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I tried my best to compress some videos, about 1.4GB each. I tried to compress them separately, "tarring" (using tar) them and then compress, everything.

I'm on OS X Lion and I did try the Compression Utility. The point is: the file sizes don't change. I also tried to use 7z but the result file was bigger than the original!

Is there some limitation about file sizes that can be compressed? Files are in .mkv format.

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The thing is that video files are already compressed, so it's like ziping a zip file. – week Dec 5 '12 at 9:12
@week - might as well post that as an answer. – Henk Dec 5 '12 at 9:13
up vote 3 down vote accepted

Files are in .mkv format.

Sadly this gives us no clue as to what format the files are actually in. Both .mkv and .avi are container formats.

However most video files are distributed in an already compressed format. (Otherwise you could only stores a few seconds of high resolution movies even in 1GB files).

Trying to compress already compressed files usually does not work well. Especially if those files are already compressed with prior knowledge of their contents and you are trying to use a generic lossles compression algorithm.

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Thank you. This is unfortunate but anyway thanks! – mmassaro Dec 5 '12 at 12:50

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