Watch for broken frames using JPEG end bytes, and log error (68380385) · Commits · OpenFlexure / openflexure-microscope-server

openflexure_microscope/camera/base.py

+17 −0

Original line number	Diff line number	Diff line
		@@ -8,6 +8,7 @@ from typing import BinaryIO, List, NamedTuple, Optional, Tuple, Type, Union

		from labthings import ClientEvent, StrictLock

		JPEG_END_BYTES: bytes = b"\xff\xd9"

		# Class to store a frames metadata
		class TrackerFrame(NamedTuple):
		@@ -42,6 +43,8 @@ class FrameStream(io.BytesIO):
		# We use a ClientEvent so that each thread can call getvalue() independantly
		self.new_frame: ClientEvent = ClientEvent()

		self._bad_frame: bool = False

		def __enter__(self):
		self.start_tracking()
		return super().__enter__()
		@@ -79,6 +82,20 @@ class FrameStream(io.BytesIO):
		3. Store the new frame image
		4. Set the new_frame event
		"""
		# If we get a bad frame, and the last frame was good
		if s[-2:] != JPEG_END_BYTES and not self._bad_frame:
		# TODO: Handle this more cleverly. Automatically lower bitrate to compensate?
		# Log error
		logging.error(
		"Incomplete frame data recieved. Camera bandwidth may have been exceeded. Consider lowing resolution, framerate, or target bitrate."
		)
		# Record that last frame was bad
		self._bad_frame = True
		# If the last frame was bad, but this frame was good
		elif self._bad_frame and s[-2:] == JPEG_END_BYTES:
		# Clear the bad frame record
		self._bad_frame = False
		# If we're tracking frame size
		if self.tracking:
		frame = TrackerFrame(size=len(s), time=time.time())
		self.frames.append(frame)