Complete VIDEO-001 through VIDEO-004 software video studies

tools/video002_radio_budget.py

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+"""Расчётная длительность пакета VIDEO-002; PHY и радиоприёмник не меняются."""
+
+from __future__ import annotations
+
+from dataclasses import asdict, dataclass
+import math
+
+from protocol.video_stream_transport import HEADER_SIZE
+
+
+PROTOCOL_OVERHEAD_BYTES = 12  # Заголовок protocol.packet и CRC-32.
+PREAMBLE_SYMBOLS = 1280
+PHY_HEADER_SYMBOLS = 144
+TRANSIENT_SYMBOLS = 42  # Два защитных интервала и хвост RRC.
+FEC_TAIL_BITS = 6
+RRC_ROLLOFF = 0.35
+CURRENT_MAX_PACKET_BYTES = 1024
+
+
+@dataclass(frozen=True)
+class RadioEstimate:
+    modulation: str
+    symbols_per_second: int
+    phy_payload_bytes: int
+    gap_ms: float
+    video_bytes_per_packet: int
+    packet_bytes_before_fec: int
+    coded_body_bits: int
+    airtime_ms: float
+    useful_video_bps: float
+    overhead_fraction: float
+    raw_bps: int
+    occupied_bandwidth_hz: float
+    symbol_duration_us: float
+    within_current_packet_limit: bool
+    implemented_in_current_phy: bool
+
+    def as_dict(self) -> dict:
+        return asdict(self)
+
+
+def estimate(modulation: str, symbols_per_second: int,
+             phy_payload_bytes: int, gap_ms: float) -> RadioEstimate:
+    """QPSK: преамбула/PHY-заголовок BPSK, тело FEC по два бита на символ."""
+    if modulation not in ("BPSK", "QPSK") or symbols_per_second <= 0:
+        raise ValueError("Неизвестная модуляция или символьная скорость")
+    if phy_payload_bytes <= HEADER_SIZE or gap_ms < 0:
+        raise ValueError("Недопустимые нагрузка или пауза")
+    packet_bytes = phy_payload_bytes + PROTOCOL_OVERHEAD_BYTES
+    coded_bits = 2 * (packet_bytes * 8 + FEC_TAIL_BITS)
+    bits_per_symbol = 1 if modulation == "BPSK" else 2
+    body_symbols = math.ceil(coded_bits / bits_per_symbol)
+    symbols = PREAMBLE_SYMBOLS + PHY_HEADER_SYMBOLS + body_symbols + TRANSIENT_SYMBOLS
+    airtime_ms = 1000 * symbols / symbols_per_second
+    video_bytes = phy_payload_bytes - HEADER_SIZE
+    useful_bps = video_bytes * 8000 / (airtime_ms + gap_ms)
+    # Вся ёмкость интервала, кроме байтов изображения, относится к накладным расходам.
+    overhead = 1 - useful_bps / (symbols_per_second * bits_per_symbol)
+    return RadioEstimate(
+        modulation, symbols_per_second, phy_payload_bytes, gap_ms,
+        video_bytes, packet_bytes, coded_bits, airtime_ms, useful_bps,
+        overhead, symbols_per_second * bits_per_symbol,
+        symbols_per_second * (1 + RRC_ROLLOFF),
+        1_000_000 / symbols_per_second,
+        packet_bytes <= CURRENT_MAX_PACKET_BYTES,
+        modulation == "BPSK" and symbols_per_second == 500_000
+        and phy_payload_bytes == 256 and gap_ms == 5,
+    )
+
+
+def matrix() -> list[RadioEstimate]:
+    return [estimate(modulation, speed, payload, gap)
+            for modulation, speed in (("BPSK", 500_000),
+                                      ("QPSK", 250_000),
+                                      ("QPSK", 500_000))
+            for payload in (256, 512, 1024)
+            for gap in (5, 2, 1, 0)]
+
+
+def margin_fits(rate_bps: float, peak_bps: float, margin: float) -> bool:
+    """Запас 20%: предельная скорость >= пик * 1.2."""
+    if not 0 <= margin <= 1:
+        raise ValueError("Запас вне диапазона 0–1")
+    return rate_bps >= peak_bps * (1 + margin)