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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