From 518092b1222b7d867947ffcd03146f1103f4ef80 Mon Sep 17 00:00:00 2001
From: "prompt.ac/@jeffrey" <mail@aesthetic.computer>
Date: Sun, 16 Aug 2026 13:01:47 -0400
Subject: [PATCH] =?UTF-8?q?A=20beat=20whose=20whole=20job=20is=20QA:=20ste?=
 =?UTF-8?q?reo-sync-beat=20renders=2060=20s=20of=20120=20BPM=20ping-pong?=
 =?UTF-8?q?=20=E2=80=94=201=20kHz=20left-only=20ticks=20for=20Neo,=201.8?=
 =?UTF-8?q?=20kHz=20right-only=20tocks=20for=20Blueberry,=20every=208th=20?=
 =?UTF-8?q?bar=20center-hitting=20both=20channels=20at=201.4=20kHz=20?=
 =?UTF-8?q?=E2=80=94=20so=20the=20room's=20split=20play=20can=20be=20judge?=
 =?UTF-8?q?d=20by=20ear:=20a=20limp=20in=20the=20ping-pong=20is=20machine-?=
 =?UTF-8?q?to-machine=20drift,=20a=20flam=20on=20the=20center=20bars=20is?=
 =?UTF-8?q?=20desync?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 pop/synctest/bin/render-sync-beat.mjs | 77 +++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 pop/synctest/bin/render-sync-beat.mjs

diff --git a/pop/synctest/bin/render-sync-beat.mjs b/pop/synctest/bin/render-sync-beat.mjs
new file mode 100644
index 000000000..2ca48aa88
--- /dev/null
+++ b/pop/synctest/bin/render-sync-beat.mjs
@@ -0,0 +1,77 @@
+#!/usr/bin/env node
+// stereo-sync-beat — QA track for the Juke's room-audio split play.
+//
+// 120 BPM, 60 s. Beats 1 & 3 are a LEFT-only 1 kHz tick (Neo's channel),
+// beats 2 & 4 a RIGHT-only 1.8 kHz tock (Blueberry's), so machine-to-machine
+// timing smear is instantly audible as a limp in the ping-pong. Every 8th
+// bar plays all four beats in BOTH channels at 1.4 kHz — the simultaneity
+// check: those must land as ONE hit in the room, not a flam.
+//
+//   node pop/synctest/bin/render-sync-beat.mjs
+//   → pop/synctest/out/stereo-sync-beat.{wav,mp3}
+
+import { execFileSync } from "node:child_process";
+import { mkdirSync, writeFileSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const OUT = join(dirname(fileURLToPath(import.meta.url)), "..", "out");
+mkdirSync(OUT, { recursive: true });
+
+const SR = 48000;
+const BPM = 120;
+const SECONDS = 60;
+const beat = (60 / BPM) * SR; // samples per beat
+const total = SECONDS * SR;
+const L = new Float32Array(total);
+const R = new Float32Array(total);
+
+function hit(buf, start, hz, seconds = 0.045, amp = 0.85) {
+  const n = Math.min(Math.floor(seconds * SR), total - start);
+  for (let i = 0; i < n; i++) {
+    const env = Math.exp((-5 * i) / n); // sharp pluck
+    buf[start + i] += Math.sin((2 * Math.PI * hz * i) / SR) * env * amp;
+  }
+}
+
+const beats = Math.floor(total / beat);
+for (let b = 0; b < beats; b++) {
+  const start = Math.round(b * beat);
+  const bar = Math.floor(b / 4);
+  const inBar = b % 4;
+  if ((bar + 1) % 8 === 0) {
+    hit(L, start, 1400);
+    hit(R, start, 1400); // center: must be ONE hit in the room
+  } else if (inBar === 0 || inBar === 2) {
+    hit(L, start, 1000); // Neo speaks
+  } else {
+    hit(R, start, 1800); // Blueberry answers
+  }
+}
+
+// 16-bit interleaved WAV
+const pcm = Buffer.alloc(total * 4);
+for (let i = 0; i < total; i++) {
+  pcm.writeInt16LE(Math.max(-32767, Math.min(32767, Math.round(L[i] * 32767))), i * 4);
+  pcm.writeInt16LE(Math.max(-32767, Math.min(32767, Math.round(R[i] * 32767))), i * 4 + 2);
+}
+const header = Buffer.alloc(44);
+header.write("RIFF", 0);
+header.writeUInt32LE(36 + pcm.length, 4);
+header.write("WAVEfmt ", 8);
+header.writeUInt32LE(16, 16);
+header.writeUInt16LE(1, 20);
+header.writeUInt16LE(2, 22);
+header.writeUInt32LE(SR, 24);
+header.writeUInt32LE(SR * 4, 28);
+header.writeUInt16LE(4, 32);
+header.writeUInt16LE(16, 34);
+header.write("data", 36);
+header.writeUInt32LE(pcm.length, 40);
+
+const wav = join(OUT, "stereo-sync-beat.wav");
+writeFileSync(wav, Buffer.concat([header, pcm]));
+const mp3 = join(OUT, "stereo-sync-beat.mp3");
+execFileSync("ffmpeg", ["-y", "-i", wav, "-codec:a", "libmp3lame", "-b:a", "320k", mp3],
+             { stdio: "ignore" });
+console.log(`wrote ${wav} and ${mp3}`);
-- 
2.51.2