How on earth is this so confusing, yet understandable? To me its kinda a teeter-toter of I understand this, to I have no clue....

I know right that's how I feel about all computer science. It paradoxically seems both easy and hard at the same time, which I guess is why it is so interesting.

In lossy compression what do you mean by discarding less important information? In an .JPEG or any image related file extension i could understand that those files when they're reduced they lose quality, but what about like documents?

Lossy compression involves removing less important information and so this allows compression of files like audios, pictures or videos since the lost information might be unnoticeable but for documents, lossy compression cannot be used since it can lead to missing of some characters hence making the document unreadable so for documents only lossless compression works

How can we reconstruct the original data? Why don't people just use lossless compression?

Losslessly compressed files usually contain some sort of table that allows the original file to be reconstructed. You usually won't notice the loss of quality in images and videos caused by lossy compression and lossy compression tends to give better compression ratios than lossless compression.

how do you make information smaller and compress it even though theres a lot in lossless? how can it be made smaller with the same amount of info

Lossless compression describes data in a different way that takes up less memory. For example, instead of explicitly stating the series of numbers "1, 4, 9, 16, 25, 36, 49, 64, 81, 100", we could say "x^2 for 0 < x < 11". The two descriptions are equivalent, but the second is smaller.

Main content

Course: AP®︎/College Computer Science Principles > Unit 1

Lesson 6: Lossless data compression

The need for compression

Google Classroom

Modern computers can store increasingly large numbers of files, but file size still matters. The smaller our files are, the more files we can store.

We use compression algorithms to reduce the amount of space needed to represent a file.

There are two types of compression: lossless and lossy.

Lossless compression algorithms reduce the size of files without losing any information in the file, which means that we can reconstruct the original data from the compressed file.

Lossy compression algorithms reduce the size of files by discarding the less important information in a file, which can significantly reduce file size but also affect file quality.

We'll first explore lossless compression techniques that work for text documents, simple images, and all binary data, and then explore lossy compression techniques for photos and audio.

Want to join the conversation?

Sort by:

Lorenzo4soccer
Posted 4 years ago. Direct link to Lorenzo4soccer's post “In lossy compression what...”
In lossy compression what do you mean by discarding less important information? In an .JPEG or any image related file extension i could understand that those files when they're reduced they lose quality, but what about like documents?
Button navigates to signup pageButton navigates to signup page
(6 votes)
Answer
- Steven Lwanda
  Posted 4 years ago. Direct link to Steven Lwanda's post “Lossy compression involve...”
  Lossy compression involves removing less important information and so this allows compression of files like audios, pictures or videos since the lost information might be unnoticeable but for documents, lossy compression cannot be used since it can lead to missing of some characters hence making the document unreadable so for documents only lossless compression works
  Button navigates to signup page
  (33 votes)
aben2027
Posted 3 years ago. Direct link to aben2027's post “How on earth is this so c...”
How on earth is this so confusing, yet understandable? To me its kinda a teeter-toter of I understand this, to I have no clue....
Button navigates to signup pageComment on aben2027's post “How on earth is this so c...”
(13 votes)
Answer
- Kyle Chmielowski
  Posted a year ago. Direct link to Kyle Chmielowski 's post “I know right that's how I...”
  I know right that's how I feel about all computer science. It paradoxically seems both easy and hard at the same time, which I guess is why it is so interesting.
  Button navigates to signup page
  (4 votes)
nicolascor2079
Posted 2 years ago. Direct link to nicolascor2079's post “what is your favorite can...”
what is your favorite candy?
Button navigates to signup pageComment on nicolascor2079's post “what is your favorite can...”
(8 votes)
Answer
- Mason H
  Posted 9 months ago. Direct link to Mason H's post “Reeses cups”
  Reeses cups
  Comment on Mason H's post “Reeses cups”
  (2 votes)
chansovanmonyyoeun03
Posted 3 years ago. Direct link to chansovanmonyyoeun03's post “How can we reconstruct th...”
How can we reconstruct the original data? Why don't people just use lossless compression?
Button navigates to signup pageButton navigates to signup page
(3 votes)
Answer
- KLaudano
  Posted 3 years ago. Direct link to KLaudano's post “Losslessly compressed fil...”
  Losslessly compressed files usually contain some sort of table that allows the original file to be reconstructed.
  
  You usually won't notice the loss of quality in images and videos caused by lossy compression and lossy compression tends to give better compression ratios than lossless compression.
  Comment on KLaudano's post “Losslessly compressed fil...”
  (8 votes)
21jmclean
Posted 8 months ago. Direct link to 21jmclean's post “This is very interesting ...”
This is very interesting 🤔🤔💭
Button navigates to signup pageComment on 21jmclean's post “This is very interesting ...”
(6 votes)
Answer
Ashwika Ganti
Posted 2 years ago. Direct link to Ashwika Ganti's post “how do you make informati...”
how do you make information smaller and compress it even though theres a lot in lossless? how can it be made smaller with the same amount of info
Button navigates to signup pageComment on Ashwika Ganti's post “how do you make informati...”
(2 votes)
Answer
- KLaudano
  Posted 2 years ago. Direct link to KLaudano's post “Lossless compression desc...”
  Lossless compression describes data in a different way that takes up less memory. For example, instead of explicitly stating the series of numbers "1, 4, 9, 16, 25, 36, 49, 64, 81, 100", we could say "x^2 for 0 < x < 11". The two descriptions are equivalent, but the second is smaller.
  Button navigates to signup page
  (6 votes)
hinesj10690
Posted a year ago. Direct link to hinesj10690's post “Lossy compression involve...”
Lossy compression involves removing less important information and so this allows compression of files like audios, pictures or videos since the lost information might be unnoticeable but for documents, lossy compression cannot be used since it can lead to missing of some characters hence making the document unreadable so for documents only lossless compression works
Button navigates to signup pageButton navigates to signup page
(3 votes)
Answer
wyatt.johnson3561
Posted 7 months ago. Direct link to wyatt.johnson3561's post “So what is a good example...”
So what is a good example of lossy data?
Button navigates to signup pageComment on wyatt.johnson3561's post “So what is a good example...”
(3 votes)
Answer
- aidencosgriffkalter
  Posted 7 months ago. Direct link to aidencosgriffkalter's post “changing the size of an i...”
  changing the size of an image to be smaller then the original, you can notice the quality of it goes down when you resize an image to be smaller then the original size
  Button navigates to signup page
  (1 vote)
leonardo.wiest
Posted 7 months ago. Direct link to leonardo.wiest's post “Zǎo shang hǎo zhōng guó! ...”
Zǎo shang hǎo zhōng guó!
Xiàn zài wǒ yǒu bing chilling
Wǒ hěn xǐ huān bing chilling
Dàn shì "sù dù yǔ jī qíng jiǔ" bǐ bing chilling
"sù dù yǔ jī qíng, sù dù yǔ jī qíng jiǔ"
Wǒ zuì xǐ huān
Suǒ yǐ xiàn zài shì yīn yuè shí jiān
Zhǔn bèi
Yī, èr, sān
Liǎng gè lǐ bài yǐ hòu
"Sù dù yǔ jī qíng jiǔ"
Liǎng gè lǐ bài yǐ hòu
"Sù dù yǔ jī qíng jiǔ"
Liǎng gè lǐ bài yǐ hòu
"Sù dù yǔ jī qíng jiǔ
Bù yào wàng jì, bù yào cuò guò
Jì dé qù diàn yǐng yuàn kàn "sù dù yǔ jī qíng jiǔ"
Yīn wéi fēi cháng hǎo diàn yǐng
Dòng zuò fēi cháng hǎo
Chà bù duō yī yàng bing chilling
Zài jiàn
Button navigates to signup pageComment on leonardo.wiest's post “Zǎo shang hǎo zhōng guó! ...”
(3 votes)
Answer
jeff li
Posted a year ago. Direct link to jeff li's post “do we have any videos for...”
do we have any videos for this? Reading on computer hinders my comprehending quality lol
Button navigates to signup pageComment on jeff li's post “do we have any videos for...”
(3 votes)
Answer