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Windows 7: Confused with various compression levels

20 Jun 2015   #1

Windows 7 x32
Confused with various compression levels

There are different levels of compression available in 7zip. I am kinda new to it and don't know the difference. Can someone plz help ?

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Confused with various compression levels-7zip.jpg  
My System SpecsSystem Spec
20 Jun 2015   #2

Windows 7 Pro 32

Click the help button :)

Or you can try different levels and compress copies of one single file, to see the difference both in size and how long it takes. Don't use a small file though or the result won't tell you much.

I almost always use the default options. And the .7z format is better than .zip
My System SpecsSystem Spec
20 Jun 2015   #3

Windows 7 x32

Thanks, Tookeri. Ur idea is good. But I have files of size not more than 1.5GB - basically movies. Will it show some effect there ?
My System SpecsSystem Spec

20 Jun 2015   #4

Windows 7 Ultimate x64

In any compression utility, the compression level tune how aggresively will the program attempt to process the input data. Higher levels will try to search for more redundancy, more advanced techniques and analyze the files more carefully in an attempt to further reduce the final size, but tend to increase the time needed to process the whole thing.

In short, that option lets you specify a trade-off. Higher compression level or shorter compression time? The "none" option doesn't compress at all, but it's very fast, while the best option will get the smaller file, but taking a long time. It's up to you what to prioritize. I always chose the best option for getting the smaller file.

About your last comment ("basically movies"), it's not a good idea to try to compress any multimedia file, with any program or compression level. Movies, and also images and audio, are internally already compressed (with special-purpose algorithms) that make 7zip-like programs useless. Almost always you'll get a "compresed" file as big as the original, no matter what options you choose.
My System SpecsSystem Spec
22 Jun 2015   #5

Windows 10 x64

Alejandro is right. Movie files (and audio files) are already compressed (in most cases). Running them through additional compression is pointless. It might be instructive to look at why this is so ...

Compression algorithms work by finding redundancy in the data and removing it. Subsequent un-compression works by restoring that redundancy.

So when a video is compressed (and the data redundancy is removed), further compression is not possible. There's simply no more redundancy to remove.
My System SpecsSystem Spec

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