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Competing technologies
Many other lossy audio codecs exist, including:
MPEG-1/2 Audio Layer 2 (MP2), MP3's predecessor;
Ogg Vorbis from the Xiph.org Foundation, a free software and patent free codec.
MPC, also known as Musepack (formerly MP+), a derivative of MP2;
mp3PRO from Thomson Multimedia combining MP3 with SBR;
AC-3, used in Dolby Digital and DVD;
ATRAC, used in Sony's Minidisc;
MPEG-4 AAC, used by Apple's iTunes Music Store and iPod
Windows Media Audio (WMA) from Microsoft.
QDesign, used in QuickTime at low bitrates;
AMR-WB+ Enhanced Adaptive Multi Rate WideBand codec, optimized for cellular and
other limited bandwidth use;
RealAudio from RealNetworks, frequently in use for streaming on websites;
Speex, free software and patent free codec based on CELP specifically designed
for speech and VoIP.
mp3PRO, MP3, AAC, and MP2 are all members of the same technological family and
depend on roughly similar psychoacoustic models. The Fraunhofer Gesellschaft
owns many of the basic patents underlying these codecs, with Dolby Labs, Sony,
Thomson Consumer Electronics, and AT&T holding other key patents.
There are also some lossless audio compression methods used on the Internet.
While they are not similar to MP3, they are good examples of other compression
schemes available. These include:
FLAC stands for 'Free Lossless Audio Codec'
Monkey's Audio
SHN, also known as Shorten
TTA
Wavpack
Apple Lossless
Listening tests have attempted to find the best-quality lossy audio codecs at
certain bitrates. At 128kbit/s, Ogg Vorbis, AAC, MPC and WMA Pro tied for first
place with LAME MP3 a little behind. At 64kbit/s, AAC-HE and mp3pro performed
marginally better than other codecs. At high bitrates (128kbit/s+), most people
do not hear significant differences. What is considered 'CD quality' is quite
subjective; for some 128kbit/s MP3 is sufficient, while for others 200kbit/s or
higher MP3 is necessary.
Though proponents of newer codecs such as WMA and RealAudio have asserted that
their respective algorithms can achieve CD quality at 64 kbit/s, listening tests
have shown otherwise; however, the quality of these codecs at 64 kbit/s is
definitely superior to MP3 at the same bitrate. The developers of the
patent-free Ogg Vorbis codec claim that their algorithm surpasses MP3, RealAudio
and WMA sound quality, and the listening tests mentioned above support that
claim. Thomson claims that its mp3PRO codec achieves CD quality at 64 kbit/s,
but listeners have reported that a 64 kbit/s mp3PRO file compares in quality to
a 112 kbit/s MP3 file and does not come reasonably close to CD quality until
about 80 kbit/s.
MP3, which was designed and tuned for use alongside MPEG-1/2 Video, generally
performs poorly on monaural data at less than 48 kbit/s or in stereo at less
than 80 kbit/s.
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