The Ups and Downs of Audio Format Selection

Audio Format Selection

Lossy or lossless? MP3 or WMA? Here are the pros and cons of the most common digital audio formats.

Apr. 02, 2008 — by .(JavaScript must be enabled to view this email address)

The digital music revolution was supposed to make our lives easier, wasn’t it? Music that follows you wherever you go, easy-to-use playlists, massive amounts of tunes in the palm of your hand—it all sounds so deliciously enticing until you try to decide what form you want that digital music to take. Do you want your music stored in lossy or lossless format? What does that even mean? Is disk-space more important to you than sound quality? Or would you rather have better sound, at the expense of being able to store fewer songs. Or are both of those qualities secondary to being able to rip (or buy) your music once and play it on virtually any audio device you can get your hands on?

The choices are so numerous that a beginner might be inclined to run screaming back to the safety of CDs. The following brief breakdown of the most common digital audio formats—with emphasis on the strengths and weaknesses of each—should clear up some of the confusion and allow even the greenest of neophytes to pick the right format to meet his or her needs.

AAC (Advanced Audio Coding): Although most often associated with the iPod, this MPEG-4 audio format was actually poised by its creators (including Bell Laboratories, Dolby, Fraunhofer, Nokia, and Sony—not Apple) as the universal successor to the aging-but-popular MP3 format. 

AAC is a lossy audio codec (coder-decoder), meaning it uses complex calculations based on the strengths and weaknesses of human hearing to remove (or lose) unimportant information from the original audio source. This greatly reduces the size of an audio file without noticeably impacting audio quality for most listeners. For example, at a bitrate of 192 kilobits per second (kbit/s), the point at which most people cannot distinguish a song encoded with AAC from the CD, the AAC file will chew up less than 15% of the disk space as the original.

The Highs: More sophisticated and efficient than MP3, meaning it can generate equal or better sound quality without hogging as much disk space. Supported by virtually all name-brand personal digital music players and current-generation game consoles, as well as many software players, distributed audio servers such as Escient Fireballs, and wireless music systems made by Sonos and SqueezeBox. 

The Lows: Unsupported by popular ReQuest music servers. Also can’t be streamed to a Windows Media Center Extender without a lot of fuss and unofficial add-on programs. Advantages over MP3 diminish at higher bitrates. AAC files purchased from iTunes before the advent of iTunes Plus come with pesky copy protection that limits how, where, and on which devices you can play the music.

FLAC (Free Lossless Audio Codec): As its name implies FLAC differs from AAC (and MP3, Ogg Vorbis, WMA, and many other codecs) in that it offers lossless audio compression. Instead of forever removing audio information from the file to save disk space, such lossless codecs simply find different ways of packing the digital information more efficiently, while still being capable of recreating the original audio signal bit-for-bit. For example, you can generally expect FLAC to reduce the disk space required for full CD-quality audio from 1411 kilobits per second of audio down to 700 to 800 kbit/s—a 40-50% reduction, depending upon the complexity of the music. And again, this is with absolutely no reduction in quality, perceived or otherwise.

The Highs: Produces a sonically perfect recreation of your CDs, while still reducing disk space as compared to uncompressed formats such as WAV and AIFF. Open source, so it’s available on many platforms. Supported by music servers from both Escient and ReQuest, popular wireless music systems from Sonos and SqueezeBox, as well as many popular software players like WinAmp, MediaMonkey, and AlbumPlayer. Playback is also faster and less processor-intensive than many other lossless audio formats. 

The Lows: Limited support on personal digital music players, unless you want to resort to unsupported (and potentially dangerous) third-party firmware. Not recognized by music management programs that most people use: iTunes, Windows Media Player, etc. 

MP3: The granddaddy of all lossy digital music codecs, MP3 isn’t going anywhere soon. In fact, its name has become synonymous with the whole concept of digital music. Think about it: have you ever heard a kid ask for an AAC or WMA player for Christmas? An Ogg Vorbis player? I thought not. These days, if it makes noise, it’s pretty safe to assume that it supports MP3. Due to name recognition alone, the format will most likely outlive many of the codecs intended to replace it, superior though they may be. 

The Highs: The format you’re most likely to use, no matter what you read in this article. Sounds perfectly fine to the vast majority of people at bitrates of 128 kbit/s and above. Nigh-universal support, due to its massive installed base: MP3s can be played by just about every music player, computer program, toaster, tennis shoe, pack of gum, and gaming console in the world (except, interestingly enough, the Wii, which just scrapped MP3 playback in favor of AAC exclusivity).  Its lack of DRM (digital rights management, or copy protection) also leads to fewer playback hiccups and compatibility issues. 

The Lows: Inefficient compared to other lossy codecs, and potentially a waste of disk space at the very highest bitrates, depending on the encoder you use. Even at those highest bitrates, MP3 has a hard time with certain sounds, like cymbals, drums, and applause. And at the lowest useable bitrates, MP3 performs significantly worse than AAC, Ogg Vorbis, and other, newer lossy codecs. Also, the loose specifications for MP3 encoders can lead to some confusion, as well as huge debates over minute differences in the quality of files generated by different encoders. 

Ogg Vorbis: Designed as an open-source alternative to/replacement for MP3 and initially released in 2002, Ogg Vorbis has quickly become the audio codec equivalent of a cult classic. Unlike many lossy codecs, Vorbis offers only variable-bitrate encoding (VBR, an option with most MP3 and AAC encoders), meaning that users select a preferred quality setting instead of a bitrate, and the encoder constantly varies the bitrate in relation to the complexity of the audio signal. 

The Highs: Major brownie points for being named after a character from Terry Pratchett’s Discworld series, as well as being completely DRM-free. Widely considered by many critical listeners to be the lossy codec with the best sound quality by a wide margin, especially at higher bitrates. Well supported on Linux. Widely used in the video game industry. Supported by ReQuest’s music servers, Sonos and SqueezeBox wireless music systems, and popular software players like MediaMonkey, AlbumPlayer, and WinAmp (after installing the appropriate plugin).

The Lows: Not supported by Escient audio servers and the vast majority of personal digital audio players, such as the iPod and Zune. Getting iTunes and Windows Media Player to recognize the format requires a bit of tinkering. 

WMA (and WMA Pro, WMA Lossless): Windows Media Audio got off to a bit of a rocky start thanks to some spurious statements by Microsoft, who claimed that WMA generated CD-quality audio at a mere 64 kbit/s (a claim handily refuted by anyone with two ears and some without). In the intervening years, though, WMA has been widely embraced, and is nearly as widely supported as MP3 these days. 

WMA comes in a few different varieties. In addition to the recent improvements of the original WMA codec, Microsoft has developed WMA Pro—which supports better-than-CD-quality audio—as well as their own lossless format dubbed, creatively enough, WMA Lossless. The only problem with this is that the three formats share little in common, other than their names and file extension. In fact, any real examination of the differences between them—from the way their work to the devices that support them—would require an article unto itself. 

The Highs: High quality audio playback. Significant improvements over the years. Standard WMA files are nearly as universally supported as MP3, with playback available on many personal digital audio players, wireless music systems, and software players. May well be the perfect format for those who own the Zune and use entirely Microsoft-based music distribution systems. WMA Pro offers extremely high-quality surround sound playback, with sampling rates up to 96kHz (more than twice the sampling rate of CD audio). And WMA Lossless offers the same bit-for-bit recreation of the original file, while on average taking up less disc space. 

The Lows: Unsupported by popular ReQuest music servers, as well as iTunes and iPod. Pro and Lossless aren’t nearly as widely supported as standard WMA, which can lead to confusion since all three formats use the same .wma file extension. Digital rights management can also lead to compatibility issues and playback problems, and certainly don’t do anything to ameliorate Microsoft’s Big Brother perception among some users.

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