Flacgain !!exclusive!!

: It is frequently used in scripts, such as tag_collection.sh , to batch process entire music libraries organized by album directories. Common Usage Contexts

: It scans FLAC files to determine their perceived loudness and adds "album gain" or "track gain" tags. flacgain

The MP3gain and ReplayGain standards successfully addressed the problem of perceived loudness normalization for lossy codecs (MP3, AAC, Ogg Vorbis) and lossless playback. However, these systems operate on a single global gain value per track or album, linearly scaling the entire waveform. This paper introduces , a novel extension to the FLAC (Free Lossless Audio Codec) ecosystem that goes beyond global loudness normalization. FLACgain analyzes a lossless stream to generate a perceptual dynamic range profile and encodes it as a reversible metadata sidechain. This allows a decoder or player to dynamically adjust gain on a short-term basis (e.g., per 50ms window) to achieve a consistent perceptual loudness envelope without crushing transient peaks or raising noise floors unnaturally. The result is an archive that retains perfect bit-identical reconstruction while offering an enhanced listening experience—especially for classical music, jazz, and film scores with extreme dynamics. : It is frequently used in scripts, such as tag_collection

Code and dataset under MIT license.