ALAC is the format of a small specialized program called an audio codec. Its main task is to compress a file with digital music without losing its quality. The name of the format created by Apple's IT giant is Apple's abbreviation Lossless Audio Codec. This format may also be called ALE (from Apple Lossless Encoder). Files in this format can play devices even with limited computing resources - such as an iPod. When compressing a file in this format, it is approximately 40-60% of the original file. Now almost every multimedia player based on the libavcodec library is able to play ALAC format files.
AC3 is a sound file format. Its name is the abbreviation for Audio Codec 3. The format was developed by Dolby Laboratories, Inc as a modern and efficient sound compression technology. AC3 files feature Dolby Digital multi-channel surround sound. In this regard, they are widely distributed as a format for DVDs, movie theaters and game consoles. However, you can evaluate all the advantages of such files only if you have the appropriate acoustics for surround sound. An audio file of the specified format can include up to six sound channels, which creates a presence effect for the listener.