headroom is an audio analysis tool designed to measure loudness (LUFS) and headroom in audio files, then apply precise gain adjustments to maximize loudness while preserving dynamics. It supports a wide range of file formats, including MP3, AAC/M4A, FLAC, AIFF, and WAV.
Key Features:
Lossless gain adjustment for MP3 and AAC files using the built-in mp3rgain library.
Batch processing capability for efficient workflow.
Metadata preservation to maintain Rekordbox tags, cue points, and other embedded data.
Smart True Peak ceiling targeting based on AES TD1008 recommendations.
Guided command-line interface with two-stage confirmation for safe processing.
Ideal for DJs, producers, and mastering engineers looking to normalize track levels without compromising audio quality. headroom ensures consistent playback volume across tracks while maintaining dynamic integrity. It can be installed via winget for Windows users.
README
Bake'n Deck (baken)
What you prep in Rekordbox is what plays on the deck.
Rekordbox does three things in software that never survive the trip to a CDJ. Bake'n Deck bakes each one into the files themselves:
cargo install baken (ffmpeg must be installed separately)
Pre-built binaries are available on the Releases page (ffmpeg must be installed separately). To build from source: git clone https://github.com/M-Igashi/baken.git && cd baken && cargo build --release.
Quick Start
baken headroom ~/Music/DJ-Tracks # analyze & bake loudness gain (interactive)
baken rbsort --xml collection.xml # sort every playlist by Key+BPM
baken cdjsafe --xml collection.xml --playlist "Sets/Friday" --out-dir ~/Music/cdjsafe
Run baken --help or baken --help for the full reference.
> [!NOTE]
> Renamed from headroom at v3.0.0 (#60). The old headroom install channels (brew/winget/cargo/AUR) no longer receive updates — reinstall via the baken packages above. The loudness analyzer now lives under the baken headroom subcommand.
Highlights
Single binary — mp3rgain built in; only ffmpeg required (and rbsort doesn't even need that)
Truly lossless MP3/AAC gain — global_gain header modification in 1.5 dB steps, no re-encode
Uniform True Peak ceiling — -0.5 dBTP by default (AES TD1008 §7B), tunable via --tp-target
Non-destructive — automatic backups; rbsort/cdjsafe never modify your original collection.xml
Metadata preserved — files overwritten in place, so Rekordbox cues, hot cues, and beatgrids stay linked
Interactive or scriptable — guided two-stage confirmation, or flags/globs for pipelines and CI
Loudness Normalizer (baken headroom)
How It Works
Scans the target directory for audio files (FLAC, AIFF, WAV, MP3, AAC/M4A)
Measures LUFS (Integrated Loudness) and True Peak using ffmpeg
Categorizes files by processing method:
Green: Lossless files (ffmpeg)
Yellow: MP3/AAC files with enough headroom for native lossless gain
Magenta: MP3/AAC files requiring re-encode
Displays categorized report
Two-stage confirmation:
First: "Apply lossless gain adjustment?" (lossless + native MP3/AAC)
Second: "Also process files with re-encoding?" (MP3/AAC requiring re-encode)
Creates backups and processes files
Example
Full interactive session (28 files analyzed → 10 processed)
$ cd ~/Music/DJ-Tracks
$ baken headroom
╭─────────────────────────────────────╮
│ baken v3.0.1 │
│ Bake'n Deck — CDJ Prep Toolkit │
╰─────────────────────────────────────╯
▸ Target directory: /Users/xxx/Music/DJ-Tracks
✓ Found 28 audio files
✓ Analyzed 28 files
● 3 lossless files (ffmpeg, precise gain)
Filename LUFS True Peak Target Gain
track01.flac -13.3 -3.2 dBTP -0.5 dBTP +2.7 dB
track02.aif -14.1 -4.5 dBTP -0.5 dBTP +4.0 dB
track03.wav -12.5 -2.8 dBTP -0.5 dBTP +2.3 dB
● 2 MP3 files (native lossless, 1.5 dB steps, requires TP ≤ -2.0 dBTP)
Filename LUFS True Peak Target Gain
track04.mp3 -14.0 -5.5 dBTP -0.5 dBTP +4.5 dB
track05.mp3 -13.5 -6.0 dBTP -0.5 dBTP +4.5 dB
● 2 AAC/M4A files (native lossless, 1.5 dB steps, requires TP ≤ -2.0 dBTP)
Filename LUFS True Peak Target Gain
track08.m4a -13.0 -4.0 dBTP -0.5 dBTP +3.0 dB
track09.m4a -12.5 -4.5 dBTP -0.5 dBTP +3.0 dB
● 2 MP3 files (re-encode required for precise gain)
Filename LUFS True Peak Target Gain
track06.mp3 -12.0 -1.5 dBTP -0.5 dBTP +1.0 dB
track07.mp3 -11.5 -1.2 dBTP -0.5 dBTP +0.7 dB
● 1 AAC/M4A files (re-encode required)
Filename LUFS True Peak Target Gain
track10.m4a -12.5 -1.8 dBTP -0.5 dBTP +1.3 dB
▸ TP target: -0.5 dBTP (uniform delivery ceiling, AES TD1008 §7B)
✓ Report saved: ./baken_report_20250109_123456.csv
? Apply lossless gain adjustment to 3 lossless + 2 MP3 (lossless gain) + 2 AAC/M4A (lossless gain) files? [y/N] y
ℹ 2 MP3 + 1 AAC/M4A files have headroom but require re-encoding for precise gain.
• Re-encoding causes minor quality loss (inaudible at 256kbps+)
• Original bitrate will be preserved
? Also process these files with re-encoding? [y/N] y
? Create backup before processing? [Y/n] y
✓ Backup directory: ./backup
✓ Done! 10 files processed.
• 3 lossless files (ffmpeg)
• 2 MP3 files (native, lossless)
• 2 AAC/M4A files (native, lossless)
• 2 MP3 files (re-encoded)
• 1 AAC/M4A files (re-encoded)
Usage
Interactive Mode
Run baken headroom without further arguments to use the guided workflow in the current directory:
cd ~/Music/DJ-Tracks
baken headroom
The tool will guide you through:
Scanning and analyzing all audio files
Reviewing the categorized report
Confirming lossless processing
Optionally enabling MP3/AAC re-encoding
Creating backups (recommended)
Scriptable Mode
Pass paths, globs, or flags to run non-interactively (useful for pipelines and scripts):
# Analyze a directory without modifying anything
baken headroom --analyze-only ~/Music/DJ-Tracks
# Apply only lossless gain, with backup, save report to a specific path
baken headroom --lossless --backup ./bak --report results.csv ./album/
# Enable re-encoding as well
baken headroom --lossless --reencode --backup ./bak ./album/
# Operate on specific files
baken headroom --lossless track1.mp3 track2.flac
# Glob patterns
baken headroom --lossless --no-report "./music/**/*.mp3"
# Tighter ceiling for streaming-platform delivery (Spotify / Apple / YouTube max)
baken headroom --lossless --tp-target -1.0 ./album/
# Restore the legacy bitrate-dependent split (pre-v1.10 behaviour)
baken headroom --lossless --tp-split-bitrate ./album/
Non-interactive defaults (when any flag or path is provided):
--lossless is on unless --no-lossless
--reencode is off unless --reencode is explicitly passed
--backup is off unless provided; bare --backup uses /backup
CSV report is written unless --no-report; --report PATH sets a custom location
Applied automatically (no user confirmation needed)
Re-encode — headroom exists but <1.5 dB to ceiling
Uses ffmpeg for arbitrary precision gain
MP3: libmp3lame with -q:a 0 / AAC: libfdk_aac (falls back to built-in aac)
Preserves original bitrate; requires explicit user confirmation
Skip — no headroom available
True Peak Ceiling
Default — uniform delivery target
Every file targets -0.5 dBTP by default. This is the maximum-aggression value that AES TD1008 §7B describes for high-rate codec inputs ("may work satisfactorily with as little as -0.5 dBTP for the limiting threshold").
File class
Ceiling
Native lossless requires
Lossless (FLAC, AIFF, WAV)
-0.5 dBTP
—
MP3 (any bitrate)
-0.5 dBTP
TP ≤ -2.0 dBTP
AAC/M4A (any bitrate)
-0.5 dBTP
TP ≤ -2.0 dBTP
Why a single ceiling — pre-encode vs delivery
TD1008 has two related but distinct numbers:
Generic delivery recommendation (§4) — "Maximum True Peak level not exceed -1 dBTP at the codec input of lossy-encoded streams." This is the pre-encode limiter threshold.
High-rate codec relaxation (§7B) — "High-rate (e.g., 256 kbps) coders may work satisfactorily with as little as -0.5 dBTP" — also a codec-input threshold; "the limiting threshold may need to be reduced below the recommended -1.0 dBTP" for lower bit rates.
Both bullets describe the limiter that sits in front of the encoder. baken operates in the opposite position: on already-encoded delivery files. There is no further codec stage downstream to absorb additional overshoot, so the bitrate-dependent slack TD1008 grants the pre-encode limiter does not transfer to the end product. A single, codec-agnostic delivery ceiling is the correct interpretation. -0.5 dBTP is chosen because it is the most aggressive value TD1008 sanctions for any limiter in the chain; lossless and high-rate lossy files were already at -0.5, and low-rate files now stop giving up an unnecessary 0.5 dB of loudness.
Match Spotify / Apple Music / YouTube delivery max
--tp-target -1.0
-1.0 dBTP for all files
Conservative master with extra player headroom
--tp-target -2.0
-2.0 dBTP for all files
Mirror TD1008's pre-encode interpretation
--tp-split-bitrate
-0.5 dBTP ≥256 kbps, -1.0 dBTP <256 kbps
--tp-target and --tp-split-bitrate are mutually exclusive. --tp-split-bitrate reproduces the pre-1.10 default exactly.
The native-lossless threshold scales with the chosen ceiling: it is always target − 1.5 dB (e.g. -0.5 → TP ≤ -2.0; -1.0 → TP ≤ -2.5; -2.0 → TP ≤ -3.5).
Output
CSV Report
Filename
Format
Bitrate (kbps)
LUFS
True Peak (dBTP)
Target (dBTP)
Headroom (dB)
Method
Effective Gain (dB)
track01.flac
Lossless
-
-13.3
-3.2
-0.5
+2.7
ffmpeg
+2.7
track04.mp3
MP3
320
-14.0
-5.5
-0.5
+5.0
mp3rgain
+4.5
track06.mp3
MP3
320
-12.0
-1.5
-0.5
+1.0
re-encode
+1.0
track08.m4a
AAC
256
-13.0
-4.0
-0.5
+3.5
native
+3.0
track10.m4a
AAC
256
-12.5
-1.8
-0.5
+0.7
re-encode
+0.7
Backup Structure
./
├── track01.flac ← Modified
├── track04.mp3 ← Modified
├── track08.m4a ← Modified
├── subfolder/
│ └── track06.mp3 ← Modified
└── backup/ ← Created by baken
├── track01.flac ← Original
├── track04.mp3 ← Original
├── track08.m4a ← Original
└── subfolder/
└── track06.mp3 ← Original
Notes & Technical Details
Files are overwritten in place after backup — Rekordbox metadata remains linked
Only files with positive effective gain are shown and processed
MP3/AAC native lossless requires at least 1.5dB headroom to be processed
MP3/AAC re-encoding is opt-in and requires explicit confirmation
macOS resource fork files (._*) are automatically ignored
Why 1.5dB Steps?
Both MP3 and AAC store a "global_gain" value as an integer. Each ±1 increment changes the gain by 2^(1/4) = ±1.5 dB. This is a format-level constraint, not a tool limitation.
baken uses the built-in mp3rgain library to directly modify this field — no decoding or re-encoding involved.
Native Lossless Threshold
Since native lossless gain only works in 1.5 dB steps, at least 1.5 dB of headroom to the configured target ceiling is required. The threshold scales automatically:
At ≥256kbps, re-encoding introduces quantization noise below -90dB — far below audible threshold. Only gain is applied (no EQ, compression, or dynamics processing), and original bitrate is preserved.
Rekordbox Playlist Sorter (baken rbsort)
Rekordbox does not expose a "sort by Key AND BPM" option in its UI. baken rbsort reads your collection.xml, sorts each target playlist by Camelot Key (1A → 12B) ascending then BPM ascending, and emits the sorted copies into a new Sorted (Key+BPM)/ folder appended to the same XML. Originals are left untouched. The layout mirrors the analyzer's backup/ directory: one container folder, each item inside keeps its source name.
This is the same idea as baken headroom applied to playlist order: Rekordbox's software-only features (Auto Gain, multi-column sort) don't follow your tracks to the CDJ. rbsort bakes Key+BPM order into the playlist itself — so when you export to USB in Rekordbox's EXPORT mode, the CDJ plays the set in that exact order with no on-deck reordering.
Workflow
Set key display to Alphanumeric (1A..12B notation) in Rekordbox: Preferences > View > Key display format > Alphanumeric.
Export: File > Export Collection in xml format → e.g. ~/Music/rekordbox/collection.xml.
Run rbsort:
# Sort every TrackID-referenced playlist in the XML
baken rbsort --xml ~/Music/rekordbox/collection.xml
# Or target one playlist (top-level: just the name)
baken rbsort \
--xml ~/Music/rekordbox/collection.xml \
--playlist "Happy House and Trance"
# Or target one nested under a folder
baken rbsort \
--xml ~/Music/rekordbox/collection.xml \
--playlist "Sets/Friday"
Output defaults to collection-out.xml next to the input. Pass --output to override.
Point Rekordbox at the output XML: Preferences > Advanced > Database > rekordbox xml > Imported Library → select collection-out.xml, then restart Rekordbox (Rekordbox only re-reads the XML on startup).
Open the rekordbox xml tree in the left sidebar. It is a separate tree from your main library — switch to it from the sidebar icon column on the far left (the icon labeled rekordbox xml). Inside you'll find a new folder Sorted (Key+BPM)/ containing each sorted playlist under its original name.
Verify the sort by clicking any playlist inside Sorted (Key+BPM)/ — tracks should run 1A (lowest BPM) → 1B → 2A → … → 12B (highest BPM).
Drag the playlists you want from Sorted (Key+BPM)/ into your main Playlists collection. Your original playlists (still in Playlists) are unchanged.
Export to USB for CDJ: switch Rekordbox to EXPORT mode (top-left dropdown), plug in your USB / SD, then right-click the playlist → Export Playlist. CDJs read tracks in playlist order by default — your Key+BPM sort plays back on the deck in that exact order.
> The sorted results live only inside the rekordbox xml > Sorted (Key+BPM)/ folder, not in your main Playlists. If you only see the originals, you're looking at the local library — switch sidebar trees.
Flags
Flag
Description
--xml
Path to collection.xml (required)
--playlist
Source playlist under the Rekordbox Playlists root. Optional — if omitted, every TrackID-referenced playlist in the XML is sorted. Top-level playlists: just the name (e.g. "Happy House and Trance"). Nested: /-separate folder/playlist names (e.g. "Folder/SubFolder/MyPlaylist")
--output (-o)
Output XML path. Optional — defaults to -out. next to the input
--name
Override the sorted playlist's name. Only valid with --playlist. When sorting all playlists, each sorted copy reuses its source name
Tracks with no Camelot key sort after all known keys; within a key group, tracks with BPM 0 / unanalyzed sort last
See docs/rbsort-sort-comparison.md for a 6-track walk-through showing how this compound sort differs from Rekordbox / CDJ's single-column Sort by Key and Sort by BPM.
Notes
Requires the Tonality field to be exported as 1A..12B (Rekordbox's "Alphanumeric" key display format). Non-matching values (e.g. Am, C#) are silently sorted last.
Only KeyType="0" (TrackID-referenced) playlists are supported. In all-playlists mode, non-KeyType=0 playlists are silently skipped; for a single target, rbsort errors out.
baken rbsort does not require ffmpeg — only the headroom and cdjsafe subcommands do.
A single Sorted (Key+BPM)/ folder is appended inside the `` ROOT NODE, regardless of how many playlists were processed. The ROOT Count is bumped by 1.
Pre-NXS2 CDJs (CDJ-2000NXS, CDJ-2000, CDJ-900NXS, CDJ-850, …) have inconsistent or absent support for anything that isn't MP3: FLAC needs an NXS2 (2016+), and ALAC/AIFF/WAV/AAC fail on specific firmware combinations — sometimes mid-set. baken cdjsafe is the emergency-backup path: it takes a gig playlist and produces a USB-ready set of files that will play on any CDJ, with your cues and beatgrid intact.
Reads the target playlist from your exported collection.xml.
Converts every track to the CDJ-safe profile — 320 kbps CBR MP3 @ 44.1 kHz, ID3v2.3 tags, artwork kept (JPEG, capped at 500×500):
Source
Action
FLAC, WAV, AIFF, ALAC
Re-encode
AAC/M4A (any bitrate)
Re-encode
MP3 not exactly 320 kbps CBR @ 44.1 kHz
Re-encode (lossy→lossy, reported)
MP3 already 320 kbps CBR @ 44.1 kHz
Byte-identical copy (no generation loss, LAME header untouched)
Emits an updated XML (default: -out.xml) where each converted track is a new entry with a fresh TrackID that inherits the source's beatgrid (TEMPO) and hot/memory cues (POSITION_MARK) verbatim, grouped in a CDJ-safe (MP3)/ folder. New entries get a [cdjsafe] marker appended to their Comments so they're distinguishable after import.
Reports every lossy→lossy re-encode so you can refresh those tracks from lossless masters before the next gig.
If any track fails to convert, no XML is written — a partial USB defeats the point.
Importing back into Rekordbox
Preferences > Advanced > Database > rekordbox xml > Imported Library → select the output XML, restart Rekordbox.
Open the rekordbox xml sidebar tree → CDJ-safe (MP3)/.
Right-click the imported tracks → Import to Collection. Cues and beatgrid come with them — no re-analysis needed.
Export the playlist to USB in EXPORT mode as usual.
Flags
Flag
Description
--xml
Path to collection.xml (required)
--playlist
Playlist to convert (required). Top-level: just the name; nested: Folder/Playlist
--out-dir
Directory for the MP3 files (required; created if missing)
--output (-o)
Output XML path. Defaults to -out. next to the input
Notes
The output profile is locked (320 kbps CBR / 44.1 kHz / ID3v2.3) — it's the only combination that plays reliably across the whole CDJ fleet, and CBR sidesteps Rekordbox's VBR cue-offset problem.
ffmpeg writes a valid Xing/LAME header, so Rekordbox compensates the LAME encoder delay and cues stay sample-aligned.
Filenames are FAT32/exFAT-sanitized; collisions get a numeric suffix.
Requires ffmpeg (with libmp3lame; soxr resampling is used when available).
