Apple Lossless also known as Apple Lossless Encoder is an open audio codec for lossless compression of digital music developed by Apple in 2004. Audio data is stored in an MP4 container with m4a extension. This codec is similar to other lossless codecs such as FLAC. Every year this format becomes more popular as it is used in iTunes and in all media devices from Apple.
AC3 or Dolby AC-3 is a data format file where six audio channels are compressed by the AC3 codec, also known as Audio Codec 3. The AC3 format is used for the following audio formats - DVD, Blu-ray, cinemas and game consoles. To play the full surround sound of the AC3 file signal, you need a device that supports Dolby Digital technology.