Compress MP3 downloaded from the web?

Question

I recently downloaded a bunch of raw audio streams from the web as MP3s and I realize now that they're huge! 60 MB a song… I would like to compress these, but the other question similar to mine links to a software for Windows, and I have a Mac.

The streams are an hour, so I guess that might be one reason they're so large.

First, I wasn't looking for a program to buy or download to do this, but rather wanting to know if I could use Flash, GarageBand, AfterEffects or any other program to import the stream, lower the quality a bit, and export it.

Secondly, there would be no video inside because it's not coming from a video.

Solution 1

iTunes allows you to easily compress these files. Just drag them to your music library, then open Preferences » Import Settings….

Select the MP3 encoder and then click Setting » Custom…:

Select a custom bitrate here. Now, your one-hour files with 60 MB seem to have a reasonable size anyway – you'd expect 1 MB per minute of music for MP3s. However, if you want to re-encode them to become smaller, select something less than 128 kBit/s here. Note that this will reduce your quality, and it might lead to enormous quality loss. Recompressing something that's already compressed generally isn't a good idea.

Once you've set all that, go to your file in the library, right click and select Create MP3 version.

You can now right-click the new version and select Show in Finder to reveal the newly created file.

Solution 2

Since you don't want to download anything, I hope you have LAME installed already. Here's how you can decode and encode your MP3 file a lot easier than with iTunes.

lame --decode soundfile1.mp3 soundfile1.wav
rm soundfile1.mp3
lame soundfile1.wav

Example session:

% ls -l 01.\ Drive\ My\ Car.mp3 
-rwxrwxr-x 1 janus plugdev 6064941 jan 26  2012 01. Drive My Car.mp3
% lame --decode 01.\ Drive\ My\ Car.mp3 
input:  01. Drive My Car.mp3  (44.1 kHz, 2 channels, MPEG-1 Layer III)
output: 01. Drive My Car.wav  (16 bit, Microsoft WAVE)
skipping initial 1105 samples (encoder+decoder delay)
skipping final 743 samples (encoder padding-decoder delay)
Frame#  5754/5754   168 kbps   MS
% rm 01.\ Drive\ My\ Car.mp3 
% lame 01.\ Drive\ My\ Car.wav 
LAME 3.99.3 32bits (http://lame.sf.net)
CPU features: MMX (ASM used), SSE (ASM used), SSE2
Using polyphase lowpass filter, transition band: 16538 Hz - 17071 Hz
Encoding 01. Drive My Car.wav to 01. Drive My Car.mp3
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III (11x) 128 kbps qval=3
    Frame          |  CPU time/estim | REAL time/estim | play/CPU |    ETA 
  5754/5754  (100%)|    0:09/    0:09|    0:09/    0:09|   16.338x|    0:00 
-------------------------------------------------------------------------------------------------------------------------------------------
   kbps        LR    MS  %     long switch short %
  128.0       89.6  10.4        91.6   4.7   3.7
Writing LAME Tag...done
ReplayGain: -3.7dB
% ls -l 01.\ Drive\ My\ Car.mp3 
-rw-rw-r-- 1 janus plugdev 2405354 okt 21 19:28 01. Drive My Car.mp3

As you can see, the default settings gives you a file with less than half the size of the original, using the original file.

If you don't have LAME, but you do have internet: get homebrew and then brew install lame && brew link lame

Comments

[ganesh]

1) If you already saved them as MP3 then they already are extremely compressed. 2) This feels as a shopping question for a best program to do this.

[cloneman]

MP3s are not that big. You probably downloaded the video too,embedded inside, or the file is corrupt. MP3 128kbps files are about 5 Megabytes for a 5 minute song. if I knew of a program to split audio and video besides the outdated VirtualDub, I'd suggest that.

[slhck]

LAME doesn't come by default on OS X, so it would be great to explain how to get the binary in the first place.

[Janus Troelsen]

@slhck: added :)

[slhck]

Nice, thanks! Note that brew does not accept sudo anymore, at least since a couple of months. IIRC the linking step is not necessary, but I might be wrong.