Compressed Files Larger?

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Phexx

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#104712 20-Jun-2012 18:15

Hi, I am trying to compress fles to put into a backup. I am using 7-Zip to compress the files. My settings are all default except compression level which is maximum. When I compress the files I they are about 4.2GB before, then 4.4GB after? Am I doing anything wrong, ideally I would like to get the files as small as possible.

freitasm

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#643952 20-Jun-2012 18:25

This can happen. What kind of files are these? Text, images, programs, music, video?

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Phexx

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#643955 20-Jun-2012 18:38

Videos, I can't seem to get them any smaller.

freitasm

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#643961 20-Jun-2012 18:51

You won't get videos any smaller, and sometimes bigger. Compression only works well in certain files.

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Jarno

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#643963 20-Jun-2012 18:53

The videos are already compressed. If it were (easily) possible to losslessly compress the videos significantly further, then that step would be part of the video compression standard.

hellonearthisman

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#644018 20-Jun-2012 20:45

It's strange that the compression software doesn't notice the result it larger than the original and just store the original file uncompressed. There can't be 200MB of extra data added in compression headers.

As for Jarno's point, yes, they are compressed for streaming but no streaming compression should have a better result. I guess that the compressor would need to read the compressed video format and then perform another layer of compression on the complete file.

One of the limits with complex compression like that is processing speed and memory/file access.
Most compresses like 7zip rar... are concerned about compression speed. Not many people would wait 24+ hours to compress a few files.

gzt

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#644055 20-Jun-2012 22:33

What were the videos created with?

The best strategy for reducing the size may be transcoding them to divx or some other very high quality small footprint format and keeping the same quality.