All Is Not Lost

Oct 1, 2006 12:00 PM, By Vijith Assar

           

Trust the Experts

Modern versions of LAME include several different parameter presets that optimize encoding based on audio quality rather than file size. Ultimately, that's a much more useful metric of performance, and LAME undergoes extensive psychoacoustic testing before each release in order to make it possible. Early pro-MP3 claims promised perceptual transparency at bit rates as absurdly low as 128 kbps; this was soon found to be poppycock. LAME's “ — alt-preset-standard” (APS) option promises the same but is much more likely to deliver. APS is widely regarded as the new standard for MP3 encoding and works by analyzing the source file to determine the least destructive ways it can save bits. It then trims the file size through a combination of filters, noise shaping, and joint stereo representation.

FIG. 4: You can set options in LAME and many other encoders by using special command-line settings, such as those shown here.

LAME offers other presets as well. APE, or “ — alt-preset-extreme,” applies the same principles as APS using a slightly higher threshold of perceptual transparency. (The developers insist that the differences are merely theoretical and probably aren't audible to everyone.) API, or “ — alt-preset-insane,” is functionally equivalent to the “ — cbr 320” command, as it encodes every audio frame at the highest quality level allowed by the MP3 specification.

More recent releases of LAME have moved from using text string — based preset names to a numeric system in which lower numbers mean higher audio quality; “ — v2” is the new APS and “ — v0” is the new APE. Currently, both naming conventions will work, and both map to the same presets (see Fig. 4). That may change in future revisions of LAME, however.

Meet Your Arsenal

Many new digital audio sequencers include the ability to export mixes in a compressed format, but because they don't always support the more advanced encoding options, you may have to look elsewhere. In addition to having the tagging capabilities discussed earlier, Panic's Audion is a very capable OS X front end for LAME. There is also an AppleScript for the OS X version of iTunes called iTunes-LAME, developed by Blacktree, that overrides the default encoder and uses LAME instead, with all the special command options intact. Note that you have to start the importing process from the AppleScript menu in order to use LAME; using the normal buttons in iTunes will enable the default encoder.

FIG. 5: Many Windows programs, including Winamp, can be used as front ends for a number of different encoders.

In Windows, LAME can be accessed through a number of different programs, including Nullsoft's Winamp, Albert Faber's CDex, Illustrate's dBpowerAmp, and Andre Wiethoff's Exact Audio Copy. Unlike iTunes, which ships with its own built-in encoders, these programs can perform encoding tasks by accessing outside programs, so they can be used to compress files in any of the other formats mentioned earlier (see Fig. 5). Perhaps the most robust of all is Peter Pawlowski's free foobar2000, an astonishingly deep Windows-only program that is the Swiss Army knife of compressed audio.

Choose Your Weapon

Lossy audio codecs can sound very different, and if you're planning to use compressed files internally, pick a format based on your specific needs, then tailor the compression settings around the results of your own listening tests. If you are compressing your files in order to share them with clients and potential customers, stick with MP3 for compatibility, but consider using the LAME encoder with one of the high-quality VBR presets to get a sonic edge on the competition.

No matter what encoding methods you use, though, keep your original high-resolution files handy. If you eventually need to switch to another format, you won't want to transcode from one lossy audio format to another, as this just compounds the fidelity loss. Instead, you'll need to recompress from the original WAV or AIFF file, or rerip the tracks from the source CD. (You can't use a CD burned from lossy files as a source, because your system can't magically restore the data that was lost when those files were compressed.)

Although the most recent wave of audio formats allows for lossless compression that does not compromise fidelity at all, compatibility concerns and the need for rapid Internet file transfers mean that lossy compressed audio files still have a place in every musician's studio. Don't be afraid to experiment with the many available compression tools to determine which works best for you. With a little technical savvy, you'll be amazed at how good a modern encoder can sound.

Vijith Assar works at the Music Resource Center in Charlottesville, Virginia, and writes for the local newspaper. Visit him online at www.vijithassar.com.

MANUFACTURER CONTACTS

Blacktree www.blacktree.com/apps/iTunes-LAME

Albert Faber http://sourceforge.net/projects/cdexos

Illustrate www.dbpoweramp.com

Nullsoft www.winamp.com

Panic www.panic.com/audion

Peter Pawlowski www.foobar2000.org

Andre Wiethoff www.exactaudiocopy.de