VIDEO-005: add full offline QPSK IQ video receiver

protocol/video004_erasure.py

@@ -10,7 +10,7 @@ from __future__ import annotations
 from dataclasses import dataclass, field
 from collections import deque
 import struct
-from typing import Sequence
+from typing import Sequence, cast
 
 from protocol.packet_erasure_fec import (
     InsufficientSymbolsError, _linear_combine, encode_parity_symbols,
@@ -212,7 +212,7 @@ class VideoErasureCollector:
         block.wires[symbol.index] = wire
         output = []
         if not symbol.is_parity and symbol.index not in block.delivered:
-            item = direct_item
+            item = cast(Delivery, direct_item)
             block.delivered.add(symbol.index)
             if now_ms - item.capture_ms < self.max_age_ms:
                 output.append(item)