Compression - Computerphile

I had no idea computerphile was this old. Even crazier how it was just as good then as it is now. Most channels back then still felt more "public access". Then again, there were some jewels on public access TV in the 90's.

All pictures have some pattern. Only truly random data has no predictable pattern.

Thanks

the JPEG is very good...

straight to the point this is 100% clean video I've ever seen keep it up from 2020 : )

6 years later, AI can fill the pixels of a pixelated image

My lecturer asked our class to search about data compression & data encryption , and I stumbled upon this video. I was surprised to see that he's a professor at the University of Nottingham, which is also the same university that I'm attending right now.

I love the nonchalant and easy-to-understand way you explained encryption, professor! 👍🏼

years ago I saw a full windows 7 iso file in a rar archive at only ~15 Mb. I tried it on a virtual machine and it worked fine. can anyone explain how they get such massive compression?

Please can you make a video of Context Tree Weighting?

Shouldn't it be possible to store a list of the most common words locally on both the sending and the receiving computer. Then, when compressing a text file, the computer looks up each word of a text and replaces it with the index number of this word within the list (if a word is not in the list e.g. names etc. it would just skip it) and then send a massively compressed file, which is lossless (at least as long as the receiving computer has a word list on it)

Probably one of the best explanations about something technical I've ever heard. Bravo!

This is the best explanation I have ever watched regarding compression... Professor David Brailsford is awesome !!

This is to good to be free.

Hi Computerphile. I was curious when it came to sending data from point A to point B, why do we only send data in binary? For example, using fiber optics, if we divided the light spectrum into 256 colors and sent colors as information instead of on/off, every "bit" of data transfer would have a byte of information packed in it. Of course you would need high-tech senders/receivers, and perhaps that is the bottleneck, but curious to get others thoughts on this. Love this YT channel!

meaningful and relevant scenarios at this point in time going forward

The part about which pictures are simple and which aren't could have been explained a little better.
While it gets the point across, the examples aren't very good.

The picture of a sea, beach and tree is actually not that simple, since there are so many shades of blue and yellow.

A good example of predictability in a picture is e.g. a frame of a movie which has the black "letterbox" areas at the top and bottom.

I can listen to him all day!

I know this sounds crazy, but it is possible to get substantially higher compression rates than achieved today by predicting the future.  I came up with the principle and demo over 30 years ago.

i like how he uses the word "predictability" instead of patterns (all the time).
if he's a teacher i'd like to attend his classes, he's kinda tranquilizing and explains well.

Perfect for study breaks

mp3 is lossy right?

LZW and LZ77.-_-

You've gotta go tip-to-tip for optimal efficiency – use the middle-out!

pied piper does this well

I just converted this video for playback on a 1x CD-ROM drive with NO compression whatsoever.
120x90x8bit indexed color 12.5fps, 8bit 8khz mono.
I have too much time on my hands.

So, is it actually efficient to write a compression program that simply does what you said? Like, all you do is take out key character combinations or words and then seed them in the file as necessary?

I feel the need to try this myself.

I came up with the dumbest idea for my friend and I to develop, a lossy alternative to .zip and .rar. Just imagine all the affects you could get.

This was really interesting! I'd always wondered how this worked. Thanks :) 

I usually go lossless for images, but once it gets to things like music and video I tend to go for high quality lossy. As long as that JPEG is set to 85% or above in Paint.net or that mp3 has a bitrate of at least 192 kbps, I probably won't notice. It has it's huge advantages as well, as lossless compression can make videos that usually follow a ratio around 1 GB per hour. Even if you are at "100%" lossy, you still get a much more efficient file size while it is still indistinguishable from the lossless.

Is it not possible to compress the hexadecimal or binary code of the image just like a text file?

i rather download a highly compressed file and wait for it to decompress. Im my case, CPU's power is not the issue but bandwidth caps are.

This may be a different story for someone else

One thing i would like to see explored here or in another video would be compression of several files vs data deduplication of several files. Data deduplication is a completly different technique but it is also quite fascinating i think.

I really do love these compression videos

Could you come up with an iterative process of simply pattern compression to make some awesome compression system?

He sounds sooo passionate about this!!!

Great explanation. It's basically like factoring out an equation. All about efficient use of space

Couldn't you compress a photo that is saved as
"this pixel is ffffff, this pixel is 000000, this pixel is ffffff, this pixel is 000000" as
"color ffffff is in pixels 1 and 3, color 000000 is in pixels 2 and 4"? Then all you need to do is list each color used in the picture, then mark which pixels have which colors, rather than list each pixel with a color.

This guy saves me 15% or more on my car insurance...

He's talking about Run Length Encoding (RLE), which means instead of repeating a certain byte, you just have one and a number of repeats.

But to clarify, I'm more dumbfounded by the people that have chosen to mark the questioner's completely reasonable comment as spam and up-vote an answer that is inherently false. You had a guess at it and there's absolutely nothing wrong with that, but I'm more blown away by people who've forgotten the meaning of "no such thing as a stupid question". Stupid questions are the beginning of new knowledge. :3

... not that I am any authority on the British accent as I'm from almost the exact opposite side of the world. :D

The frames don't necessarily need to be similar looking - just parts of the frame. You can still get good compression if the frames are different enough, as long as there is enough redundancy between frames. Google "Temporal Motion Compensation" for more info on how it works! ( or Bing, if you're that way inclined :3 )

Ahh... no. :D Plenty of Brits say pixels like an American would say it (source: British coworkers, family and friends); it's a matter of taste, NOT accent. Pixels is a portmanteau of "Picture Element", so the L sound may be more correct (GIF's creator says it is supposed to be "Jif", but "G" is for "Graphics", same story). I don't know why the message you replied to is marked as spam and this is a top comment! estebanrey asked a perfectly valid question, and you're quite wrong ;)

Without compression this video would be 1920pixel*1080pixel*24bit depth*25fps*(7*60+38)seconds = 569825280000bit = 71.23GB big.

Pixel = Picture Element, he might just be saying it how it was originally said

Very well explained!

6:56 No, physicists will only freeze solid when hearing about entropy after boiling their brains and putting in all the work, because they will have taken all the usable energy from the universe.

Brings me back to my engineering classes where we had to compress sound (like mp3's), would have loved if he had gotten into the details on that topic... All I can remember was that you had to do a Fast Fourier Transform (FFT)... but that's all I can recall :)