wuzhuorong
40fd3089a7
- 实现RTSP流接入服务(rtsp_service)，支持单路流连接/解码/帧采集 - 实现多路流调度管理器(stream_manager)，统一管理多路RTSP流启停与状态监控
255 lines
7.5 KiB
Python
255 lines
7.5 KiB
Python
"""帧缓冲区 (MVP-2 / D15)
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基于 Ring Buffer 的帧缓冲，配合丢帧策略，避免多路 RTSP 流场景下
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内存无限增长。
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核心设计:
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1. 固定容量的环形缓冲区，写满后自动覆盖最旧帧
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2. 支持按策略丢帧: 最新帧优先 (实时性) / 均匀采样 (覆盖率)
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3. 线程安全: 使用 asyncio.Lock 保护并发读写
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4. 帧元数据: 每帧附带 stream_id / timestamp / frame_index
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"""
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from __future__ import annotations
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import asyncio
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import logging
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import time
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from collections import deque
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from dataclasses import dataclass, field
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from enum import Enum
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from typing import Any, Dict, List, Optional, Tuple
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import numpy as np
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logger = logging.getLogger(__name__)
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class DropPolicy(str, Enum):
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"""丢帧策略。"""
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LATEST = "latest" # 保留最新帧，覆盖最旧帧 (默认，适合实时检测)
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SAMPLE = "sample" # 均匀采样保留，丢弃中间帧 (适合回溯分析)
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@dataclass
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class FrameMeta:
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"""帧元数据。"""
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stream_id: str
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frame_index: int
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timestamp: float
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width: int = 0
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height: int = 0
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@dataclass
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class FrameItem:
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"""缓冲区中的帧条目。"""
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frame: np.ndarray
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meta: FrameMeta
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class FrameBuffer:
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"""环形帧缓冲区。
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Args:
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capacity: 缓冲区最大帧数
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drop_policy: 丢帧策略
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max_memory_mb: 内存上限 (MB)，超过时强制丢帧；0 表示不限制
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"""
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def __init__(
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self,
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capacity: int = 300,
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drop_policy: DropPolicy = DropPolicy.LATEST,
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max_memory_mb: float = 0,
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) -> None:
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self.capacity = max(1, capacity)
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self.drop_policy = drop_policy
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self.max_memory_mb = max(0.0, max_memory_mb)
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self._buffer: deque[FrameItem] = deque(maxlen=self.capacity)
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self._lock = asyncio.Lock()
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self._total_written: int = 0
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self._total_dropped: int = 0
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# ------------------------------------------------------------------
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# 写入
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# ------------------------------------------------------------------
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async def write(
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self,
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frame: np.ndarray,
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stream_id: str,
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frame_index: int,
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timestamp: Optional[float] = None,
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) -> None:
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"""写入一帧到缓冲区。
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当缓冲区已满时，根据 ``drop_policy`` 决定丢弃策略。
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"""
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meta = FrameMeta(
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stream_id=stream_id,
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frame_index=frame_index,
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timestamp=timestamp or time.time(),
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width=frame.shape[1] if frame.ndim >= 2 else 0,
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height=frame.shape[0] if frame.ndim >= 2 else 0,
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)
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item = FrameItem(frame=frame, meta=meta)
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async with self._lock:
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self._total_written += 1
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if len(self._buffer) >= self.capacity:
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self._apply_drop_policy(item)
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else:
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self._buffer.append(item)
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# 内存上限检查
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if self.max_memory_mb > 0:
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self._enforce_memory_limit()
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# ------------------------------------------------------------------
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# 读取
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# ------------------------------------------------------------------
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async def read_latest(self) -> Optional[FrameItem]:
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"""读取最新一帧 (不消费)。"""
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async with self._lock:
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if not self._buffer:
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return None
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return self._buffer[-1]
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async def read_oldest(self) -> Optional[FrameItem]:
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"""读取最旧一帧 (不消费)。"""
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async with self._lock:
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if not self._buffer:
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return None
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return self._buffer[0]
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async def read_all(self) -> List[FrameItem]:
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"""读取缓冲区所有帧 (快照，不消费)。"""
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async with self._lock:
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return list(self._buffer)
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async def read_range(
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self,
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start_index: int = 0,
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count: Optional[int] = None,
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) -> List[FrameItem]:
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"""读取指定范围的帧 (快照)。
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Args:
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start_index: 从缓冲区开头的偏移量
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count: 读取帧数，None 表示到末尾
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"""
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async with self._lock:
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items = list(self._buffer)
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if start_index >= len(items):
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return []
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end = len(items) if count is None else start_index + count
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return items[start_index:end]
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async def pop_latest(self) -> Optional[FrameItem]:
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"""弹出最新一帧 (消费)。"""
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async with self._lock:
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if not self._buffer:
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return None
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return self._buffer.pop()
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async def pop_oldest(self) -> Optional[FrameItem]:
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"""弹出最旧一帧 (消费)。"""
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async with self._lock:
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if not self._buffer:
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return None
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return self._buffer.popleft()
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# ------------------------------------------------------------------
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# 状态
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# ------------------------------------------------------------------
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async def clear(self) -> None:
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"""清空缓冲区。"""
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async with self._lock:
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self._buffer.clear()
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@property
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def size(self) -> int:
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"""当前缓冲区帧数。"""
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return len(self._buffer)
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@property
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def stats(self) -> Dict[str, Any]:
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"""缓冲区统计信息。"""
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return {
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"size": len(self._buffer),
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"capacity": self.capacity,
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"total_written": self._total_written,
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"total_dropped": self._total_dropped,
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"drop_policy": self.drop_policy.value,
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"usage_percent": round(len(self._buffer) / self.capacity * 100, 1),
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}
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def estimate_memory_mb(self) -> float:
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"""估算当前缓冲区占用内存 (MB)。"""
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if not self._buffer:
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return 0.0
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# 取第一帧估算单帧大小
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sample = self._buffer[0].frame
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frame_bytes = sample.nbytes if isinstance(sample, np.ndarray) else 0
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return len(self._buffer) * frame_bytes / (1024 * 1024)
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# ------------------------------------------------------------------
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# 内部
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# ------------------------------------------------------------------
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def _apply_drop_policy(self, new_item: FrameItem) -> None:
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"""缓冲区满时应用丢帧策略。"""
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if self.drop_policy == DropPolicy.LATEST:
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# 覆盖最旧帧 (deque maxlen 自动处理)
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self._total_dropped += 1
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self._buffer.append(new_item)
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elif self.drop_policy == DropPolicy.SAMPLE:
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# 均匀采样: 丢弃偶数位置的帧，腾出空间
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sampled = deque(maxlen=self.capacity)
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step = 2
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for i, item in enumerate(self._buffer):
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if i % step != 0:
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self._total_dropped += 1
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else:
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sampled.append(item)
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sampled.append(new_item)
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self._buffer = sampled
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def _enforce_memory_limit(self) -> None:
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"""强制执行内存上限，超出时丢弃最旧帧。"""
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while self.max_memory_mb > 0 and self._buffer:
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current_mb = self.estimate_memory_mb()
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if current_mb <= self.max_memory_mb:
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break
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self._buffer.popleft()
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self._total_dropped += 1
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logger.debug(
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"FrameBuffer 内存超限 (%.1f > %.1f MB)，丢弃最旧帧",
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current_mb,
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self.max_memory_mb,
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)
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__all__ = ["FrameBuffer", "FrameItem", "FrameMeta", "DropPolicy"]
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