FLAC file volume

[bluesman]

On 2/18/2021 at 5:38 AM, Anonamemouse said:

The FLAC format does not allow for gain/volume changes "on the fly". This is something that is specified in the player, like (e.g.) Foobar. If you change the volume of a track, it is rewritten. So if you ever want to change the volume of certain tracks, be sure to only use copies of the original track, because the process can NOT be reversed.

The way you state that is not quite correct and could easily be misinterpreted.  You can’t alter the data in a music file while it’s playing, but you can obviously turn the volume up or down ad lib without damaging or changing any audio file.  
 

What cannot be done “on the fly” or reversed after saving the changes and closing the file (not the program - the file) is destructive editing, eg normalizing, equalizing, compressing, and otherwise altering the waveform itself.  
 

There are some nondestructive audio editing programs.  But most (like Audacity, Ardour, and the other widely used DAW and editing programs most of us use at home) permanently alter file content once you save and close the file.  I’m pretty sure that Fairlight (the audio editing part of DaVinci Resolve) is nondestructive and can edit during playback. I haven’t played with it yet, but it’s next on my list of editing programs to try as I prepare a review and comparison of audio editing tools for audiophiles.
 

Replay gain is based on scanning tracks and using an algorithm to calculate a “score” reflective of amplitude, range, and central tendency measurements of the relative loudness of each (eg mean, median, peak envelope etc as chosen by whoever wrote the software).  Replay gain metrics are stored in the track’s metadata for use by players that support the function. This is done in the background and not during playback.  It does not alter the file’s audio content at all and is easily removed or reset if that track is placed into another set of tracks.

[bluesman]

2 hours ago, bluesman said:

I’m pretty sure that Fairlight (the audio editing part of DaVinci Resolve) is nondestructive and can edit during playback.

I just imported a simple FLAC file into DaVinci, and it works VERY well!  It will edit during playback and gives amazingly precise control over timing of edits (including gain changes).  You can export an edited copy of the original and preserve the source file unaltered.  Unfortunately, it will only decode FLACs - it does not encode FLAC exports (yet).  So we're limited to exporting edited FLACs as wavs and converting them back to FLACs using other software (an easy enough task).  Similarly, you can edit and export audio from videos.