0
16kviews
Explain the need of Data Compression.
1 Answer
1
330views

• Multimedia object consists of color image, photographic or video image, audio data etc. These data object needs to be stored, retrieved, transmitted and displayed. This large data objects present two problems viz, storage and transmission.

• Transfer of data in the Internet age is very time-dependent. Take for example an audio file, which is nothing but changes in the intensity of sound over a fixed period. This audio is transferred across networks in the form of sound files. If the size of the sound files is too large, the time taken to transfer the files increases. The time taken to transfer a file can be decreased using compression.

• Compression in computer terms means reducing the physical size of data such that it occupies less storage space and memory, Compressed files are, therefore, easier to transfer because there is a sizable amount of reduction in the size of data to be transferred.

• This results in a reduction in the time needed for file transfer as well as a reduction in the bandwidth utilization even for a slow network.

• Thus, the process of reducing the amount of data required to represent information is called compression.

There are two types of compression

Lossless Compression

• Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. i.e. In lossless data compression, the compressed-then-decompressed data is an exact replication of the original data.

• Lossless data compression is used in many applications. For example, the zip file format produced by the WinZip program on a PC produces exact copies of the original material that was encoded within the zip file. It is also used in the Unix tool gzip.

• Lossless compression is , used in cases where it is important that the original and the decompressed data be identical. Typical examples are executable programs, text documents and source code. Some image file formats, like PNG or GIF, use only lossless compression.

Lossless compression techniques:

• Packbits encoding (Run Length Encoding) RLE

• CCITT Group 3 1D

• CCITT Group 3 2D

• CCITT Group 4

• LZW

Lossy Compression

• Lossy data compression, which only allows an approximation of the original data to be reconstructed i.e. In lossy data compression, the decompressed data may be different from the original data. Typically, there is some distortion between the original and reproduced data.

• Lossy compression is a data encoding method which discards (loses) some of the data, in order to achieve its goal, with the result that decompressing the data yields content that is different from the original, though similar enough to be useful in some way.

• Lossy compression is most commonly used to compress multimedia data (audio, video). This method is used where absolute data accuracy is not essential. Lossy compression is the most commonly used compression type. This compression technique is used for image documents, audio, and video objects.

Lossy Compression techniques:

• Joint Photographic Experts Group (JPEG)

• Motion Picture Experts Group (MPEG)

• Adaptive Differential Pulse Code Modulation (ADPCM)

• CCITT H.261 (Px64) Video Coding Algorithm

• Intel DVI (Digital Video Interactive)

Example:

enter image description here

Please log in to add an answer.