LUFS Unifier GUI Version

A tool for unifying LUFS using linear gain adjustment only. This is the GUI version of LUFS Unifier. By selecting optional features, it can also function as the GUI version of LUFS Unifier Simple.

Development Background

When creating compilation albums or best-of collections from digital audio files gathered from various sources, volume differences between tracks inevitably become a problem. Inconsistent volume levels make listening frustrating and uncomfortable. This tool was developed to solve that problem.

The key feature of this tool is its design to preserve the "musical dynamics" that are often lost in typical normalization processes, maintaining them to the greatest extent possible.

Overview

Main Features

• Unifies LUFS using linear gain adjustment only, normalizing the perceived volume of input WAV, FLAC, and ALAC files, and saves them as WAV files.
• FLAC/ALAC files are automatically converted to WAV. Original sample rate and bit depth are preserved.
• All metadata from original files are preserved, including album artist, artist, album, disc number, track number, title, composer, year, genre, and cover art.

Optional Features

1. Remove silence from the beginning and end of each file.
2. Convert and save as ALAC files (Apple Lossless: lossless compression format) for use on smartphones and other devices.
3. High-quality conversion to CD format (44.1kHz/16-bit) WAV files.
4. Save processing logs from this tool.

System Requirements

OS

Windows 10 or later

Other

FFmpeg installation required. Easy installation using FFmpeg Manager.

Alternatively, place ffmpeg.exe in the same folder as lufs_unifier_gui.exe for automatic detection.

Distribution Files

lufs_unifier_gui.exe

EXE file

Download

lufs_unifier_gui.zip (24.7MB)

Supported Formats

WAV

Uncompressed audio files (supports all sample rates/bit depths)

FLAC

Free Lossless Audio Codec (lossless compressed audio files)

M4A (ALAC)

Apple Lossless Audio Codec (lossless compressed audio files)

How to Use

Selecting Audio Files and Execution

• Select files or folders using the Add Files or Add Folder buttons.
• You can also drag and drop multiple files/folders into the Input File area.
• Individual files, folders, or a mix of both can be dropped.
• Only WAV/FLAC/M4A files within folders will be processed (subfolders are excluded).
• Press the Start button to begin processing.

Processing Details

Main Processing

LUFS Unifier functionality - adjusting only linear gain to unify LUFS and saving as WAV - is always executed.

Optional Processing

The following processes can be added or skipped as options. Select using checkboxes.

1. Remove silence from beginning and end before LUFS unification
2. Convert and save WAV files after LUFS unification to ALAC format (Apple Lossless Audio Codec, lossless compression)
3. Convert and save WAV files after LUFS unification to CD format (44.1kHz/16-bit)
4. Save all processing logs as a text file

CD Format Conversion Method

Resampling

soxr HQ (high quality)

Dithering

TPDF triangular (for 16-bit conversion)

Processing Target

Automatically detects and converts only files not already in 44.1kHz/16-bit format

This conversion enables creation of high-quality CD production audio from high-resolution sources.

Output Folders

After processing, the following folders are created in the original WAV file folder, and respective files are saved:

Original WAV file folder
    |            └── *.wav (original WAV files)
    |── output_unified folder
    |    |       ├── *_unified.wav (WAV files after LUFS unification)
    |    |       └── *.txt (text files recording processing details)
    |    ├── alac folder
    |    |       └── *.m4a (converted ALAC files)
    |    └── output_cd44 folder
    |            └── *_unified_cd.wav (44.1kHz/16-bit WAV files)
    └── trimmed folder (temporary storage for silence-trimmed files, automatically deleted after processing)

• Tag information (artist name, album name, track title, jacket image, etc.) from original WAV files is completely preserved in processed WAV files and ALAC files.
• Before using this tool, it is recommended to properly enter tag information (ID3v2.3) for original WAV files using MP3TAG or similar tools.
• If all WAV files have the same "Album Name" tag information, the folder will be named after the album name instead of "alac".

Audio Terminology

RMS (Root Mean Square)

An indicator representing the average strength of sound, also known as effective value.

What it Measures

The "actual power" of sound

Characteristics

Relatively close to the volume perceived by the human ear

Unit

dB (decibels), e.g., -12 dB RMS

Applications

Volume balance adjustment during mixing

LUFS (Loudness Units relative to Full Scale)

A loudness unit and currently the most important volume measurement standard.

What it Measures

"Perceived loudness" actually felt by humans

Characteristics

Considers frequency characteristics, most closely matching human auditory perception

Unit

LUFS

Streaming Standards:

Spotify: -14 LUFS

YouTube: -14 LUFS

Apple Music: -16 LUFS

Applications

Mastering for streaming distribution

Measurement Method in This Tool

Using FFmpeg's ebur128 filter (ITU-R BS.1770-4 compliant)

TP (True Peak)

The true peak value representing the maximum possible volume that can occur during digital-to-analog conversion.

What it Measures

The actual maximum volume that can occur after DA conversion (digital-to-analog conversion)

Characteristics

Detects hidden peaks that cannot be detected by standard peak meters

Unit

dBTP (decibels True Peak)

Recommended Value

-1 dBTP or lower (to prevent clipping)

Applications

Final check during mastering

Measurement Method in This Tool

Using FFmpeg's ebur128 filter (ITU-R BS.1770-4 compliant), measuring simultaneously with LUFS for accelerated processing (approximately 1.5-2x faster)

LRA (Loudness Range)

Loudness Range represents the width of volume variation throughout a track.

What it Measures

The difference between quiet and loud parts in a song

Characteristics

Quantifies the dynamics (expressiveness) of music

Unit

LU (Loudness Units)

Guidelines

3-6 LU: Heavy compression (EDM, Pop)

10-15 LU: Moderate dynamics (Rock)

15+ LU: Rich dynamics (Classical, Jazz)

Detailed Operation of This Tool

While the basic goal is to unify LUFS, typical "normalization processing" to achieve a specific LUFS value is not performed. This is because normalization can significantly alter the dynamics (LRA) of music in some cases.

Therefore, this tool unifies LUFS using only linear gain adjustment. The processing flow is as follows:

1. Measure LUFS and TP for each file (ITU-R BS.1770-4 compliant)
2. By default, limit TP to -0.5 dB, calculate the difference between each file's TP and -0.5, and compute MAX LUFS for how much LUFS can be raised (or lowered) for each file
3. Consider the minimum value of MAX LUFS for all files as the Target LUFS for all files
4. Adjust gain for each file by the difference between its LUFS and Target LUFS
5. Re-analyze step 4, and if maximum TP is not at -0.5, adjust Target LUFS and perform gain adjustment again
6. By default, allow TP error of 0.01 dB to converge gain adjustment (maximum 10 iterative gain adjustments)
7. After processing completion, automatically delete intermediate files (trimmed folder)

This logic theoretically achieves zero LRA variation by unifying LUFS through linear gain adjustment only.

Audio Quality Improvement Features

The following audio quality improvement features are automatically applied during linear gain adjustment processing.

DC Component Removal

Automatically removes DC component (DC offset) for accurate peak measurement

Float64 High-Precision Calculation

Internal processing executed in 64-bit floating point to minimize cumulative calculation errors

Triangular Dithering

Reduces quantization noise for 16-bit output (automatically skipped for 24-bit or higher. Limiting is intentionally not implemented)

Memory Optimization

Memory optimization features are implemented for stable processing of large files

Dynamic Worker Adjustment

Automatically adjusts parallel processing thread count based on file size

File Size Determination

Small size (average <50MB): Full parallel processing as specified

Medium size (average 50-100MB): Parallel count reduced to 75%

Large size (average ≥100MB, maximum <200MB): Parallel count reduced to 50%

Very large size (maximum ≥200MB): Single-thread processing

On-Demand Processing

Audio data is not kept in memory but read from original files when needed

Settings

Processing

Target True Peak (dB) (Default: -0.5)

Target True Peak value. The True Peak of final WAV files will always be at or below this setting. Typically set to around -0.5dB to prevent clipping.

Max Iterations (Default: 10)

Maximum iteration count for LUFS adjustment. Usually once is sufficient, but default is set to 10 for safety margin. Generally no need to modify.

Max Workers (Default: 1/2 of CPU cores, minimum 4)

Maximum number of parallel worker threads. Adjusting according to PC's CPU core count can speed up processing. This becomes the maximum value for automatic adjustment based on file size.

TP Convergence (dB) (Default: 0.01)

True Peak (TP) convergence tolerance margin. Adjustment is considered complete when the difference between Target True Peak and adjusted WAV file's TP is within this setting.

Silence Trimming

Threshold (dB) (Default: -50.0)

Volume level below which audio is considered silence. -50dB is typical.

Min Duration (s) (Default: 0.05)

Minimum duration to be considered silence. Shorter silence periods are ignored.

Head Keep (s) (Default: 0.2)

Duration from the beginning that will not be removed. Protects fade-ins and similar effects.

Tail Keep (s) (Default: 1.0)

Duration from the end that will not be removed. Protects reverb and fade-outs.

Frame Length (s) (Default: 0.1)

Analysis frame length for silence detection. 0.1 seconds is typically sufficient.

FFmpeg Timeouts

Check Timeout (s) (Default: 10)

Timeout for FFmpeg existence verification. 10 seconds is usually sufficient.

True Peak Timeout (s) (Default: 30)

Timeout for True Peak measurement processing. Increase if failing with large files.

ALAC Timeout (s) (Default: 120)

Timeout for ALAC format conversion processing. Increase if failing with large files.

Disclaimer

• Use of this tool is at your own risk.
• The developer assumes no responsibility for any changes or loss of audio quality resulting from audio file processing.
• Backing up important files beforehand is strongly recommended.
• For commercial use, comply with relevant copyright laws and licensing agreements.
• The developer assumes no responsibility for any damages arising from the operation of this tool.
• Due to Windows specification changes or FFmpeg updates, the tool may cease to function in the future.
• Support is generally not provided.

Version History

January 2026 v3.0

Removed unused libraries to significantly reduce EXE file size (134MB→25MB) and improve startup time. Added tooltip (full path display) to file list. Changed CD conversion resampling to soxr HQ.

January 2026 v2.9

Released as GUI Version. Internalized yaml files, made settings adjustable in GUI. Made it possible to save and load original settings as yaml files.

Developer Information

Developer: Noriya

E-mail: noriyahd28v@gmail.com

This tool was developed to provide music enthusiasts with a better listening experience. If you have any questions or feedback, please feel free to contact us at the above address.