使用 OpenCv 和 PiCamera（python）的低 FPS

Question

我正在尝试将我的 OpenCV 程序与我的 Raspberry Pi PiCamera 接口。每次我使用 OpenCV 捕获视频时，它都会大幅降低 FPS。当我使用 PiCamera 的库捕捉视频时，一切都很好。

1. 为什么会这样？
2. 有办法解决吗？

这是我的代码：

import time
import RPi.GPIO as GPIO
from PCA9685 import PCA9685
import numpy as np
import cv2

try:


    cap = cv2.VideoCapture(0)
    cap.set(cv2.CAP_PROP_FPS, 90)
    cap.set(cv2.CAP_PROP_FRAME_WIDTH, 800)
    cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 700)

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

        cv2.imshow('frame',frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

# When everything is done, release the capture


except:
    pwm.exit_PCA9685()
    print ("\nProgram end")
    exit()
cap.release()
cv2.destroyAllWindows()

这是我遇到的错误：

Answer 1

1. 首先，这些是警告而不是错误。

2. 减小视频尺寸。指定尺寸。

3. cv2.VideoCapture 存在一些问题，因为它会缓冲帧，并且帧会排队，因此如果您正在执行一些处理并且速度小于VideoCapture 的带宽，视频将会变慢。

所以，这是一个无缓冲的VideoCapture。

video_capture_Q_buf.py

import cv2, queue as Queue, threading, time


is_frame = True
# bufferless VideoCapture


class VideoCaptureQ:

    def __init__(self, name):
        self.cap = cv2.VideoCapture(name)
        self.q = Queue.Queue()
        t = threading.Thread(target=self._reader)
        t.daemon = True
        t.start()

    # read frames as soon as they are available, keeping only most recent one
    def _reader(self):
        while True:
            ret, frame = self.cap.read()
            if not ret:
                global is_frame
                is_frame = False
                break
            if not self.q.empty():
                try:
                    self.q.get_nowait()   # discard previous (unprocessed) frame
                except Queue.Empty:
                    pass
            self.q.put(frame)

    def read(self):
        return self.q.get()

使用它：

test.py

import video_capture_Q_buf as vid_cap_q # import as alias
from video_capture_Q_buf import VideoCaptureQ # class import
import time

cap = VideoCaptureQ(vid_path)

while True:

    t1 = time.time()

    if vid_cap_q.is_frame == False:
        print('no more frames left')
        break

    try:
        ori_frame = cap.read()
        # do your stuff
    except Exception as e:
        print(e)
        break
    t2 = time.time()
    print(f'FPS: {1/(t2-t1)}')