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'): 20256 track01.flac 4592 track01.mp3 3792 track01.ogg 37584 track01.wav 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': 20240 track01.flac.gz 4560 track01.mp3.gz 3760 track01.ogg.gz 33840 track01.wav.gz 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': 20336 track01.flac.bz2 4560 track01.mp3.bz2 3776 track01.ogg.bz2 32080 track01.wav.bz2 Next up is 'rzip -9': 20240 track01.flac.rz 4560 track01.mp3.rz 3776 track01.ogg.rz 32080 track01.wav.rz And finally 7zip '7z a -mx=9': 20448 track01.flac.7z 4576 track01.mp3.7z 3760 track01.ogg.7z 31424 track01.wav.7z 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. Roland -- R.F.Smith http://www.xs4all.nl/~rsmith/ [plain text _non-HTML_ PGP/GnuPG encrypted/signed email much appreciated] pgp: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 (KeyID: C321A725)
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