fix: reduce viz decay to 3 frames, add max-age safety cap, add FPS stats

- DECAY_FRAMES default 8→3 (100ms visual trail)
- MAX_NOTE_AGE safety cap: force-expire notes after 15 frames
- Track note age separately from decay to prevent stale notes
- Add FPS and active_notes to viz stats for diagnostics
- Fix router reconnect: unregister old fd, not new one

scripts/led-matrix-viz.py

@@ -7,7 +7,8 @@ import socket, msgpack, time, os, select, collections
 
 VIZ_PORT = int(os.environ.get("VIZ_PORT", "8082"))
 ROUTER_SOCK = os.environ.get("ROUTER_SOCK", "/var/run/arduino-router.sock")
-DECAY_FRAMES = int(os.environ.get("DECAY_FRAMES", "8"))
+DECAY_FRAMES = int(os.environ.get("DECAY_FRAMES", "3"))
+MAX_NOTE_AGE = int(os.environ.get("MAX_NOTE_AGE", "15"))
 
 COLS = 13
 ROWS = 8
@@ -23,8 +24,6 @@ POLLOUT = select.POLLOUT
 SOCK_BUFFER = 4096
 ROUTER_RECONNECT_DELAY = 0.1
 
-_frame_hooks = []  # for metrics
-
 
 def pack_frame(pixels):
     bits = 0
@@ -87,7 +86,6 @@ def main():
     next_frame_time = time.monotonic()
 
     pending_frames = FrameQueue(maxsize=5)
-    router_registered = False
     router_fd = router.fileno()
     _poll.register(router, POLLIN | POLLOUT)
 
@@ -95,6 +93,8 @@ def main():
     frames_dropped = 0
     router_errors = 0
     stats_last_write = time.monotonic()
+    fps_sample_start = time.monotonic()
+    fps_sample_frames = 0
 
     while True:
         now = time.monotonic()
@@ -127,7 +127,7 @@ def main():
                         vel = int(parts[3]) if len(parts) >= 4 else 0
                         msg_type = status & 0xF0
                         if msg_type == 0x90 and vel > 0:
-                            active_notes[note] = DECAY_FRAMES
+                            active_notes[note] = {"decay": DECAY_FRAMES, "age": 0}
                         elif msg_type == 0x80 or (msg_type == 0x90 and vel == 0):
                             active_notes.pop(note, None)
 
@@ -153,26 +153,32 @@ def main():
                         router_errors += 1
                         pending_frames.push(frame)
                         time.sleep(ROUTER_RECONNECT_DELAY)
+                        old_fd = router_fd
                         try:
                             router.close()
                         except OSError:
                             pass
                         router = connect_router()
                         router_fd = router.fileno()
-                        _poll.unregister(router)
+                        try:
+                            _poll.unregister(old_fd)
+                        except (KeyError, OSError):
+                            pass
                         _poll.register(router, POLLIN | POLLOUT)
 
         # Render frame when due
         if now >= next_frame_time:
             next_frame_time = now + frame_interval
+            fps_sample_frames += 1
 
             pixels = [[0] * COLS for _ in range(ROWS)]
             expired = []
-            for note, decay in list(active_notes.items()):
-                if decay <= 0:
+            for note, state in list(active_notes.items()):
+                state["age"] += 1
+                state["decay"] -= 1
+                if state["decay"] <= 0 or state["age"] > MAX_NOTE_AGE:
                     expired.append(note)
                     continue
-                active_notes[note] = decay - 1
                 note_min, note_max = 36, 96
                 row = 7 - int((note - note_min) / (note_max - note_min) * 7)
                 row = max(0, min(7, row))
@@ -195,14 +201,14 @@ def main():
 
             # Write stats periodically (every 2s)
             if now - stats_last_write >= 2.0:
-                _write_stats(frames_sent, frames_dropped, pending_frames)
+                fps = fps_sample_frames / (now - fps_sample_start) if (now - fps_sample_start) > 0 else 0
+                _write_stats(frames_sent, frames_dropped, pending_frames, fps, len(active_notes))
                 stats_last_write = now
+                fps_sample_start = now
+                fps_sample_frames = 0
 
 
-_stats_last_write = 0.0
-
-
-def _write_stats(sent, dropped, pending):
+def _write_stats(sent, dropped, pending, fps, active_count):
     import json
     try:
         with open(STATS_FILE, "w") as f:
@@ -211,6 +217,8 @@ def _write_stats(sent, dropped, pending):
                 "frames_dropped": dropped,
                 "pending_queue": len(pending),
                 "queue_full": pending.full(),
+                "fps": round(fps, 1),
+                "active_notes": active_count,
                 "ts": time.time()
             }, f)
     except OSError: