Apple unveils the source of audio codec "ALAC" that does not degrade sound quality


Apple has released the source of the audio codec "Apple Lossless Audio Codec (ALAC)" adopted by many of its products.

Apple Lossless Audio Codec

Apple, Open Source "Apple Lossless" - Phile-web

"ALAC" is a lossless compression lossless audio codec that does not degrade when compressing music and sound, and it is adopted in iPhone, iPad, most iPod, Mac, iTunes.

The standard for compressing music is based on the audio standard developed by Windows "Windows Media Audio"And music players and other widely used"MP3Although there are many such as "Why is the size shrinking, because it cuts out the sound of sounds that human beings can not hear.

These formats are called lossy compression format because returning the file to its original form does not return the cut data. If you treat the CD as data without compressing it, the capacity will be about 700 MB with one disk, which is not suitable for handling on a PC very much. Therefore, as the size decreases, and as far as you listen with your ears, MP3 etc. that sound quality does not change so much are used.

However, in theory it should be unknown about its deterioration, but when you listen to the sound, the sound quality is degraded. Therefore, there is a lossless compression format that can be compressed without cutting the range.

In order to actually use ALAC, choose "Apple lossless encoder" from the setting when importing CD in iTunes OK. With this, the CD is imported to the PC in ALAC format.

Since it is lossless compression, the data before compression and the data expanded once compressed are equal. The degree of compression is an excellent one that can reduce the size to about 50% in WAVE format or AIFF format.

The data released this time includes the ALAC encoder and decoder source, as well as a utility called "alacconvert" that can compress and expand CAF or WAVE format by command line.

By the way, the source code is "Apache License, Version 2.0Distribution is being done in. Under this license, there is no particular restriction on the use of software, redistribution, modification, distribution of derivative works. Although copyright indication and indication of disclaimer are necessary, different licenses can be given for parts modified by oneself.

The source code can be downloaded from the following page.
Apple Lossless Audio Codec Download

in Note, Posted by darkhorse_log