fix: 修复时间戳显示

backend/monitoring/services.py

@@ -22,6 +22,10 @@ OMNISOCKET_CONFIG_PATH = PROJECT_ROOT / "config" / "omnisocket_demo.yaml"
 VIDEO_SOURCE_MODE = os.getenv("VIDEO_SOURCE_MODE", "auto").strip().lower()
 OMNISOCKET_FRAME_FRESH_SECONDS = 2.0
 VIDEO_TIMESTAMP_SAMPLE_SIZE = 10
+VIDEO_TIMESTAMP_TRAILER_BYTES = 8
+VIDEO_TIMESTAMP_ENDIANNESS = "little"
+VIDEO_TIMESTAMP_UNIT = "ms"
+VIDEO_TIMESTAMP_MULTIPLIER_NS = 1_000_000
 VIDEO_TIMESTAMP_MAX_SKEW_NS = 7 * 24 * 60 * 60 * 1_000_000_000
 
 
@@ -211,16 +215,35 @@ class OmniSocketVideoReceiver:
             return frame[8:]
         return None
 
-    def _extract_jpeg_frame(self, frame: bytes) -> bytes | None:
+    def _split_jpeg_frame_and_trailer(self, frame: bytes) -> tuple[bytes, bytes] | None:
         jpeg_payload = self._extract_jpeg_payload(frame)
         if jpeg_payload is None:
             return None
 
+        # 当前发送端协议是 JPEG 末尾固定追加 8 字节 little-endian 毫秒时间戳。
+        if jpeg_payload.endswith(b"\xff\xd9"):
+            return jpeg_payload, b""
+
+        if (
+            len(jpeg_payload) >= VIDEO_TIMESTAMP_TRAILER_BYTES + 2
+            and jpeg_payload[-(VIDEO_TIMESTAMP_TRAILER_BYTES + 2) : -VIDEO_TIMESTAMP_TRAILER_BYTES] == b"\xff\xd9"
+        ):
+            return jpeg_payload[:-VIDEO_TIMESTAMP_TRAILER_BYTES], jpeg_payload[-VIDEO_TIMESTAMP_TRAILER_BYTES:]
+
+        # 兜底兼容旧格式，避免直接丢帧。
         eoi_index = jpeg_payload.rfind(b"\xff\xd9")
         if eoi_index < 0:
-            return jpeg_payload
+            return jpeg_payload, b""
 
-        return jpeg_payload[: eoi_index + 2]
+        trailer_start = eoi_index + 2
+        return jpeg_payload[:trailer_start], jpeg_payload[trailer_start:]
+
+    def _extract_jpeg_frame(self, frame: bytes) -> bytes | None:
+        split_payload = self._split_jpeg_frame_and_trailer(frame)
+        if split_payload is None:
+            return None
+        jpeg_frame, _ = split_payload
+        return jpeg_frame
 
     def _extract_sequence(self, frame: bytes) -> int | None:
         if len(frame) >= 8 and not frame.startswith(b"\xff\xd8"):
@@ -228,50 +251,26 @@ class OmniSocketVideoReceiver:
         return None
 
     def _extract_frame_tail(self, frame: bytes) -> bytes:
-        jpeg_payload = self._extract_jpeg_payload(frame)
-        if jpeg_payload is None:
+        split_payload = self._split_jpeg_frame_and_trailer(frame)
+        if split_payload is None:
             return b""
-
-        eoi_index = jpeg_payload.rfind(b"\xff\xd9")
-        if eoi_index < 0:
-            return b""
-
-        trailer_start = eoi_index + 2
-        if trailer_start >= len(jpeg_payload):
-            return b""
-
-        return jpeg_payload[trailer_start:]
+        _, trailer = split_payload
+        return trailer
 
     def _extract_frame_timestamp(self, frame: bytes) -> tuple[int, str, str] | None:
         trailer = self._extract_frame_tail(frame)
-        if len(trailer) < 8:
+        if len(trailer) != VIDEO_TIMESTAMP_TRAILER_BYTES:
             return None
 
-        now_ns = time.time_ns()
-        raw_timestamp = trailer[-8:]
-        best_candidate: tuple[int, str, str] | None = None
-        best_distance_ns: int | None = None
-
-        for endianness in ("big", "little"):
-            value = int.from_bytes(raw_timestamp, endianness, signed=True)
+        value = int.from_bytes(trailer, VIDEO_TIMESTAMP_ENDIANNESS, signed=False)
         if value <= 0:
-                continue
+            return None
 
-            for unit, multiplier in (
-                ("ns", 1),
-                ("us", 1_000),
-                ("ms", 1_000_000),
-                ("s", 1_000_000_000),
-            ):
-                timestamp_ns = value * multiplier
-                distance_ns = abs(now_ns - timestamp_ns)
-                if distance_ns > VIDEO_TIMESTAMP_MAX_SKEW_NS:
-                    continue
-                if best_distance_ns is None or distance_ns < best_distance_ns:
-                    best_distance_ns = distance_ns
-                    best_candidate = (timestamp_ns, unit, endianness)
+        timestamp_ns = value * VIDEO_TIMESTAMP_MULTIPLIER_NS
+        if abs(time.time_ns() - timestamp_ns) > VIDEO_TIMESTAMP_MAX_SKEW_NS:
+            return None
 
-        return best_candidate
+        return timestamp_ns, VIDEO_TIMESTAMP_UNIT, VIDEO_TIMESTAMP_ENDIANNESS
 
     def _run(self) -> None:
         # 后台持续接收循环：