Cattura: rimuovi videorate e limita la coda all'ultimo frame

La pipeline GStreamer non forza più la frequenza con videorate e usa un
appsink con max-buffers=1, drop e enable-last-sample=false: si elabora solo
il frame più recente invece di duplicare frame o accumulare ritardo.

Il demone rinnova inoltre l'ultimo frame inviato ogni 10 s quando la sorgente
a frequenza variabile non produce nuovi campioni (schermata statica),
evitando il timeout del firmware Adalight, e usa time.monotonic per il
pacing di invio al posto di time.time.

backend/ambicapture.py

@@ -79,10 +79,9 @@ class Capture:
         self.gw = leds * sub
         self.gh = rows
         desc = (f"pipewiresrc path={node} do-timestamp=true ! "
-                f"videoconvert ! videoscale ! videorate ! "
+                f"videoconvert ! videoscale ! "
-                f"video/x-raw,format=RGB,width={self.gw},height={self.gh},"
+                f"video/x-raw,format=RGB,width={self.gw},height={self.gh} ! "
-                f"framerate={int(fps)}/1 ! "
+                f"appsink name=sink emit-signals=false max-buffers=1 drop=true sync=false enable-last-sample=false")
-                f"appsink name=sink emit-signals=false max-buffers=2 drop=true sync=false")
         self.pipe = Gst.parse_launch(desc)
         self.sink = self.pipe.get_by_name("sink")
 

backend/ambilightd.py

@@ -208,6 +208,7 @@ def capture_loop(state, strip):
     last_write = 0.0
     t_log = time.time()
     n_none = 0
+    last_frame = None
     while True:
         cfg = state.snapshot()
         if not cfg["running"]:
@@ -215,6 +216,7 @@ def capture_loop(state, strip):
                 cap.stop()
                 cap = None
             prev = None
+            last_frame = None
             time.sleep(0.15)
             continue
 
@@ -239,10 +241,15 @@ def capture_loop(state, strip):
 
         frame = cap.frame(200)
         if frame is None:
+            # Una sorgente a frequenza variabile può fermarsi su una schermata
+            # statica; rinnova il frame per il timeout del firmware Adalight.
+            if last_frame is not None and time.monotonic() - last_write >= 10:
+                if strip.write(last_frame):
+                    last_write = time.monotonic()
             n_none += 1
             time.sleep(0.005)
             if time.time() - t_log >= 10:
-                log(f"diagnostica: 10 s senza frame (timeout={n_none}), "
+                log(f"diagnostica: attese cattura negli ultimi 10 s (timeout={n_none}), "
                     f"fps={state.fps} sent={sent}")
                 t_log, n_none = time.time(), 0
             continue
@@ -270,12 +277,13 @@ def capture_loop(state, strip):
         frame_bits = (6 + 3 * cfg["leds"]) * 10
         min_interval = max(1.0 / max(1, cfg["target_fps"]),
                            1.7 * frame_bits / max(9600, cfg["baud"]))
-        wait = min_interval - (time.time() - last_write)
+        wait = min_interval - (time.monotonic() - last_write)
         if wait > 0:
             time.sleep(wait)
-        ok = strip.write(adalight_frame(px))
+        last_frame = adalight_frame(px)
+        ok = strip.write(last_frame)
         if ok:
-            last_write = time.time()
+            last_write = time.monotonic()
             sent += 1
             now = time.time()
             if now - t_win >= 1.0: