working on todo.md features

tools/mock_udpstreamer.py

@@ -240,6 +240,18 @@ def main():
         "opposite side of zero, so --quiet-at is its last zero crossing: the shape a "
         "dropout trigger is read against. -1 = never",
     )
+    ap.add_argument(
+        "--blackout-at",
+        type=float,
+        default=0.0,
+        help="seconds after start at which the stream goes silent (EMI link loss)",
+    )
+    ap.add_argument(
+        "--blackout",
+        type=float,
+        default=0.0,
+        help="seconds the stream stays silent; must exceed the client's 2 s silence timeout",
+    )
     ap.add_argument(
         "--drop-every",
         type=int,
@@ -324,6 +336,8 @@ def main():
     held = None  # (counter, datagram, release_deadline) built but withheld, for --reorder-every
     drop_left = 0
     dropped = 0
+    blackout_left = 0.0
+    blackout_done = False
     inverted = 0
     noted_drop = False
     noted_reorder = False
@@ -357,6 +371,33 @@ def main():
             continue
 
         now = time.monotonic()
+        # An EMI-style link loss: the producer keeps making samples but nothing gets
+        # through, so the client's silence timeout -- not a polite DISCONNECT -- is
+        # what ends the session, which is the case recovery has to survive.
+        if blackout_left > 0.0:
+            blackout_left -= 0.002  # the loop polls at most every 2 ms
+            if blackout_left <= 0.0:
+                print("mock udpstreamer: blackout over, resuming", flush=True)
+        elif (
+            args.blackout_at > 0.0
+            and args.blackout > 0.0
+            and not blackout_done
+            and started is not None
+            and now - started >= args.blackout_at
+        ):
+            blackout_done = True
+            blackout_left = args.blackout
+            print(
+                f"mock udpstreamer: blackout for {args.blackout} s (link loss)",
+                flush=True,
+            )
+
+        if blackout_left > 0.0:
+            # Silent: the producer falls behind the wall clock, and when the link
+            # returns it resumes from *now* -- the backlog is what the link ate.
+            next_send = now
+            time.sleep(0.002)
+            continue
         if now < next_send:
             time.sleep(min(next_send - now, 0.002))
             continue