tokyo-wangan-racing/docs/ROTARY_SOUND.md

Status: loops are BUILT ✅ — awaiting Studio upload

Real 13B loops were extracted from the owner's own drive footage (/mnt/user/data/c-finished-videos/2026-07-10/, same car) and processed on the workstation. They live at:

• assets/audio/rx7_idle_loop.ogg — 15.9 s steady idle (~99 Hz fundamental, scanned as the most tonally stable stretch of the session; seam jump 0.001)
• assets/audio/rx7_rev_loop.ogg — 7.4 s held higher-RPM pull (~105 Hz, louder section; seam jump 0.005)
• Masters (.wav + .ogg) mirrored to the NAS: .../001-1993 Mazda RX-7/sound/

Remaining (owner, in Studio): upload the two .ogg files (Asset Manager → Import, or Creator Dashboard → Audio), wait for moderation, then paste the two asset IDs into CAR_SOUNDS.rx7_fc in src/client/SoundController.luau.

If a longer/angrier rev is wanted later, more source material exists in the other sessions under c-finished-videos/ — the extraction is repeatable (method below).

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Pipeline reference (how the loops were made / how to redo them)

The RX-7 must sound like a rotary. The pipeline: the owner's own recordings → processed into two seamless loops on this workstation → uploaded in Studio → IDs pasted into SoundController.CAR_SOUNDS.

What the game needs (two loops)

Loop	Content	Length
Idle	Engine idling, steady. The rotary lope/brap at rest.	5–10 s
Rev	Held at steady mid-high RPM (~4–6k), NOT a sweep.	5–10 s

Steady-state matters: the game pitch-shifts and crossfades these, so a loop recorded during rising RPM will "wander" audibly. A long recording containing steady sections is fine — the good seconds get cut out in processing.

Step 1 — Record (or use existing video)

Any source works: phone video, GoPro footage, a Zoom H5 recording. Existing videos of the car are fine — audio gets extracted. Best results:

• Record OUTSIDE the car, mic a few feet from the exhaust.
• Get ≥10 s of steady idle and ≥5 s of held revs.
• Avoid wind over the mic and people talking.

Drop the files on the NAS next to the reference photos:

unraid-1:/mnt/user/data/yy-roblox-games/0-fast-n-furious-sim/001-1993 Mazda RX-7/sound/

Step 2 — Process into seamless loops (this workstation)

Hermes does this — the box already has ffmpeg + numpy/scipy (avsync-research venv). Ask and it happens; for reference the recipe is:

1. Extract audio: ffmpeg -i clip.mp4 -vn -ac 1 -ar 48000 raw.wav
2. Find a steady window (visually via spectrogram, or scripted RMS/pitch scan).
3. Cut the loop at zero-crossings and apply a short equal-power crossfade from the tail onto the head so the seam is inaudible: loop-body + (last ~150 ms faded out, overlaid on first ~150 ms faded in).
4. Normalize to about -3 dBFS peak, export .ogg (smaller upload, Roblox-native): ffmpeg -i loop.wav -c:a libvorbis -q:a 6 rx7_idle_loop.ogg
5. Verify: play the file on repeat (ffplay -loop 0) — no click, no wander.

Outputs: rx7_idle_loop.ogg + rx7_rev_loop.ogg, copied back to the NAS sound/ folder and kept in assets/audio/ locally (small enough to commit).

Step 3 — Upload in Studio (owner)

1. Studio → View → Asset Manager → Import (or the Creator Dashboard → Development Items → Audio) → upload both .ogg files.
2. Audio uploads require an ID/phone-verified account; private audio uploaded to YOUR account is playable in YOUR experiences — exactly our case.
3. Copy each asset ID after moderation clears (usually minutes).

Step 4 — Wire in

In src/client/SoundController.luau, uncomment and fill:

local CAR_SOUNDS: { [string]: EngineSounds } = {
	rx7_fc = {
		Idle = "rbxassetid://<idle id>",
		Rev = "rbxassetid://<rev id>",
	},
}

Rebuild, playtest, adjust IDLE_PITCH_* / REV_PITCH_* / CROSSFADE_* to taste. Done — the RX-7 braps.

Why not a toolbox rotary?

Searched; candidates exist (e.g. "13B ROTARY ENGINE SOUND", id 118059219867199) but can't be auditioned outside Roblox (asset downloads require auth), most are short unloopable rips, and rights are murky. The owner HAS the real car — its actual engine is strictly better than any stranger's rip. Toolbox is the fallback only if recording proves impractical: audition in Studio before committing to one.