Subchapter 27.55

Bgm

scripts/11 files

scripts/lib/13 files

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Bgm

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Source

audio/scripts/lib/bgm.mjs

JavaScript253 lines11 KB

1// bgm.mjs — background music for the media audio engine. Two routes, gated the
2// same way as TTS/SFX:
3//
4//   retrieve (default when HeyGen is configured) — search HeyGen's music library
5//        by mood, download the top track. Synchronous. assets/bgm/track.mp3.
6//   generate (the alternative; the automatic choice when HeyGen is absent) —
7//        Lyria (cloud, $GEMINI_API_KEY/$GOOGLE_API_KEY + google-genai) preferred,
8//        else local MusicGen (facebook/musicgen-small via transformers). Spawned
9//        DETACHED so the engine can return while audio renders; the caller marks
10//        bgm_pending and runs wait-bgm.mjs before assembling. assets/bgm/track.wav.
11//
12// Missing/failed BGM never blocks a render.
13
14import

bgm.mjs on GitHub

{ spawn, spawnSync }

from

"node:child_process"

;

import { existsSync, mkdirSync, openSync, closeSync } from "node:fs";

import { join } from "node:path";

import { downloadTo, searchSounds } from "./heygen.mjs";

import { pythonInvocation } from "./python.mjs";

const r3 = (x) => Number(x.toFixed(3));

const lyriaKey = () => process.env.GEMINI_API_KEY || process.env.GOOGLE_API_KEY || "";

import { bgmDefaultVolume } from "./bgm-volume.mjs";

export { BGM_BED_VOLUME, BGM_SILENT_VOLUME, bgmDefaultVolume } from "./bgm-volume.mjs";

const BGM_PY_DEPS = ["transformers", "torch", "soundfile", "numpy"];

const BGM_PY_PROBE =

"import transformers, soundfile, torch, numpy; from transformers import MusicgenForConditionalGeneration";

const LYRIA_PY_DEPS = ["google-genai", "python-dotenv"];

const LYRIA_PY_PROBE = "import google.genai";

function pyOk(probe) {

const { cmd, args } = pythonInvocation(["-c", probe]);

return spawnSync(cmd, args, { stdio: "ignore" }).status === 0;

}

// `python -m pip`, not a bare `pip` binary: a Homebrew/system Python often

// exposes only `python3`/`pip3` on PATH, so a plain `pip` spawn silently

// no-ops (ENOENT) and the documented "auto-installed on demand" path never

// actually installs. `-m pip` also guarantees the packages land in the SAME

// interpreter pyOk() probes — a bare `pip`/`pip3` could resolve to a

// different Python installation than `python3` if more than one is on PATH.

function pipInstall(deps) {

const { cmd, args } = pythonInvocation(["-m", "pip", "install", "-q", ...deps]);

return spawnSync(cmd, args, { stdio: "ignore" }).status === 0;

}

// ── retrieval (HeyGen music library) ──────────────────────────────────────────

export async function retrieveBgm({ query, headers, hyperframesDir, hasVoice }) {

const q = query || "calm cinematic underscore";

const results = await searchSounds(q, "music", headers, { limit: 5 });

if (!results.length) return null;

const top = results[0];

const rel = "assets/bgm/track.mp3";

await downloadTo(top.audio_url, join(hyperframesDir, rel));

return {

path: rel,

volume: bgmDefaultVolume(hasVoice),

query: q,

mode: "retrieve",

duration_s: typeof top.duration === "number" ? r3(top.duration) : null,

};

}

// ── mood inference (for the generate path's prompt) ──────────────────────────

// Industry base → archetype shape → emotional-arc tiebreaker. Exported so a

// workflow adapter can build a rich prompt from its own narrative metadata; the

// engine also calls it when generate has only a plain mood query.

export function inferBgmPrompt({ blob = "", archetype = "", arc = "", userPrompt = "" } = {}) {

if (userPrompt) return userPrompt;

const b = String(blob).toLowerCase();

let base;

let bpm;

if (/\b(crypto|nft|web3|defi|token|blockchain|exchange|wallet|dao)\b/.test(b)) {

base = "atmospheric electronic, deep bass, futuristic synths, restrained percussion";

bpm = 100;

} else if (/\b(finance|fintech|bank|payment|invest|wealth|insurance|treasury)\b/.test(b)) {

base = "calm cinematic, soft strings, subtle piano, restrained percussion";

bpm = 92;

} else if (/\b(creative|agency|design|studio|art|brand|marketing|content)\b/.test(b)) {

base = "playful electronic, warm pads, light percussion";

bpm = 115;

} else {

base = "uplifting corporate tech, bright modern piano with synth pads";

bpm = 108;

}

const at = String(archetype).toLowerCase();

const ar = String(arc).toLowerCase();

if (/\bpas\b|pain.agitate|pain.+solve/.test(at))

return `${base}, starts with subtle tension then builds to resolution, BPM ${bpm}, transitions from MINOR to MAJOR`;

if (/\bbab\b|before.after|future.pac|vision/.test(at))

return `${base}, cinematic and aspirational, steady build with rising energy, BPM ${bpm}, MAJOR`;

if (/cascade|feature.benefit/.test(at))

return `${base}, energetic and driving, consistent momentum, BPM ${Math.min(bpm + 10, 128)}, MAJOR`;

if (/demo.loop|question.+answer/.test(at))

return `${base}, clean and focused, minimal arrangement, BPM ${Math.max(bpm - 8, 88)}`;

return `${base}, builds from understated tension to uplifting resolution, BPM ${bpm}, MINOR to MAJOR`;

if (/excit|awe|power|triumph/.test(ar))

return `${base}, energetic and confident, BPM ${bpm}, MAJOR`;

if (/trust|ease|clarity|reassur/.test(ar))

return `${base}, warm and reassuring, BPM ${Math.max(bpm - 5, 85)}`;

return `${base}, BPM ${bpm}, MAJOR`;

}

// ── generation (Lyria → MusicGen, detached) ──────────────────────────────────

// Returns a bgmMeta the caller folds into audio_meta:

// { path, mode, volume, provider, pid, log, target_duration_s, seed_duration_s,

// loop_count, pending:true } on success, or { disabled:true, reason }.

export function generateBgmDetached({

prompt,

durationS,

hyperframesDir,

lyriaRecipe,

seedSeconds = 28,

hasVoice,

}) {

const rel = "assets/bgm/track.wav";

const abs = join(hyperframesDir, rel);

mkdirSync(join(hyperframesDir, "assets", "bgm"), { recursive: true });

const log = join(hyperframesDir, "assets", "bgm", `bgm-${Date.now()}.log`);

const targetS = Math.max(1, durationS);

const baseMeta = { path: rel, mode: null, volume: bgmDefaultVolume(hasVoice), pending: true };

const lyriaConfigured = !!lyriaKey() && !!lyriaRecipe && existsSync(lyriaRecipe);

// Make a backend runnable: prefer Lyria when configured (install google-genai

// on demand), else ensure local MusicGen deps. Installs are synchronous here —

// generation itself is detached, so the engine still returns promptly.

if (lyriaConfigured && !pyOk(LYRIA_PY_PROBE)) pipInstall(LYRIA_PY_DEPS);

const useLyria = lyriaConfigured && pyOk(LYRIA_PY_PROBE);

if (!useLyria && !pyOk(BGM_PY_PROBE)) pipInstall(BGM_PY_DEPS);

const fd = openSync(log, "w");

if (useLyria) {

const { cmd, args } = pythonInvocation([

lyriaRecipe,

"--output",

abs,

"--duration",

String(targetS),

"--prompt",

prompt,

]);

const proc = spawn(cmd, args, { detached: true, stdio: ["ignore", fd, fd] });

proc.unref();

closeSync(fd);

return {

...baseMeta,

mode: "detached-single",

provider: "lyria",

pid: proc.pid,

log,

target_duration_s: r3(targetS),

};

}

if (pyOk(BGM_PY_PROBE)) {

const seedS = Math.min(Math.max(seedSeconds, 10), 30);

const loops = targetS > seedS ? Math.ceil(targetS / seedS) : 1;

const script = musicgenScript({ prompt, abs, targetS, seedS });

const { cmd, args } = pythonInvocation(["-c", script]);

const proc = spawn(cmd, args, { detached: true, stdio: ["ignore", fd, fd] });

proc.unref();

closeSync(fd);

return {

...baseMeta,

mode: targetS > seedS ? "detached-seed-loop" : "detached-seed-trim",

provider: "musicgen",

pid: proc.pid,

log,

target_duration_s: r3(targetS),

seed_duration_s: seedS,

loop_count: loops,

};

}

closeSync(fd);

return {

disabled: true,

reason: lyriaConfigured

? `Lyria configured but google-genai uninstallable, and local MusicGen unavailable (pip install ${BGM_PY_DEPS.join(" ")})`

: `no Lyria key/recipe and local MusicGen deps unavailable (pip install ${BGM_PY_DEPS.join(" ")})`,

};

}

// Inline MusicGen: generate ONE seed clip (≤30s to stay under the decoder's

// positional limit), then trim it down or crossfade-loop it up to the target.

function musicgenScript({ prompt, abs, targetS, seedS }) {

return `

import math, os, sys, traceback

from pathlib import Path

import numpy as np

import soundfile as sf

from transformers import MusicgenForConditionalGeneration, AutoProcessor

prompt = ${JSON.stringify(prompt)}

out_path = ${JSON.stringify(abs)}

target_s = float(${targetS.toFixed(3)})

seed_s = float(${seedS.toFixed(3)})

token_rate = 50

crossfade_s = 0.3

def apply_fade(arr, sr, fade_in_s=0.08, fade_out_s=0.5):

n_in = min(int(round(fade_in_s * sr)), arr.shape[0] // 2)

n_out = min(int(round(fade_out_s * sr)), arr.shape[0] // 2)

if n_in > 1: arr[:n_in] *= np.linspace(0.0, 1.0, n_in, dtype="float32")

if n_out > 1: arr[-n_out:] *= np.linspace(1.0, 0.0, n_out, dtype="float32")

return arr

def loop_crossfade(seed, target_len, xf):

if seed.shape[0] >= target_len: return seed[:target_len]

xf = min(xf, seed.shape[0] // 2)

if xf < 1:

reps = int(math.ceil(target_len / seed.shape[0]))

return np.tile(seed, reps)[:target_len]

t = np.linspace(0.0, 1.0, xf, dtype="float32")

fade_out = np.cos(t * (math.pi / 2)); fade_in = np.sin(t * (math.pi / 2))

out = seed.copy()

while out.shape[0] < target_len:

tail = out[-xf:] * fade_out; head = seed[:xf] * fade_in

out = np.concatenate([out[:-xf], tail + head, seed[xf:]])

return out[:target_len]

try:

Path(os.path.dirname(out_path)).mkdir(parents=True, exist_ok=True)

processor = AutoProcessor.from_pretrained("facebook/musicgen-small")

model = MusicgenForConditionalGeneration.from_pretrained("facebook/musicgen-small")

model.eval()

sr = int(model.config.audio_encoder.sampling_rate)

gen_s = min(seed_s, target_s)

tokens = max(1, int(math.ceil(gen_s * token_rate)))

print(f"[musicgen] seed dur={gen_s:.2f}s tokens={tokens}", flush=True)

inputs = processor(text=[prompt], padding=True, return_tensors="pt")

audio = model.generate(**inputs, max_new_tokens=tokens)

seed = audio[0, 0].detach().cpu().numpy().astype("float32")

peak = float(np.max(np.abs(seed)))

if peak > 1e-6: seed = seed * (0.89 / peak)

want = max(1, int(round(target_s * sr)))

if seed.shape[0] >= want:

final = seed[:want].copy()

else:

final = loop_crossfade(seed, want, int(round(crossfade_s * sr)))

if final.shape[0] < want: final = np.pad(final, (0, want - final.shape[0]))

else: final = final[:want]

final = apply_fade(final, sr)

peak = float(np.max(np.abs(final)))

if peak > 1.0: final = final / peak

sf.write(out_path, final, sr)

print(f"[musicgen] wrote {out_path} samples={final.shape[0]} sr={sr}", flush=True)

except Exception:

traceback.print_exc(); sys.exit(1)

`;

}