MP3

MPEG-1 Audio Layer 3, or better known as MP3 is a file format that has a voice compression coding a good (albeit lossy) so the file size can be allowed to be smaller. This file was developed by a German engineer Karlheinz Brandenburg. MP3 encoding using Pulse Code Modulation (PCM). MP3 reduces the number of bits required using psychoacoustic models to eliminate the noise components that are not audible by humans.

MP3 wearing a hybrid transformation to transform the signal in time domain into signals in frequency domain:

Filter 32-band polyphase quadrature

36 or 12-MDCT (modified discrete cosine transform), with sizes can be selected independently for sub-band 0 ... 1 and 2 ... 31

Postproses aliasing reduction

MPEG-1 standard does not specify the specifics of how to encode MP3. In contrast, the algorithm and decode the file format is defined specifically. Who want to implement should make their own MP3 encoder algorima to remove part of the information in an audio file of origin (or the MDCT representation in the frequency domain).

Therefore, the MP3 encoder to encode each different and produce different quality results as well. The thing to note is that of all the existing encoder, there is a good encoder for high bitrate and encoder are great for low bitrates.

MP3 has a few restrictions / limits:

Bit rate is limited, a maximum of 320 kbit / s (several encoder can produce a higher bit rate, but very little support for mp3-mp3 is that having a high bit rate)

Time resolution used mp3 can be too low for the voice signals are very transient, so it can cause noise.

Frequency resolution is limited by the length of the window size is small, reducing the coding efficiency

No scale factor band for frequencies above 15.5 or 15.8 kHz

Mode jointstereo done on a per frame

Delay for the encoder / decoder is not defined, so there is no incentive for gapless playback (audio playback without gaps). However, some encoders such as LAME can add additional metadata that provides information to the MP3 player to overcome it.