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:

Subcommand	The gap it fills	What it does
baken headroom	Auto Gain is ignored on USB export	Measures LUFS / True Peak and bakes safe gain into the audio file — no limiter, dynamics preserved, cues stay linked
baken rbsort	No compound Key+BPM sort in Rekordbox	Sorts playlists by Camelot Key (1A→12B) then BPM and writes the order into collection.xml — CDJs play it in that exact order
baken cdjsafe	Pre-NXS2 CDJs only play MP3 reliably	Transcodes a whole playlist to 320 kbps CBR MP3 with cues and beatgrid carried over — the emergency-backup USB

🌐 baken.ravers.workers.dev — full docs, workflow guides, and FAQ.

Installation

baken requires ffmpeg. Package managers install it automatically.

Platform	Command
macOS (Homebrew)	brew install M-Igashi/tap/baken
Windows (winget)	winget install M-Igashi.baken
Arch Linux (AUR)	yay -S baken-bin
Cargo	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 <subcommand> --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

1. Scans the target directory for audio files (FLAC, AIFF, WAV, MP3, AAC/M4A)
2. Measures LUFS (Integrated Loudness) and True Peak using ffmpeg
3. 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
4. Displays categorized report
5. Two-stage confirmation:
   • First: "Apply lossless gain adjustment?" (lossless + native MP3/AAC)
   • Second: "Also process files with re-encoding?" (MP3/AAC requiring re-encode)
6. 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:

1. Scanning and analyzing all audio files
2. Reviewing the categorized report
3. Confirming lossless processing
4. Optionally enabling MP3/AAC re-encoding
5. 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 <target>/backup
• CSV report is written unless --no-report; --report PATH sets a custom location
• --analyze-only runs analysis + report only, skips processing

Run baken headroom --help for the full flag reference.

Processing Methods

baken selects the optimal method for each file based on format and headroom:

Format	Method	Precision	Quality Loss
FLAC, AIFF, WAV	ffmpeg	Arbitrary	None
MP3, AAC/M4A	mp3rgain (built-in)	1.5dB steps	None (global_gain modification)
MP3, AAC/M4A	ffmpeg re-encode	Arbitrary	Inaudible at ≥256kbps

Three-Tier Approach for Lossy Formats (MP3/AAC)

Each MP3 and AAC/M4A file is categorized into one of three tiers:

1. Native Lossless — ≥1.5 dB headroom to the configured ceiling

   • Truly lossless global_gain header modification in 1.5dB steps
   • Uses built-in mp3rgain library
   • Applied automatically (no user confirmation needed)

2. 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

3. 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:

1. 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.
2. 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.

See docs/true-peak-ceiling.md for a longer walk-through with citations.

Tuning the ceiling

Goal	Flag	Resulting ceiling
Default (max-aggressive delivery)	(none)	-0.5 dBTP for all files
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:

Target	Requires TP ≤
-0.5 dBTP (default)	-2.0 dBTP
-1.0 dBTP (--tp-target -1.0)	-2.5 dBTP
-2.0 dBTP (--tp-target -2.0)	-3.5 dBTP

Example: 320 kbps file at -3.5 dBTP, default target → 2 steps (+3.0 dB) → -0.5 dBTP (optimal).

Re-encode Quality

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

1. Set key display to Alphanumeric (1A..12B notation) in Rekordbox: Preferences > View > Key display format > Alphanumeric.
2. Export: File > Export Collection in xml format → e.g. ~/Music/rekordbox/collection.xml.
3. 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 <PATH> to override.
4. 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).
5. 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.
6. Verify the sort by clicking any playlist inside Sorted (Key+BPM)/ — tracks should run 1A (lowest BPM) → 1B → 2A → … → 12B (highest BPM).
7. Drag the playlists you want from Sorted (Key+BPM)/ into your main Playlists collection. Your original playlists (still in Playlists) are unchanged.
8. 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>	Path to collection.xml (required)
--playlist <PATH>	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 <PATH> (-o)	Output XML path. Optional — defaults to <input-stem>-out.<ext> next to the input
--name <NAME>	Override the sorted playlist's name. Only valid with --playlist. When sorting all playlists, each sorted copy reuses its source name

Sort Rules

• Primary: Camelot Key ascending — 1A → 1B → 2A → 2B → … → 12A → 12B
• Secondary: BPM ascending within each key group
• 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 <PLAYLISTS> ROOT NODE, regardless of how many playlists were processed. The ROOT Count is bumped by 1.

CDJ-safe Transcoder (baken cdjsafe)

Added in v3.0.0. Design discussion: #40.

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.

baken cdjsafe \
  --xml ~/Music/rekordbox/collection.xml \
  --playlist "Sets/Friday" \
  --out-dir ~/Music/cdjsafe-friday

What it does

1. Reads the target playlist from your exported collection.xml.

2. 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)

3. Emits an updated XML (default: <input>-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)/<playlist> folder. New entries get a [cdjsafe] marker appended to their Comments so they're distinguishable after import.

4. 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

1. Preferences > Advanced > Database > rekordbox xml > Imported Library → select the output XML, restart Rekordbox.
2. Open the rekordbox xml sidebar tree → CDJ-safe (MP3)/<playlist>.
3. Right-click the imported tracks → Import to Collection. Cues and beatgrid come with them — no re-analysis needed.
4. Export the playlist to USB in EXPORT mode as usual.

Flags

Flag	Description
--xml <PATH>	Path to collection.xml (required)
--playlist <PATH>	Playlist to convert (required). Top-level: just the name; nested: Folder/Playlist
--out-dir <DIR>	Directory for the MP3 files (required; created if missing)
--output <PATH> (-o)	Output XML path. Defaults to <input-stem>-out.<ext> 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).

License

MIT