Use us not ns for picamera timestamp and fix descriptor typing

src/openflexure_microscope_server/things/camera/__init__.py

@@ -16,7 +16,7 @@ from abc import ABC, abstractmethod
 from copy import deepcopy
 from datetime import datetime
 from types import TracebackType
-from typing import Any, Literal, Mapping, Optional, Self
+from typing import Any, Literal, Mapping, Optional, Self, Union, overload
 
 import numpy as np
 import piexif
@@ -223,7 +223,7 @@ class MJPEGStreamWithTimestamp(lt.outputs.MJPEGStream):
     rather than take the time it is added into the ring buffer.
     """
 
-    def add_frame(self, frame: bytes, timestamp: Optional[datetime]) -> None:
+    def add_frame(self, frame: bytes, timestamp: Optional[datetime] = None) -> None:
         """Add a JPEG to the MJPEG stream.
 
         Modify the standard function to have an option to send in the capture time.
@@ -250,12 +250,23 @@ class MJPEGStreamWithTimestamp(lt.outputs.MJPEGStream):
                 self.notify_new_frame, entry.index
             )
 
+
 class MJPEGStreamDescriptorWithTimestamp(lt.outputs.MJPEGStreamDescriptor):
     """Subclass the Labthings descriptor to return our own class."""
 
+    @overload
+    def __get__(self, obj: Literal[None], type: type | None = None) -> Self: ...
+
+    @overload
     def __get__(
-        self, obj: Optional[lt.Thing], type: type[lt.Thing] | None = None  # noqa: A002
-    ) -> MJPEGStreamWithTimestamp | Self:
+        self, obj: lt.Thing, type: type | None = None
+    ) -> MJPEGStreamWithTimestamp: ...
+
+    def __get__(
+        self,
+        obj: Optional[lt.Thing],
+        type: type[lt.Thing] | None = None,  # noqa: A002
+    ) -> Union[MJPEGStreamWithTimestamp | Self]:
         """Return our own MJPEG Stream with timestamp."""
         if obj is None:
             return self

src/openflexure_microscope_server/things/camera/picamera.py

@@ -101,10 +101,10 @@ class PicameraStreamOutput(Output):
         if timestamp is None or self.encoder.firsttimestamp is None:
             frame_timestamp = None
         else:
-            # Reconstruct full CPU time of the frame in ns
+            # Reconstruct full CPU time of the frame in us
             timestamp += self.encoder.firsttimestamp
             # Convert to datetime
-            frame_timestamp = datetime.fromtimestamp(self.cpu_dt + timestamp / 1e9)
+            frame_timestamp = datetime.fromtimestamp(self.cpu_dt + timestamp / 1e6)
         self.stream.add_frame(frame, frame_timestamp)