From 140b4f3d6741778e8f9b774d0933af23c0915ebf Mon Sep 17 00:00:00 2001
From: Anthony Wharton <a.wharton.2015@bristol.ac.uk>
Date: Sun, 12 May 2019 18:40:28 +0100
Subject: [PATCH] Add VideoCapture class

---
 src/recorders/video_capture.py | 116 +++++++++++++++++++++++++++++++++
 1 file changed, 116 insertions(+)
 create mode 100644 src/recorders/video_capture.py

diff --git a/src/recorders/video_capture.py b/src/recorders/video_capture.py
new file mode 100644
index 0000000..d488ebe
--- /dev/null
+++ b/src/recorders/video_capture.py
@@ -0,0 +1,116 @@
+# Top level class for a video capture providing simplified API's for common
+# functions
+
+# Import required modules
+import configparser
+import cv2
+import os
+import sys
+
+"""
+Class to provide boilerplate code to build a video recorder with the
+correct settings from the config file.
+
+The internal recorder can be accessed with 'video_capture.internal'
+"""
+class VideoCapture:
+
+	"""
+	Creates a new VideoCapture instance depending on the settings in the
+	provided config file.
+
+	Config can either be a string to the path, or a pre-setup configparser.
+	"""
+	def __init__(self, config):
+		if isinstance(config, str):
+			self.config = configparser.ConfigParser()
+			self.config.read(config)
+		else:
+			self.config = config
+
+		# Check device path
+		if not os.path.exists(config.get("video", "device_path")):
+			print("Camera path is not configured correctly, " +
+				  "please edit the 'device_path' config value.")
+			sys.exit(1)
+
+		# Create reader
+		self.internal = None # The internal video recorder
+		self.fw	   = None # The frame width
+		self.fh	   = None # The frame height
+		self._create_reader()
+
+		# Request a frame to wake the camera up
+		self.internal.grab()
+
+	"""
+	Frees resources when destroyed
+	"""
+	def __del__(self):
+		if self is not None:
+			self.internal.release()
+
+	"""
+	Reads a frame, returns the frame and an attempted grayscale conversion of
+	the frame in a tuple:
+
+	(frame, grayscale_frame)
+
+	If the grayscale conversion fails, both items in the tuple are identical.
+	"""
+	def read_frame(self):
+		# Grab a single frame of video
+		# Don't remove ret, it doesn't work without it
+		ret, frame = self.internal.read()
+		if not ret:
+			print("Failed to read camera specified in your 'device_path', " +
+			      "aborting")
+			sys.exit(1)
+
+		try:
+			# Convert from color to grayscale
+			# First processing of frame, so frame errors show up here
+			gsframe = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
+		except RuntimeError:
+			gsframe = frame
+		except cv2.error:
+			print("\nAn error occurred in OpenCV\n")
+			raise
+		return frame, gsframe
+
+	"""
+	Sets up the video reader instance
+	"""
+	def _create_reader(self):
+		if self.config.get("video", "recording_plugin") == "ffmpeg":
+			# Set the capture source for ffmpeg
+			from recorders.ffmpeg_reader import ffmpeg_reader
+			self.internal = ffmpeg_reader(
+				self.config.get("video", "device_path"),
+				self.config.get("video", "device_format")
+			)
+		elif self.config.get("video", "recording_plugin") == "pyv4l2":
+			# Set the capture source for pyv4l2
+			from recorders.pyv4l2_reader import pyv4l2_reader
+			self.internal = pyv4l2_reader(
+				self.config.get("video", "device_path"),
+				self.config.get("video", "device_format")
+			)
+		else:
+			# Start video capture on the IR camera through OpenCV
+			self.internal = cv2.VideoCapture(
+				self.config.get("video", "device_path")
+			)
+
+		# Force MJPEG decoding if true
+		if self.config.getboolean("video", "force_mjpeg", fallback=False):
+			# Set a magic number, will enable MJPEG but is badly documentated
+			self.internal.set(cv2.CAP_PROP_FOURCC, 1196444237)
+
+		# Set the frame width and height if requested
+		self.fw = self.config.getint("video", "frame_width", fallback=-1)
+		self.fh = self.config.getint("video", "frame_height", fallback=-1)
+		if self.fw != -1:
+			self.internal.set(cv2.CAP_PROP_FRAME_WIDTH, self.fw)
+		if self.fh != -1:
+			self.internal.set(cv2.CAP_PROP_FRAME_HEIGHT, self.fh)