How to compress 5GB file into 50mb or less ?

[SANTACLOWN]

How can we compress a large file

such as iso or mp4
into a small size 50mb or less ?

[Q91]

That's NEAAAAAAAAAAAAAAAAAR impossible, unless you want to encode at 320x240 at a bitrate less than 400kbps. You will have HUGE quality loss. You'd be happy if you can get a DVD movie under 600MB without any huge losses

[nosnavis]

When you compress something (losslessly, like .rar files), you try to find all pattern-following data in your file, and then make algorithms to recover the original data. What you cannot compress is the "noise" in the file, the data that is chaotic. That's a hard fundamental limit called the Shannon limit. If the file has too much chaos, it just can't be compressed. If the file has much redundant info, it can be done, but the original file should be something "boring" like a bunch of zeroes in a row, a one note audio file, etc.

Lossy compression makes approximations that remove information from your data set, so the quality does go down. Mp3's use this, they remove parts that our brain has difficulty discerning anyway, so they can afford to lose lots of info before you can sense a real quality loss. But after a limit, the quality makes the resulting file unusable, depending on what you want to do with it. Like, where the text is the important part, like audiobooks, you can use 32kbps mp3 compression, but you can't do that for music.

You can reduce the data itself, like using smaller video frame sizes, reducing the frames per second, etc. There are ways, but it's not a straightforward way for everything, and it depends on the original data and the quality you want at the end.