Right. mp3 is already a compressed format which means most of the
duplicate information has already been extracted out of the file. There
won't be much, if anything, a generalized compressor can do. Only way to
make mp3s smaller is to re-encode them with lower quality (a lossy
compression).
I ran another test using zip -9 on my keynote app and it produced a
453,726,061 byte (453.7MB) file which is pretty much the same result as
I got when choosing Compress from the file menu. So maybe Apple defaults
to -9. With today's CPUs the compressions process is more likely IO
bound rather than CPU bound, at least with spinning disks.
CB
On 3/26/15 2:29 PM, Todor Fassl wrote:
Yeah, a folder full of mp3 files isn't going to compress much. The xls
files will compress a lot but they probably take up very little space.
Different compression algorithms work better on different kinds of
data. What a tool can do is look at each file and dtermine which
algorithm to use to compress it. 7-zip might do a better job of that
than regular zip. But probably to really do a valid test you'd have
to tell zip to do it's best compression with the -9 command line option.
I predict that neither will do much with a folder full of mp3 files
though.
On 03/26/2015 11:04 AM, Joe Quinn wrote:
Rats cause what I wanna compress is MP3 and off/XLS files in the same
folder
Sent from my iPhone
On Mar 26, 2015, at 10:26 AM, 'Chris Blouch' via MacVisionaries
<macvisionaries@googlegroups.com> wrote:
I compressed my copy of Keynote, which is really made up of
thousands of files under the hood totaling 611,951,069 bytes (692.5
MB). To test unix compress I did
tar -zcvf test.gz /Applications/Keynote.app/
which generated a compressed file of 428,440,218 bytes (428.4MB) or
about 61.9% of the original file size. Doing the same thing through
the finder I selected Keynote and then chose Compress from the File
menu. That generated a zip file of 453,379,578 butes (453.4 MB) or
65.5%. Just for the fun of it I also tried doing a 7-Zip. Downloaded
a 7-Zip app for OSX from here:
http://www.updatestar.com/directdownload/7zx/2188433
which generated a .7z file of 375,098,819 bytes (375.1MB) or about
54%. So it looks like 7-zip is the smallest (11% smaller than plain
zip in my test) but the downside is that it's not very popular. If
you send this to someone else they will have to go through the
bother of finding, downloading and installing an app to uncompressed
it. Pretty much everyone can handle a zip file without much trouble.
As with all compression, the results are also based on what you are
compressing. Text, which has lots of repeating patterns, compresses
really well. Binary files such as audio, video and images might not
compress at all.
CB
On 3/25/15 7:38 PM, Joe Quinn wrote:
now that SArchiver’s gone down the tubes? what’s the best archiving
utility for the mac? i wanna be able to compress files as small as
humanly possible, but still retain quality. thanks for any info!
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