Compression

What is Compression and why is it used

• Compression is reducing the the size of a file so that it takes up less space on secondary storage

• Compression can be achieved using two methods, lossy and lossless

• Minimise the transfer time of data being uploaded, downloaded or streamed across a network as they take up less bandwidth such as the Internet

• -Allows web pages to load more quickly in web browsers

• Compressing file allows you to send same content with a much smaller file size

What is lossy compression and when is it used

• Lossy compression is when data is lost in order to reduce the size on secondary storage(limits the number of bits the file needs and so reduces its size)

• Lossy compression is irreversible

• Lossy can greatly reduce the size of a file but at the expense of losing quality

• Lossy is only suitable for data where reducing quality is acceptable, for example images(.jpg), video and sound(.mp3)

What is lossless compression

• Lossless compression is when data is temporarily removed to reduce the size on secondary storage

• Lossless compression is reversible, the file can be returned to its original state

• Lossless can reduce the size of a file but not as dramatically as lossy

• Lossless can be used on all data but is more suitable for data where a loss in quality is unacceptable, for example documents,sound(.flac),images(.gif),files(.zip)

Compare lossy and lossless in terms of text files,databases and programs

Certain files like text files, databases and program code cannot be compressed using lossy compression as losing any characters would render them unusable. Although lossless compression keeps the original file in tact, the trade-off is that it does not compress the filesize as much as lossy compression.

What are the Pros and Cons of Lossy compression

Advantages:

Greatly reduced file size meaning more files stored

-Lossy files take up less bandwidth so can be downloaded and streamed quickly

-Commonly used as lots of software can read it

Disadvantages:

-Lossy compression loses data-file can’t turn back to original

-Lossy compression can’t be used on text or software files as these files need to retain all the information of original

-Lossy compression are worse quality than the original. But it’s unnoticeable

What file types are used for lossy compression

-MP3(audio)

-AAC(audio)

-JPEG(images)

What are the Pros and Cons of lossless compresion

Pros:

-Dat is only removed temporarily so there is no reduced quality-the compressed file should look or sound like original

-Lossless files can be decompressed-turned back to original

-Lossless compression can be used on text and software files

Cons:

-Only a slight reduction in file size so Willy are up quite a bit of space on device

File types for lossless compression

-FLAC(audio)

-ZIP(files and folders)

-PNG(image)