MP3 Audio File Format Description:

MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a digital audio encoding format using a form of lossy data compression. It is a common audio format for consumer audio storage, as well as a de facto standard encoding for the transfer and playback of music on digital audio players. MP3 is an audio-specific format that was co-designed by several teams of engineers at Fraunhofer IIS in Erlangen, Germany, AT&T-Bell Labs in Murray Hill, NJ, USA, Thomson-Brandt, and CCETT. It was approved as an ISO/IEC standard in 1991. MP3's use of a lossy compression algorithm is designed to greatly reduce the amount of data required to represent the audio recording and still sound like a faithful reproduction of the original uncompressed audio for most listeners, but is not considered high fidelity audio by audiophiles. An MP3 file that is created using the mid-range bit rate setting of 128 kbit/s will result in a file that is typically about 1/10th the size of the CD file created from the original audio source. An MP3 file can also be constructed at higher or lower bit rates, with higher or lower resulting quality. The compression works by reducing accuracy of certain parts of sound that are deemed beyond the auditory resolution ability of most people. This method is commonly referred to as perceptual coding. It internally provides a representation of sound within a short term time/frequency analysis window, by using sychoacoustic models to discard or reduce precision of components less audible to human hearing, and recording the remaining information in an efficient manner. This is relatively similar to the principles used by JPEG, an image compression format.

When performing lossy audio encoding, such as creating an MP3 file, there is a trade-off between the amount of space used and the sound quality of the result. Typically, the creator is allowed to set a bit rate, which specifies how many kilobits the file may use per second of audio, as in when ripping a compact disc to MP3 format. Using a lower bit rate provides a relatively lower audio quality and produces a smaller file size. Likewise, using a higher bit rate outputs a higher quality audio, and therefore results in a larger file.

Files encoded with a lower bit rate will generally play back at a lower quality. With too low a bit rate, "compression artifacts" (i.e., sounds that were not present in the original recording) may be audible in the reproduction. Some audio is hard to compress because of its randomness and sharp attacks. When this type of audio is compressed, artifacts such as ringing or pre-echo are usually heard. A sample of applause compressed with a relatively low bit rate provides a good example of compression artifacts.

Quality is heavily dependent on the choice of encoder and encoding parameters. While quality around 128 kbit/s was somewhere between annoying and acceptable with older encoders, modern MP3 encoders can provide adequate quality at those bit rates (January 2006). However, in 1998, MP3 at 128 kbit/s was only providing quality equivalent to AAC-LC at 96 kbit/s and MP2 at 192 kbit/s.

Several bit rates are specified in the MPEG-1 Layer 3 standard: 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 192, 224, 256 and 320 kbit/s, and the available sampling frequencies are 32, 44.1 and 48 kHz. A sample rate of 44.1 kHz is almost always used, because this is also used for CD audio, the main source used for creating MP3 files. A greater variety of bit rates are used on the Internet. 128 kbit/s is the most common, because it typically offers adequate audio quality in a relatively small space. 192 kbit/s is often used by those who notice artifacts at lower bit rates. As the Internet bandwidth availability and hard drive sizes have increased, 128 kbit/s bit rate files are slowly being replaced with higher bit rates like 192 kbit/s, with some being encoded up to MP3's maximum of 320 kbit/s. It is unlikely that higher bit rates will be popular with any lossy audio codec because file sizes at higher bit rates approach those of lossless codecs such as FLAC.

Many other lossy and lossless audio codecs exist. Among these, mp3PRO, AAC, and MP2 are all members of the same technological family as MP3 and depend on roughly similar psychoacoustic models. The Fraunhofer Gesellschaft owns many of the basic patents underlying these codecs as well, with others held by Dolby Labs, Sony, Thomson Consumer Electronics, and AT&T.

Audio Transcoder supports the following conversions with MP3 format files:

•  MP3 to AAC
•  MP3 to APE

•  MP3 to FLAC
•  MP3 to M4A
•  MP3 to M4B
•  MP3 to MP4

•  MP3 to MP2
•  MP3 to MP3
•  MP3 to MPC
•  MP3 to OGG

•  MP3 to SPX
•  MP3 to WAV
•  MP3 to WMA

• AAC to MP3
• AC3 to MP3
• AIF to MP3
• APE to MP3
• FLAC to MP3
• M4A to MP3
• MP+ to MP3
• MP1 to MP3
• MP2 to MP3
• MP4 to MP3
• MPC to MP3
• MPP to MP3
• OFR to MP3
• OFS to MP3
• OGG to MP3
• SPX to MP3
• TTA to MP3
• WAV to MP3
• WMA to MP3
• WV to MP3


Note that Audio Transcoder is not only a great Audio Converter. It is all-in-one solution to convert any audio files - WAV, WMA,  MP3,MP3,MP4,  MP3 and many others, rip Audio CD's, edit audio tags.