. Name of compressed file format :
.rar
.zip
.pf
.7z
.arc
.tar
.iso
Etc…………..

15. 2. Continuous amplitude signals
 What is continuous signals ?
  A continuous signal or a continuous-time
signal is a varying quantity whose domain, which
is often time, is a continuum.
 X = sin (t)
 T= 0  pi

16. A typical example of an infinite duration signal is:
A finite duration counterpart of the above signal could be:
and otherwise.
The value of a finite (or infinite) duration signal may or may not be
finite. For example,
and otherwise,
is a finite duration signal but it takes an infinite value for .

17. Thank you all