person_detection/base_camera.py

import paho.mqtt.client as mqtt
import time
import os
import sys
import threading
import logging as log
from multiprocessing import Process, Queue, Value, Array, Lock

import roc


class BaseCamera(object):
    process = {} # background process that reads frames from camera
    frame = {} # frame queue
    activity_counter = Value('i', 0)
    cameras = Array('i', [0, 0, 0, 0])
    lock = Lock()

    def __init__(self, device, key, mbrlow, mbrhigh, devicegroup):
        self.mqttBroker = "localhost"
        self.device = device
        self.key = key
        self.mbrlow = mbrlow
        self.mbrhigh = mbrhigh
        self.devicegroup = devicegroup

        """Start the background camera process if it isn't running yet."""
        if BaseCamera.cameras[int(self.device)] == 0:
            BaseCamera.cameras[int(self.device)] = 1
            self.last_detected = None
            self.timer = None
            self.detected = False
            BaseCamera.frame[self.device] = Queue(100)
            # start background frame process
            BaseCamera.process[self.device] = Process(target=self._process, args=(self.device))
            BaseCamera.process[self.device].start()
            # wait until frames are available
            _ = self.get_frame()

    def get_frame(self):
        """Return the current camera frame."""

        # blocks
        return BaseCamera.frame[self.device].get(block=True)

    def frames(self):
        """"Generator that returns frames from the camera."""
        raise NotImplementedError('Must be implemented by subclasses.')

    def _process(self, device):
        """Camera background process."""
        frames_iterator = self.frames()
        for frame in frames_iterator:
            BaseCamera.frame[device].put(frame, block=True)

        BaseCamera.process[device] = None

    def person_detected(self, num):
        self.last_detected = time.time()
        if not self.detected:
            BaseCamera.lock.acquire()
            BaseCamera.activity_counter.value += 1
            BaseCamera.lock.release()
            self.set_resolution_high()
            roc.set_mbr(self.key, self.devicegroup, self.mbrhigh)
            self.detected = True
            self.start_timer()

    def no_person_detected(self):
        self.detected = False
        self.timer = None
        BaseCamera.lock.acquire()
        BaseCamera.activity_counter.value -=1
        if BaseCamera.activity_counter.value <= 0:
            BaseCamera.activity_counter.value = 0
            self.set_resolution_low()
            roc.set_mbr(self.key, self.devicegroup, self.mbrlow)
        BaseCamera.lock.release()


    def start_timer(self):
        # log.info("Start timer for device {}".format(device))
        self.timer = threading.Timer(10.0, self.timer_expiry)
        self.timer.start()


    def set_resolution_high(self):
        for device in range(0, 4):
            self.set_resolution(str(device), "high")


    def set_resolution_low(self):
        for device in range(0, 4):
            self.set_resolution(str(device), "low")


    def set_resolution(self, device, level):
        log.info("Setting camera {} resolution to {}".format(device, level))
        client = mqtt.Client()
        client.connect(self.mqttBroker)
        client.publish("camera/" + str(5000 + int(device)), level)


    def timer_expiry(self):
        now = time.time()
        diff = now - self.last_detected
        log.info("timer_expiry() - now:{}, last_detected:{}".format(now, self.last_detected))
        if diff > 5.0:
            self.no_person_detected()
        else:
            # Restart timer since person detected not too long back
            self.start_timer()