MP3 on a Macintosh
Disclaimer: any opinions expressed in this article are those of its
author ( comartin@wicc.weizmann.ac.il
) and do not purport to represent Weizmann Institute of Science policy.
What the PC is MP3?
The short answer: MP3 stands for MPEG (Motion Picture Experts Group) Layer
3. It is an audio compression format that on average yields near-CD quality
at one-tenth the size. That is: a regular CD, which holds about 74 minutes
of uncompressed music, can hold something like 12-13 hours worth of MP3
files.
MP3 is a so-called "lossy compression" algorithm, which (like JPEG
for pictures) takes advantage of the limitations of human perception to
achieve very high compression ratios (10:1 is common for sound). This stands
in contrast to so-called "lossless" algorithms, ike GIF for pictures, as
well as such popular file compression formats as ZIP on PCs, gzip on Unix
systems, and StuffIt on Macintoshes. Lossless algorithms merely exploit
repetition, redundancy,... in the original file to arrive at a compressed
representation, but do preserve all the details of the original. The upshot
is that they generally achieve much lower compression ratios (2:1 or 4:1)
than lossy algorithms.
For the long answer, check out the MP3
Technical Info and FAQ
at the Fraunhofer-Gesellschaft.
Is MP3 encoding legal?
No more or less than taping. That is, encoding one's own CDs for personal
use is perfectly legal, but selling MP3 files encoded from commercial CDs,
without paying royalties, isn't.
Are there any good encoders for the Mac?
A detailed review can be found here
. The two best general-purpose encoders for Macintosh appear to be, ex-aequo,
Proteron
N2MP3 and Xing AudioCatalyst
. Both programs are commercial: AudioCatalyst can be downloaded upon online
payment, while
N2MP3 comes as an evaluation version that
will let you encode 20 tracks per installation, and preface every track
with a spoken "Encoded by N2MP3" message. (Upon online payment of the registration fee, one receives a password to remove these limitations.) Macromedia
SWA Export Xtra (based on licensed Fraunhofer code) does a great job
as well, but is quite slow even on G3 machines. It is a freeware plug-in
for the expensive Macromedia Director multimedia software, but Johan Lindvall
developed a freeware hack
that allows one to use the plug-in without Director.
Casady & Greene SoundJam
MP is a popular commercial encoder/player combination, with lots of
fancy bells and whistles like graphic equalizer, spectrum analysis while
playing, etc. Unfortunately, when it comes to the music itself, it does
a comparatively poor job, as witnessed both by the above review and yours
sincerely. Stop Press Jan 17, 2000: recent versions of SoundJam's
encoder (1.5 and above) are reported to be dramatically improved in quality,
although I have been unable to verify this myself.
Recently, a Macintosh port of the GNUware
Blade Encoder has been brought out.
Based on ISO reference encoder. User interface as primitive as it gets,
but can't complain about the price. Author claims that quality should
surpass that of Fraunhofer engine at 160kbps and higher, since the
Fraunhofer algorithms are optimized for 128 kbps and lower.
A detailed review
found it to be distinctly inferior to N2MP3 and AudioCatalyst, as well as
to never versions of SoundJam run at high bitrates (160 kbps and above).
A newer public domain encoder called LAME (Lame Ain't an MP3 Encoder)
appears to be a better bet if you want freeware: I will post a link for
a Macintosh binary as soon as I can get hold of one.
Stop Press March 6, 2000: you can download one called
CocaCoda, albeit with a Japanese language interface: an
English Language Patch
is available.
Neither LAME nor Blade can encode directly off CDs, but you can copy them
as AIFF files first using
Track Thief...
What about MP3 players for Macintosh?
There are two considerations: playback quality and processing overhead.
Last but not least, there's cost.
-
QuickTime 4 (from Apple itself)
has an MP3 playback engine licensed from Fraunhofer. Quicktime 4 can be
downloaded for free (in fact, I'd recommend doing this whether or not you
use MP3, since it has plenty of other features that were not present in
QuickTime 3) and yields excellent playback quality. It has one major disadvantage:
an annoying tendency to pause, skip, or produce extraneous noises whenever
system operations take place (opening and saving files, starting programs,
...) — even opening new windows. Also, it does not support VBR files, and
I've had trouble making it open even fixed bitrate files at 160 kbps.
-
Quicktime itself does not have playlists etc., but there are a number of
freeware and shareware "MP3 players" that in fact merely serve as front-ends
for the Quicktime 4 engine, such as MP3
Voodoo (nudnikware), MVP
(free public beta), SoundSpinner
(shareware), ... that offer these kinds of features.
-
GrayAmp
is a freeware, no-nonsense player that is distinguished by its very low
drain on resources. It will be listenable on an old PowerMac, and on a
G3 Mac (including iMacs, by the way), you can have it play in the background
and still be able to do complex, CPU-intensive things in the foreground.
(It's my default player for that reason.) It does start skipping after
several hours of MP3 playing: just quit it and launch it again.
STOP PRESS Nov. 4, 1999: this problem and a number of other bugs appear
to have been fixed in version 1.1.
-
SoundApp by Norman
Franke is an excellent all-purpose sound file conversion utility as well
as a good freeware MP3 player. It is the only freeware player that is
supposed to support VBR encoded tracks, although I haven't tested this.
-
Commercial players like MacAST (formerly
MacAMP), SoundJam (see encoders),
and Audion . Usually these
contain all sorts of bells and whistles like visual plugins, "skins" (changeable
face plates), ... which are probably attractive to the more geekish among
us but have little to do with music. Also they often have equalization
in software, which is impressive and can be useful but does place a tremendous
drain on processing resources. It's the first thing I turn off.
- One exception to the rule, that I am quite taken with, is
Macast Lite 2.0. It costs
only $15 (you can run it for two weeks before having to register), does not
put a terrible drain on your CPU, has an unobtrusive interface, great sound
quality, and appears to be quite a bit more stable on my Powerbook G3
than GreyAmp (which used to be my all-round player). And like the other
commercial players, it can handle VBR encoded files.
If you decide you
want to upgrade to MacAst [full] 1.0 (same site), you get a $5 discount
off the price with your registration code for MacAst Lite.
One useful tip if you do decide to get MacAST full version: in the
Preferences, go to the "buffer memory size" and crank this up as high
as possible (1024 K is the maximum, I think) to reduce skipping during
heavy disk activity.
But how does it sound? Can you hear the difference?
I am a listener of very wide-ranging musical tastes (as long as the music
is "nonobvious") and did extensive informal testing with both N2MP3 and
SoundJam, using various kinds of music. (Since I like to have music going
while working, and the CD player on my Powerbook G3 skips whenever I
type with my usual force --- having learned
typing on a mechanical typewriter --- MP3 is my default audio entertainment.)
-
J.S. Bach, Goldberg variations BWV988, Glenn Gould, piano
(1982 digital recording). Excellent test for cleanliness and nuance in
solo instrument recordings, and in my opinion musically unsurpassed.
-
Donald Fagen, The nightfly (jazz-pop, 1982 digital recording). Very
clean recording with immaculate production technique (a favorite of audiophiles
the world over). That and the above one are my usual two test CDs when
I go to a store to check out audio equipment. Listen to it a few times
on CD, then try the MP3s.
-
Tangerine Dream, Logos part 1 (electronic, 1982). The opening sequence
contains a series of complex electronic effects that break just about every
encoder.
-
Genesis, Nursery Cryme (progressive rock, 1971, digitally remastered
1997) and/or The lamb lies down on Broadway (1974).
-
U.K., U.K. (jazzy progressive rock, 1978). Lots of textural variety,
from crisp acoustic guitars to complex synthesizer tones, plus expressive
soloing on electric guitar, keyboards, and electric violin. A tough test
for audio equipment: check for clarity in the treble.
-
Suzanne Vega, Solitude standing (female singer-songwriter). This
type of female vocal is pretty hard on encoders, particularly in passages
where the accompaniment is fairly "busy".
-
Led Zeppelin, Remasters. Classic hard rock. The openings of "Immigrant
song" and "Achilles' last stand" (after the bass comes in)
are especially hard on encoders because
of the combination of deep growling bass and heavy treble --- usually one
or the other gets distorted.
-
Metallica, "Ain't my bitch" and "Fuel" (speed metal; opening tracks of
Load
and
Reload, respectively: both digitally recorded). Even more severe
tests of the low end: the combination of high-speed guitar riffs, a 5-string
bass near the bottom end of the auditory spectrum, and drum playing that
is both agressive and very precise usually results in one or the other
thing getting messed up (usually either unpleasantly distorted bass and
mushy bass drum or
fluttering cymbals). Alternatively, any fast track on the "Black Album"
or on the 1st disc of "Garage, Inc." will do. The older (and best) work
of that band just wasn't recorded with the same level of technology and
therefore is too lenient a test.
-
Dimitri Shostakovitch, 7th Symphony "Leningrad" (1942 American premiere,
conducted by Arturo Toscanini). A low-fi mono classical recording: good
test for mono encoding at veryhigh compression (20:1). Old jazz
recordings on the Blue Note label (Charlie Parker, Bud Powell, Monk,...)
are good tests for that as well.
Why no classic Beatles, Rolling Stones, etc? Quite simply: because these
records will sound good with just about any halfway decent encoder, since
they were produced and mixed to fit the limitations of equipment with specifications
that sound laughable by today's standards.
The performance at 128kbps of SoundJam on some of these tracks (particularly the
Metallica) was pathetic. N2MP3 produced decent encodings of just
about all of them at 128 kbps, stereo, "high" quality setting. The Tangerine
Dream had to be redone at 160 kbps. I could get acceptable quality for
the Shostakovitch at 64 kbps mono (note that for mono recordings, this
is equivalent in quality to 128 kbps stereo!).
One important factor are also the quality of your audio speakers and/or
headphones. If you hooked your computer up to a quality hifi chain with
ditto speakers, it might be worth the extra disk space to encode at 160
kbps or even 196 kbps, or to go for VBR encoding (see below). If you are
using typical "multimedia" speakers, this is generally a waste of disk
space.
What do the settings for encoding mean?
I will take the example of N2MP3, my favorite encoder — but all good encoders
will have most of these settings.
-
bitrate. The only three settings I ever use are 128 kbps for general purpose,
160 kbps if that one breaks, and 64 kbps for mono recordings. These translate
into 960 KB/min, 1.2 MB/min, and 0.48 KB/min., respectively.[For reference,
an audio CD, which is sampled at 44.1 kHz at 16 bit (dynamic range of 96
dB), uses about 10.5 MB for a minute of music.]
-
quality: "normal" or "high". Use "high" whenever you can. The "normal"
setting uses a faster algorithm that however does not yield maximum sound
quality: on my Powerbook G3, a 128 kbps "normal" encoding goes several
times faster than real time, while the "high" setting can just encode
in real time if you're not doing anything else on the computer. The quality
difference is however quite noticeable on just about any "difficult" track
I tried, and the "high quality" sound files take the same space on one's
hard disk as the "normal" ones. [My usual encoding technique is to copy
an hour's worth of tracks from CD to my hard disk (using a great little
freeware program called "Track
Thief" which is also a good CD player — Track
Thief will "rip" tracks at the maximum speed of your CD player, which
is 24x faster than real time on my machine), then start batch encoding
before I go off to lunch, dinner, or the library.]
-
"advanced" settings: these include
-
a choice between "mono", "stereo", and "joint stereo", Mono speaks for
itself; its use is recommended for recordings that are mono to begin with
(e.g. historical classical or jazz recordings), for modern recordings that
have very little stereo image (e.g. solo guitar or violin), or for intrinsically
low-fi recordings like folk music compilations or (l'havdil)
the Sex Pistols' "Never mind the bollocks". Mono
encoding cuts the size of the MP3 file in half. "Joint stereo" attempts
to discriminate between common information and differences between left
and right channels. This should yield better results for music that has
only limited stereo separation (since the encoding will be almost like
using all 128kbps on a single channel), but is not recommended for music
with strong stereo separation, or which contains sound effects that rely
on stereophony (as are common in electronic music recordings) — you will
hear annoying stereo flutter. In most cases, just plain "stereo" (separate
encoding of each stereo channel) is the setting of choice.
Belay that: I have experimented a bit with "joint stereo" and it
appears that for 128 kbps encoding, it is never worse than stereo
encoding and often better. AudioCatalyst picks "joint stereo" as the
default at 160 kbps and below, and "stereo" above that.
-
VBR (Variable Bit-Rate) encoding. In VBR encoding, a frame is encoded repeatedly
with increasingly higher bit rates until distortion is lower than a specified
tolerance (adjustable in N2MP3 with a "quality" slider). [The lowest bit
rate attempted is the one selected in the main settings panel.] Usually
128 kbps is taken as the starting point, but sometimes 160 kbps.
The advantage is that in music which varies in
sonic complexity, one obtains similar qualities to high bit-rate settings
without the waste of disk space. I just listened to some previews of the
new Steely Dan album, which were encoded VBR (baseline 160 kbps). The files
take 1.5 MB per minute of music, but --- listening through fancy headphones
plugged directly into my computer --- the sound quality is just awesome.
The disadvantage is that only a limited
number of MP3 players will correctly play back VBR files.
Miscellaneous tips
If you are using external "multimedia speakers", crank up the sound volume
on your Mac and turn down the volume on the speakers to compensate. This
will minimize noise and hiss from the usually rather low-fi amplifier in
these speakers.
If a CD starts skipping during copy and/or encode, don't panic. Usually
the problem can be remedied by cleaning the CD with soft cotton and water.
(Be gentle.) Tricks
for repairing more persistent skips can be found at the Learn2
site.
Using Track Thief, you can save several CD tracks together as a single
AIFF (uncompressed CD sound) file, which you can then encode at one go.
I tend to do this for albums I like to hear at one stretch (say, Genesis'
The
Lamb lies down on Broadway, Donald Fagen's The nightfly, Chick
Corea's Children's songs, Klaus Schulze's Mirage) or
for multi-part classical pieces (e.g. all movements of a Beethoven piano
sonata as one MP3, or a prelude and fugue pair in J.S. Bach's Well-tempered
clavier).
One "audiophile" solution that costs about the same as a pair of good
computer speakers and gives much better quality is to buy a pair of Sony
[or other quality brand]
wireless headphones. (We paid $65 for ours at the duty-free in the airport;
presumably they'll be a bit more expensive around the country.)
Since the base unit has its own pre-amp, you can plug
that straight into the computer. A bit of fiddling with the volume controls
on computer and headphones (as always, the stronger the signal into the
amp, the better the signal-to-noise, but the weaker, the less distortion ---
the optimum is somewhere in the middle) and off you go.
Links
MP3
music software for Macintosh
Comparative review of MP3 encoders for Macintosh
Another such review; another relevant site
NEW MacDigitalAudio.com site
NEW DropMP3, a brand-new implementation of the (anything but) LAME MP3 encoder
Another such site
MP3meta search engine.
Another MP3 on
a Mac page.
Comments? Write comartin@wicc.weizmann.ac.il
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