3. Group members
Name ID
1. Effat Jahan 18-38718-3
2. Abu Sufiyan
3. Adittya Chakrabarti
4. Edesh
5. Monaem
4. Things to discuss about
What is compression?
Lossless compression and Lossy compression.
Difference uses of lossless and lossy compression.
Which compression method is more useful and why?
Advantages of data compression.
Disadvantages of Data compression.
6. Lossless Compression:
Lossless compression technique as their name implies, it involves
loss of information or data. In lossless compressed the original
can be recovered Exactly from the compressed data.
Lossy Compression:
Lossy compression techniques involves some loss of data or
information that have been compressed using lossy techniques
which can not be recovered or reconstructed exactly.
7. Lossy:
Non-essential data is permanently removed.
There is a degradation of data.
You can’t get back the original file.
Cheaper.
Requires less space and time.
8. Lossless:
Basic methods of compression which summarizes consecutive patterns of the
same data.
Works well with sounds and images where data is repeated.
You can get back the original data from the compressed one.
Requires more space and time.
The no degradation of data.
11. Lossless compression uses
Image file formats, like PNG (Portable Network Graphics) or GIF (Graphics
Interchange Formats), use only lossess compression.
TIFF (Tagged Image File Formats) and MNG (Multiple-image Network Graphics)
may use lossess compression too.
Lossess audio formats are mostly used for archiving or production purposes.
Lossless Compression is used in Dictionary Encoding.
e.g “Station” , “Nation” , “Creation” = 21,31,41
Data Token
tion 1
sta 2
na 3
crea 4
12. Lossy compression uses
Lossy Compression is very useful for images , audio signals, or other information that is
perceived through our senses.
Used for unnecessary data removal in video files. (In MPEG)
Removes sound in frequency range that cannot be easily heard or has the least
effect.(In MP3)
Tires to reconstruct image without missing data (In JPEG)
13. Which compression method is useful and
why?
Usefulness of a particular compression method depends on some factors.
Type of the file.
The users personal choice.
If image or sound quality matters more then lossless compression is more useful
than lossy compression.
If file size is needed to be reduced then Lossy compression is more useful then
lossless
14. Advantages of data compression
Less disk space (more data in reality)
Faster writing and reading
Faster file transfer
Byte order independent
Variable dynamic range
15. Disadvantages of data compression
Added complication
Effect of error transmission
Slower for sophisticated methods (but simpler methods can be faster for writing
disk)
In lossy compression media compression quality decreases a lot
“Unknown byte /pixel relationship
Need to decompress all previous data
