BENEFITS of MP3:

1. Store up to 10 hours of MP3 music on a CD (compared to a maximum of 80 mins on a standard audio CD)

2. Download, transfer, and storage sizes and times are efficient. An audio .wav file of a CD track might be 30mb +, where an Mp3 file of the same track might total around 3mb.

3. MP3 makes the home computer a digital jukebox—making it much easier to manage, listen and add to your music collection.

4. MP3 personal CD players are also compatible with standard CDs.

5. MP3 is now compatible with a huge range of other music products such as CD players, Minidisc players and Hi-Fi systems. You can burn MP3 files onto a CDR and playback on an MP3 compatible personal CD player, or copy an MP3 direct from a PC to a Minidisc for playback on a Hi-Fi or a personal NetMD/HiMD player.

6. Searchterms.com claim that MP3 is one of the most popular search terms, second only to sex.

7. MP3 enjoys very significant and extremely wide popularity and support, not just by end-users and software but by hardware such as DVD players.

FEATURES for OWNERS:
MP3 enjoys very significant and extremely wide popularity and support, not just by end-users and software but by hardware such as DVD players.

Many listeners accept the MP3 bitrate of 128 kilobits per second (kbit/s) as near enough to CD quality for them; this provides a compression ratio of approximately 11:1, although listening tests show that with a bit of practice, many listeners can reliably distinguish 128 kbit/s MP3s from CD originals.

Decoding of MP3 audio is carefully defined in a standard. Most decoders are "bitstream compliant", meaning that they will each produce exactly the same uncompressed output from a given MP3 file. Therefore, for the most part comparison of decoders is almost exclusively based on how efficient they are -- that is, how much memory or CPU time they use in the decoding process.

FEATURES for PUBLISHERS:
IF further operating on it is necessary, original audio data should best be kept in its original state. If any operation needs to be done on mp3 data, such as cutting or merging audio, or lowering bitrate, it is preferable to use software dealing directly with the mp3 data stream (such as mp3DirectCut and MP3Gain) and prevent extra decoding-encoding steps. If MP3 audio needs to be decoded and re-encoded another time, for example when it will be aired on radio, "stacking" of one lossy compression stage on top of another one will do no good to the quality of the end-result.

Variable bit rates are also possible.
Audio in MP3 files are divided into frames which all have a bitrate marker, so it is possible to change the bitrate dynamically as the file is played. This was not originally done, but VBR is in extensive use today. This technique makes it possible to use more bits for parts of the sound with high dynamics (much "sound movement") and less bits for parts with low dynamics, increasing quality and decreasing storage space further. This method compares to a sound activated tape recorder which saves the tape space from when silence was prevalent for the times when sound is being heard. Some encoders utilize this technique to a great extent.

The MPEG-1 standard does not include a precise specification for an MP3 encoder. The decoding algorithm and file format, as a contrast, are well defined. Implementors of the standard were supposed to devise their own algorithms suitable for removing parts of the information in the raw audio (or rather its MDCT representation in the frequency domain). This is the domain of psychoacoustics, which aims at understanding how human acoustical perception works (both in our ears and in our brain).

As a result, there are many different MP3 encoders available, each producing files of differing quality. Comparisons are widely available, so it is easy for a prospective user of an encoder to research the best choice. It must be kept in mind that an encoder that is proficient at encoding at higher bitrates (such as LAME, which is in widespread use for encoding at higher bitrates) is not necessarily as good at other, lower bitrates.

A "tag" is metadata stored in an MP3 (and other formats) such as the title, artist, album, track number or other information about the MP3 file to be added to the file itself. The currently most widespread standard tag formats are the ID3 ID3v1 and ID3v2 tags, and the more recent APEv2 tag.

SPECIFICATIONS:
The quality of MP3 depends on the quality of the encoder and the difficulty of the signal which must be encoded. Good encoders produce acceptable quality at 128 - 160 kbit/s. Near transparency is achieved at 160 - 192 kbit/s. Low quality encoders may never reach transparency, not even at 320 kbit/s. So it is pointless to speak of 128 kbit/s or 192 kbit/s quality. A 128 kbit/s MP3 produced by a good encoder might sound better than a 192 kbit/s MP3 file produced by a bad encoder.

An important feature of MP3 is that it is lossy — meaning that it removes information from the input in order to save space (and bandwidth cost). As with most modern lossy encoders, MP3 algorithms work hard to ensure that the parts it removes cannot be detected by human listeners, by modeling characteristics of human hearing such as noise masking. The importance of this is that it can gain huge savings in storage space with reasonable and acceptable (although detectable) losses in fidelity.

As a form of compression, MP3 is based on a psycho-acoustic model which recognizes that the human ear cannot hear all the audio frequencies on a recording. The human hearing range is between 20Hz to 20Khz and it is most sensitive between 2 to 4 KHz. When sound is compressed into an MP3 file, an attempt is made to get rid of the frequencies that can't be heard. As such, this is known as 'destructive' compression. After a file is compressed, the data that is eliminated in the creation of the MP3 cannot be replaced.

In technical terms, MP3 is limited in the following ways:

• bitrate is limited to a maximum of 320 kbit/s
• time resolution can be too low for highly transient signals
• encoder/decoder overall delay is not defined
• no scaleband factor for frequencies above 15.5/15.8 kHz
• joint stereo is done on a frame-to-frame basis

Dynamically adjusted volume:
As CDs and other various sources are recorded and mastered at different volumes, it is useful to store volume information about a file in the tag so that at playback time, the volume can be dynamically adjusted. The idea is to normalize the volume, not the peaks, of files replayed after each other, so that the volume does not fluctuate up and down between tracks, harming the listening experience.

HISTORY:
MP3 is the shortened name for MPEG-1 Layer III (or MPEG Audio Layer III) and is an audio subset of the MPEG industry standard developed by ISO (the Industry Standards Organization) and became an official standard in 1992 as part of the MPEG-1 standard.

Fraunhofer Gesellschaft (FhG), a German company was the company originally involved in MP3 development and holds key patents regarding the technology.

MPEG-1 Layer III is an audio only compression component and is a direct descendant from MPEG-1 which is low-bandwidth video compression, the type that is used over the internet and MPEG-2 which is a high-bandwidth audio and video compression which is the standard for DVD technology.

1987 - Development of MP3 started in Germany at the Fraunhofer Institut Integrierte Schaltungen and its given name was the EUREKA project EU147, Digital Audio Broadcasting (DAB). This project was financed by the European Union. With the involvement of Professor Dieter Seitzer of the University of Erlangen an algorithm was developed and eventually became known as the ISO-MPEG Audio Layer-3 standard.

EU-147 ran from 1987 to 1994.
In 1991 there were two proposals available: Musicam (known as Layer II) and ASPEC (Adaptive Spectral Perceptual Entropy Coding) (with similarities to MP3). Musicam was chosen due to its simplicity and error resistance.

1988, January saw MPEG itself established, its full title Moving Picture Experts Group, not an organization in itself, but a subcommittee of the ISO/IEC (International Standards Organization/International Electrotechnical Commission).

A working group around Karlheinz Brandenburg and Jürgen Herre took ideas from Musicam and ASPEC, added some of their own ideas, and created MP3, which was designed to achieve the same quality at 128 kbit/s as MP2 at 192 kbit/s.

1989, April - Fraunhofer received a patent for MP3 in Germany and in 1992 Fraunhofer’s algorithm was integrated in MPEG-1 for which the specification was published in 1993.

1992 - Both algorithms were finalized as part of MPEG-1, the first phase of work by MPEG, which resulted in the international standard ISO/International Electrotechnical Commission 11172-3, published in 1993. Further work on MPEG Audio was finalized in 1994 as part of the second phase, MPEG-2, which resulted in the international standard ISO/IEC 13818-3, originally published in 1995.

1993, October - MP2 (MPEG-1 Audio Layer 2) files appeared on the Internet and were often played back using Xing MPEG Audio Player, and later in a program for UNIX by Tobias Bading called MAPlay initially released on February 22, 1994. (MAPlay was also ported to Microsoft Windows.)

1994 - MPEG-2 and its specification was published the following year in 1995.

1995, January 26th, saw Fraunhofer apply for the patent of MP3 in the USA and was granted it on November 26th, 1996.

1998, September - Fraunhofer contacted independent developers of MP3 encoders (rippers) and decoders (players) that were based on the ISO source code. Fraunhofer had patent protection on the algorithm they were using and developers who wanted to develop their software applications further would have to apply to Fraunhofer for licence.

Sub Pop, an independent record label began in February 1999 to distribute selected music tracks in the MP3 format.

Since the beginning of 1999 the popularity of MP3 has increased to such an extent that major manufacturers are flooding the market with portable MP3 players, the next step on from the Walkman and Portable CD and Mini Disc players. Music sites are springing up everywhere on the internet offering free legal MP3 music and also music to purchase.

OTHER RESOURCES:

The History of MP3 and how it all began.:
http://www.mp3-mac.com/Pages/History_of_MP3.html

MP3 on Wikipedia:
http://en.wikipedia.org/wiki/Mp3

MP3 Portal by Mpeg.org:
http://www.mpeg.org/MPEG/mp3.html

Blade MP3 Encoder:
http://bladeenc.mp3.no/