I'm pleased to share my success with a project I first began in June of 2019 but had shelved until today! I'd constructed an ambient playlist on my server of ~130,000 tracks for background listening which I enjoy for an average of 19 hours each day while I work and while I sleep. Unfortunately I found that many tracks were mastered with considerable differences in signal processing / dynamic range compression / equalization. The result was that some albums had a perceived loudness far greater than others, which disturbed my concentration and my rest.
Thankfully, a bit of research revealed that I was not alone with this concern, and that digital audio engineers addressed the issue by incorporating a feature into the ID3v2 standard outlined by hydrogenaudio as the "replaygain 1.0 specification."
Most digital music library software applications feature a replaygain function, permitting the user to apply, automatically or manually, gain adjustment values stored in the metadata of the music file to nudge the volume up or down as required, and my Linux desktop audio software was among them.
Automatic loudness measurement, (the formula for which is available on the hydrogenaudio wiki), can be applied to selected tracks individually, or to the loudness of an overall album. The album option, hydrogenaudio notes, "leave(s) the intentional loudness differences between tracks in place, yet still correct for unmusical and annoying loudness differences between albums."
The challenge was to find a mobile media server client which retained and interpreted the replaygain values during transcoding. I experimented with various mobile applications to find one which natively supported both gapless playback and replaygain.
Researching forum discussions on the subject lead me to an independent fork of my preferred media server application available for Android. The project was a success! After batch processing the replaygain values for the ambient segment of my library, the adjustments I applied to the track metadata were successfully interpreted and rendered during playback in the mobile application!
This small victory will have a profound impact on my daily and nightly listening sessions. I'm so glad I kept my notes and revisited the project!
