PARALIAKI RACING — ENGINE RECORDINGS

These are edited recordings of real engines. They are not all exact recordings
of the represented car. sources.json records every source, trim, estimated RPM,
license URL, download URL, transformation and SHA-256 checksum.

MINI COOPER S CABRIO
Running engine: TheLittleCrow, 2019 Mini Cooper S contact recordings (engine
block + chassis), Freesound 669618 and 669622. CC0 1.0.
https://freesound.org/people/TheLittleCrow/sounds/669618/
https://freesound.org/people/TheLittleCrow/sounds/669622/
Startup: sound_catcher99, Fiat Punto Grande gasoline start, Freesound 425158.
CC0 1.0. This starter is a petrol four-cylinder SUBSTITUTE, not a MINI recording.
https://freesound.org/people/sound_catcher99/sounds/425158/

BMW Z4 M40i
Pole Position Production, BMW M4 2014 exterior start/idle/blips/steady neutral
RPM, from Sonniss GameAudioGDC 2020. BMW S55 turbo inline-six SUBSTITUTE for
Z4 B58; exhaust and engine details differ. Not a model-exact Z4 recording.
https://sonniss.com/gameaudiogdc/

SKODA OCTAVIA TAXI
Startup + idle: Loffy, car_inside_start_idle_diesel_engine.wav, 2007 VW Passat,
Freesound 89948. Licensed CC BY 3.0; attribution to Loffy is required.
https://freesound.org/people/Loffy/sounds/89948/
https://creativecommons.org/licenses/by/3.0/
Changes: cropped start and idle, mono 44.1 kHz conversion, high-pass filtering,
level matching, pitch stabilization and loop seam overlap on the idle only.
Running loops: Soundholder, Audi A3 8L 1.9 TDI 2000 RPM and Volkswagen
Caravelle T5 2.0 TDI 3000 RPM, Sonniss GameAudioGDC 2020.
These are diesel SUBSTITUTES, not an exact Octavia recording.

LICENSES
CC0 1.0: https://creativecommons.org/publicdomain/zero/1.0/
CC BY 3.0: https://creativecommons.org/licenses/by/3.0/
Sonniss GameAudioGDC license v2.0, effective 27 August 2026:
https://sonniss.com/gdc-bundle-license/
Sonniss material is licensed for use inside this game. Do not redistribute it
as a sound library, asset pack or project template. The finished game may be
shared/published; collaborators may use these assets to work on this game.
These files are not covered by any general source-code license of the project.

IMPLEMENTATION AND LIMITATIONS
The public Freesound HQ MP3 previews were used, not the account-gated original
WAVs. Sonniss sources are original 96 kHz WAVs. Runtime files are PCM16 mono
44.1 kHz WAV: no decoder padding at seams, and no external audio requests.
RPM references are harmonic-analysis estimates, except the producer-labelled
TDI loops. Short sections of revs were pitch-stabilized, seams overlapped, DC
removed and levels matched. The high MINI loop is short (0.43 s); a longer
steady full-load recording would improve variation. Load uses filtering and
gain, not separate measured load/coast recordings. World sounds have their own
credits; turbo/shift effects are procedural. Rivals and catalogue traffic select their own profile and sample bank. Engine synthesis remains as a decode fallback.

ADDITIONAL SYNTHESIZED ENGINES
Porsche 991.1 Carrera 3.4: flat6, six-cylinder pulse model, 7,800 RPM redline.
Toyota GR Yaris 1.6: turbo3, three-cylinder pulse model, 7,200 RPM redline.
Alfa Romeo 2000 GTV: na4, four-cylinder twin-cam character, 6,500 RPM redline.
These are procedural approximations, not recordings of the named cars. Each
has four RPM bands with load/coast layers. The Yaris uses turbo spool/lift-off
effects; Carrera and GTV do not. No recorded startups are assigned to these cars.

Audition all six: /tools/audio-preview.html (served from the project root).
Rebuild: python tools/build_engine_audio.py --cache /path/to/source-cache
For just the MINI mid layer, append --only mini-mid.wav. Its current trim is
76–78 seconds of the same CC0 Cooper S recording, with the existing pitch
stabilization and loop crossfade. This replaces a more uneven 29–32 second
section; the original edited WAV is preserved as mini-mid.wav.orig and its
trim/checksum are in sources.json (previousVersion). No EQ or envelope
normalization was applied. The idle and other RPM layers are unchanged.
Requires ffmpeg, numpy and scipy. Masters are cached outside runtime assets.
To upgrade fidelity further, replace substitute sources with separately
licensed Z4 B58 / Octavia EA288 / MINI B48 ignition recordings, plus sustained
on-load and off-load dyno RPM takes. Do not use game-ripped mod audio as masters.

Sound v2 runtime playback: MINI layers and other takes shorter than 1.25 seconds
use a cached 24-second granular bed. Random source offsets and +/-40% onset
jitter retain varied texture. Sine equal-power windows overlap by at least 60%.
The recorded firing body is phase-aligned and divided by the window sum;
decorrelated texture is divided by the square root of summed window powers.
Each summed band receives smooth look-ahead RMS normalization. Circular
overlap-add keeps the long-bed wrap continuous. Audio-rate pitch follows RPM
and Doppler. No source audio asset or licence changed.

VEHICLE AUDIO MODULE REFACTOR (2026-10-15)
No source recording or audio asset changed. src/audio/engine-profiles.js maps
additional turbo I4 trims to the existing CC0 MINI takes and turbo I6 trims to
the existing Sonniss BMW M4 substitute; diesel I4/van trims use the attributed
Loffy + Sonniss diesel takes above. City I4s use the MINI recording as a quiet,
filtered four-cylinder substitute, not a model-exact naturally aspirated take.
No suitable licensed flat-six, NA I6, V6/V8 biturbo or V10 takes are in this
repository: these remain explicitly procedural firing-order approximations.
Bus I6, motorcycles and NA I3 also have distinct procedural fallback profiles.
Starter fallback, shutdown, shift lever, clutch, paddle and pass-by effects are
original procedural synthesis; no new third-party effect samples were added.
See src/audio/README.md for every car/trim and .scratch/engine-audio/README.md
for game-mix demonstration captures. These are review evidence, not a sound
library or a grant to redistribute the underlying Sonniss recordings.

External bus and motorcycle profiles retain the existing world pack recordings
when decoded: CC0 bus idle by bikesnbassboi, scooter idle by lovretta, scooter
running by dif1891 (assets/audio/world/CREDITS.txt). Bus running uses the
existing Sonniss TDI substitute; synthesis is the missing/decode fallback.