CROWD-SYNC AUDIO - portable (no install, no Node, any 64-bit Windows PC)
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1. Keep the "public" folder next to CrowdSyncAudio.exe.
2. Double-click CrowdSyncAudio.exe. Allow the Windows firewall prompt (Private).
   It opens the BROADCAST page in your browser.
3. Broadcast page:
   - Pick your stereo input, Start broadcasting, allow the mic.
     (Use Edge or Chrome for the broadcast page.)
     No audio interface, or the sound plays inside the PC itself?
     See AUDIO-SETUP.md (virtual cable, step by step).
   - Type your WiFi name + password -> two QR codes appear. Put them on a
     screen/poster:  QR 1 = join WiFi,  QR 2 = open the player.
4. Guests scan QR 1 (connect), then QR 2 (opens player in their browser),
   wired headphones, tap Play.

Audio is Opus (~128 kbps/phone). Every device plays each frame at the same
moment on a shared clock, at a fixed 35 ms behind the source - that lead is
held rather than grown, so nobody slowly falls behind. Per-device output
delay (Bluetooth!) is dialled out once with the +/- nudge; it is remembered.

Crackling, dropouts, or devices out of step?  -> DIAGNOSE.md
Sound comes from the PC itself, not an interface?  -> AUDIO-SETUP.md
