Add replay gain support, ref#47

Feature description
According to Wikipedia:
ReplayGain is a proposed standard published by David Robinson in 2001 to measure the perceived loudness of audio in computer audio formats such as MP3 and Ogg Vorbis. It allows media players to normalize loudness for individual tracks or albums. This avoids the common problem of having to manually adjust volume levels between tracks when playing audio files from albums that have been mastered at different loudness levels.

Proposed workflow

  1. User has to add RG-information to the tracks / albums by using 3rd party software, e.g. DbPower amp is able to add RG-information to the tracks without changing the the audio; a RG-aware player uses this information.
  2. User define playlist in MusicLife app and sends it to SA30 with RG enabled. The playlist contains tracks and/or albums with RG-information.
  3. The SA30 interprets the RG-information and applies it.


  1. Refer to Roon’s implementation of volume leveling and using loudness data in REPLAYGAIN tags.
  2. R128GAIN is a FFmpeg and SoX based EBU R128 compliant loudness scanner, refer to here