kraken/backend/device/video.py

""" Common function for camera based method """
from fractions import Fraction
import json
import logging
import os
import time
import threading

import cv2
import numpy as np

from settings.config import settings

logger = logging.getLogger(__name__)


class VideoCaptureThread:
    def __init__(self, output_path, video_source=0, sync_device=None):
        super(VideoCaptureThread, self).__init__()
        self.video_source = video_source
        self.cap = cv2.VideoCapture(self.video_source)
        
        self.sync_device = sync_device
        
        self.output_path = output_path
        frame_size = (int(self.cap.get(cv2.CAP_PROP_FRAME_WIDTH)),
                    int(self.cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))
        self.out = cv2.VideoWriter(output_path, cv2.VideoWriter_fourcc(*'avc1'), 20.0, frame_size)

        self.videothread = threading.Thread(target=self.run)
        self.videothread.start()

    def run(self):
        logger.info("Camera starting")
        self.capture_video()
    
    def capture_video(self):
        while not self.cap.isOpened():
            pass  # Wait for the capture to be initialized
        
        # synchronize
        if self.sync_device is not None:
            self.sync_device.send_trigger(0xff)  # 255 for video ready

        while True:
            ret, frame = self.cap.read()

            # TODO: online analysis  (500ms step, asychronize)

            if not ret:
                logger.error("Error: Couldn't read frame. Exit.")
                break

            self.out.write(frame)

    def close(self):
        logger.info("Camera ended")
        self.cap.release()
        self.out.release()
        self.videothread.join()