MP3

MP3 is a popular digital audio encoding and lossy compression format invented and standardised in 1991 by a team of engineers working in the framework of the ISO/IEC MPEG audio committee under the chairmanship of Professor Hans Musmann (University of Hannover - Germany). It was designed to greatly reduce the amount of data required to represent audio, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners. In popular usage, MP3 also refers to files of sound or music recordings stored in the MP3 format on computers.

Alternative 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.

Related Topics:
Psychoacoustic model - Fraunhofer Gesellschaft - Patent - Dolby Labs - Sony - Thomson Consumer Electronics - AT&T

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

There are also some non-lossy (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

Listening tests have attempted to find the best-quality lossy audio codecs at certain bitrates. The tests have suggested that for some audio samples, newer audio codecs including Ogg Vorbis, mp3PRO, AC-3, Windows Media Audio, MPC and RealAudio perform better than MP3. Generally, these codecs achieve the equivalent of MP3 128kbit/s at around 80kbit/s. At 128kbit/s, Ogg Vorbis and MPC performed marginally better than other codecs. At 64kbit/s, AAC 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 192kbit/s 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 bandwidth. 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.

Related Topics:
Ogg - Vorbis

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

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.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~