Compression method

NotAGolf · 9 Apr 2010 at 18:41

I'm looking to backup a load of my videos, music and pictures. I've got hold of an old hard drive I can bung them onto but it's only 320GB which isn't big enough for everything so I was thinking of compressing the files so I can squeeze a few extra on (I'm talking about a compressed archive format rather than compressing individual files). 2 questions before I do this:

- Is it worth it? Obviously 320GB of data will take a while to package up so I don't really want to waste several hours for the sake of 5GB. (95% of the files are .avi, .mp3 or .jpg if that makes a difference)

- If so, what is the best format is likely to yield the most compression? RAR, ZIP, TGZ, TAR, 7z etc

Thanks for any help.

Tomsk · 9 Apr 2010 at 18:54

Not worth it.
avi, mp3 and jpg are already compressed.

Pho · 9 Apr 2010 at 18:54

Videos, music and pictures don't compress very well as they're probably already compressed. Your best bet would be to find a bigger drive (lots go on the MM here) I imagine.

mrk · 9 Apr 2010 at 19:12

Tomsk said:
Not worth it.
avi, mp3 and jpg are already compressed.

AVI is a container, it is not compressed neither a format.

Tomsk · 9 Apr 2010 at 19:20

Khaaan! said:
AVI is a container, it is not compressed neither a format.

OK, but it usually contains compressed video and audio data.

mrk · 9 Apr 2010 at 19:25

It also usually contains uncompressed video and PCM audio!

HangTime · 9 Apr 2010 at 20:04

To answer the OP as mentioned you won't gain much as most of your media files will already be compressed. However if you really do need to squeeze up to say 5% extra have a look at 7zip max (for ease of use) or if you have a LOT of time on your hands, something like PAQ8px or similar variant (an extremely hardcore compression program, commandline only, would likely take days to compress 320GB).

Basically it's one of those situations where you have to ask yourself, is it really worth the hassle of compressing, as then you'll have to decompress when you want to actually open that media in the future? PAQ8px will blow the likes of zip/rar/7z out of the water when it comes to compression filesize but since the idea of waiting hours (nevermind days) scares you it's one of those situations where you'll end up regretting not simply getting a bigger drive. I recently got a 1TB USB2 drive for £55 brand new.

NotAGolf · 9 Apr 2010 at 22:29

Thanks for all the advice guys.

How much compression do you think I could achieve with PAQ8px HangTime? Much more than 5%? I don't have a problem with leaving it compressing for days if I get decent compression.

Hopefully I wont ever have to go back to it as it's just a backup, and I've already got my music/photos backed up on dvd's, but I thought if I've got some spare kit laying around I might as well make use of it. I cant justify the cost of another hard drive as I just bought a 1TB and the majority of stuff is already backed up.

HangTime · 10 Apr 2010 at 10:11

To be honest I don't know. According to www.maximumcompression.com they got 24% on a jpg file, but YMMV. I experimented a bit with an earlier version (PAQ8o) a while back and it seemed effective (especially for Word documents with embedded images) but I've not tried video files.

My recommendation would be to give it a test on smaller files (say a 20meg .avi) and see what the result is. Chances are it's the .avi files taking up the most space so unless you are getting a good compression ration on them it's not going to be worth it.