| From Toth
| Thu, 30 Aug 2007 21:32:21 -0700
| Subject: [Audacity-help] mp3 question
| if i load an mp3 file into audacity (or any other wave editor)
| and edit say the ID3 tags, and then export as mp3 again, will this
| reduce the quality of the mp3 file?
| simply put: exporting an mp3 over an existing mp3 file, will this
| keep the quality of the original file?
| (like if you save a jpg over a jpg, i believe it will reduce the quality
| of the image)
Yes, whether saving an image, video file or audio file, the problem is the
same: re-encoding it in a compressed format will reduce its quality. If the
file you are encoding is already lossily compressed as an MP3 is, re-encoding
it to a lossy format will therefore result in two steps of degradation: the one
that created the file in the first place, then the re-encoding in the editor.
Re-encoding the MP3 when you export it cannot be avoided in Audacity,
because Audacity always decompresses the MP3 upon import. This is
essential to maintain the quality of the file when applying complex edits
such as equalisation.
But if you only want to do simple cut, copy, paste, fade and volume edits to
your MP3s, you can do so without audio losses in other tools that can edit the
MP3s directly without decompressing them, and thus without the need to
to re-encode them. Two examples are MP3DirectCut for Windows and Linux
(under Wine):
http://www.mpesch3.de/and Audion (OS X)
http://www.panic.com/audion/
MP3s of the same bitrate, sample rate and number of channels can also be
joined losslessly with these tools.
Or here is a similar audio cutter for Windows that can losslessly cut and join
OGG as well as MP3 (OGG is a lossy compressed format of slightly higher
quality than MP3 which is also supported by Audacity):
http://musicutter.szm.sk/
A possible alternative is to encode after editing to a lossless compressed
format such as WMA Lossless (supported by Windows Media Player),
Apple Lossless (supported by iTunes) or FLAC. Of these, Audacity 1.3.3
(our latest Beta unstable version) can import and export FLAC. Lossless
compressed formats typically achieve a 1:3 or 1:4 compression, compared
to 1:10 for a 128 kbps MP3. On the other hand lossless compressed formats
are not so portable as MP3, so if you are distributing your files to others,
MP3 remains the format you should use because virtually any computer will
be able to play them.
Gale Andrews
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