best archiver? (for music)
rsmith at xs4all.nl
Fri Mar 13 13:22:30 PDT 2009
On Fri, Mar 13, 2009 at 12:15:24PM -0700, Gary Kline wrote:
> guys, this is for any compression experts on-list. my main
> desktop is nearly full. i'm looking for the best means of
> compressing [mostly] audio files. mp3, ogg, and .flag.
All of these are already compressed. Trying to compress them further is
a waste of time. See below. You can make smaller mp3 or ogg vorbis files
by encoding them at a lower bitrate or quality setting.
I did a test on compression some time ago.
I started with a track ripped from CD by cdrecord. I used 'lame -V 2' to
convert to mp3, 'oggenc -q 5' to convert to ogg vorbis, and 'flac -6' to
convert to flac.
File sizes were (in kilobytes, using 'du -k'):
The mp3 and ogg files are small because they employ 'lossy'
compression. On the other hand, flac is lossless compression. I tried
several (obviously lossless) archivers.
First I compressed them all with 'gzip -9':
As you can see these sound files don't compress well. The first three
because they are already compressed, and the wav file probably because
the gzip algorightm isn't a good match for sound data.
Then I tried with 'bzip2 -9':
Next up is 'rzip -9':
And finally 7zip '7z a -mx=9':
My conclusions were:
- The general archivers can compress the wav somewhat without loss, but
none do as well as the dedicated lossless compression program flac.
- Trying to compress mp3, ogg and flac files further is a waste of time.
- If you want smaller files, use lossy compression like mp3 or ogg
vorbis, and pick the lowest quality level that sounds acceptable to you.
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