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MP3 / FLAC SOUND COMPRESSION.
by Allen Dyke

Allen Dyke

MP3 is a patented 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 standard of digital audio compression for the transfer and playback of music on digital audio players.MP3 is an audio-specific format that was designed by the Moving Picture Experts Group as part of its MPEG-1 standard. The group was formed by several teams of engineers at Fraunhofer IIS in Erlangen, Germany, AT&T-Bell Labs, Thomson-Brandt, and CCETT as well as others. The use of MP3 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.

An MP3 file that is created using the setting of 128 KB will result in a file that is about 1/11 the size of a commercial 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 psychoacoustic models to discard or reduce precision of components less audible to human hearing, and recording the remaining information in an efficient manner.
Therefore mp3 gains most of its reduction in file size by chucking away information. If recorded at 128kbps, a piece of music would be 1mb for each playing minute.  This is 1/11th of the size when recorded on a commercial CD. This bit rate is regarded as the optimum to preserve a good quality signal which to most people is unrecognisable from the original even on top of the range audio equipment. The only thing I can detect is a slightly confused sound on very complexed loud music. There are a number of recording rates. At 64kbps the sound has definitely deteriorated but when it is recorded at 128kbps or higher, the quality shows a dramatic improvement. Basically the lower the number of kilo bits per second the more the sound deteriorates but the resulting file becomes smaller.
My MP3 player which is 4 GB in memory size holds 1400 tracks of popular music. The sound quality being far superior to the old cassette tapes.

 FLAC stands for Free Lossless Audio Codec, a leading compression technique that preserves original audio quality while reducing file size. FLAC is an open-source, royalty-free format that has been adopted widely for its many advantages in digital audio reproduction.
Compression techniques take large files such as wave (.wav) files such as CD audio and reduce the data bits while preserving as much of the audio landscape as possible. A well-known audio compression format is MP3 (.mp3). MP3 files slim down bulky wave and compact disk (.cad) files to a fraction of their original size, making MP3 an ideal format for portable audio players. The MP3 format allows a vast library of songs to fill a very small storage footprint. However, there is a trade-off in audio quality.
FLAC surpasses MP3 quality by preserving the original soundscape in exact detail. The FLAC format reduces the original file size by roughly 30-60% with no loss of quality; hence it is a lossless format. This differs from the MP3 format which is a Lossy format, or a format that loses quality in the conversion process because information is discarded.
One of the great strengths of FLAC is its very fast decoding time, or ability to stream even on modest hardware. Technical specifics in the framed architecture also allow it to be error resistant, in that each frame has the information it needs to decode itself. If a frame is corrupted, the data lost in the stream is a mere blip. This differs from other types of lossless formats where the entire stream would essentially become corrupted.

Another feature of FLAC is that it can handle up to eight channels of audio for preserving surround sound recordings. FLAC is also a good choice for archiving audio CDs, as one can always use the FLAC file later to convert to future formats. A further advantage of FLAC is that it supports replay gain, a technique for ensuring that recorded sound files play at the same volume level. Many tracks of music are recorded at many different volume levels.

The only real disadvantage of FLAC files is that the compression ratio is not as steep as other codec’s. Files will be somewhat larger at around 5MB per minute. However, with all of the advantages of FLAC, this is a happy trade off for many audiophiles.

Considering the falling prices of flash cards, portable players, and storage devices, the FLAC format will likely only gain support. FLAC files can play on iPods and other portable devices, and on home or car compact disk players that support FLAC.
   

Allen Dyke

High Definition Video a quick look
SSD versus HDD
MP3 / FLAC Sound Compression
High Defintion
Part One
Cleaning Hard Drives
Hard Drive Installation
GUIDANCE NOTES ON COMPETITION FILMS
MUSIC COPYRIGHT
BOB'S BASIC EDITING GUIDE
A Novel Camera Support
DOWNLOAD ADOBE PREMIERE 6.5 EDITING GUIDES
Adding Filters
Create a Freeze Frame
Correcting Synch Errors
Change Capture Location