如何使用cv2& amp;从视频并行获取帧python中的多处理 [英] how to get frames from video in parallel using cv2 & multiprocessing in python
问题描述
我一直在使用cv2&在python中进行多处理,最后我有了一个工作脚本,一旦它们已经在输入队列中,它们就会对各个帧进行填充.但是,我想首先通过使用多个内核来加快将帧放入队列的速度,因此我尝试使用相同的多处理方法将每个图像读入队列.我似乎无法使它正常工作,我不确定为什么.我以为可能是因为我正在尝试写入一个队列,所以我将它们拆分了,但是现在我想知道是否是因为我正在尝试同时读取同一视频文件.
I've been working with cv2 & multiprocessing in python, and I finally have a working script that does stuff to the individual frames once they are already in an input queue. However, I wanted to speed up getting the frames into the queue in the first place by using multiple cores, so I tried to use the same multiprocessing approach to read each image into the queue. I can't seem to get this to work though, and I'm not sure why. I thought maybe it was because I was trying to write to one queue, so I split those up, but now I'm wondering if it's because I'm trying to read from the same video file at the same time.
这是我希望用伪代码完成的事情:
Here is what I am hoping to accomplish in pseudocode:
for process in range(processCount):
start a process that does this:
for frame in range(startFrame,endFrame):
set next frame to startFrame
read frame
add frame to queue
这是我当前的代码.我已经尝试过使用泳池&单独的进程,但是现在我坚持使用单独的进程,因为我不确定问题是否出在队列管理上.如果我手动调用getFrame,我会将正确的东西放入队列,因此我认为该功能本身可以正常工作.
Here is my current code. I've tried using pool & separate processes, but for now I'm sticking to separate processes because I'm not sure if the problem is with queue management. If I call getFrame manually, I get the right stuff into the queue, so I think that function by itself works okay.
我确定我所做的事情确实很愚蠢(或者很奇怪).有人可以提出解决方案吗?最好只有一个队列...我只有两个队列来尝试解决问题.
I'm sure I'm doing something really silly (or really odd). Can someone suggest a solution? It would be great to just have one queue as well... I just had two to try to break down the problem.
谢谢.
import numpy as np
import cv2
import multiprocessing as mp
import time
def getFrame(queue, startFrame, endFrame):
for frame in range(startFrame, endFrame):
cap.set(1,frame)
frameNo = int(cap.get(0))
ret, frame = cap.read()
queue.put((frameNo,frame))
file = 'video.mov'
cap = cv2.VideoCapture(file)
fileLen = int(cap.get(7))
# get cpuCount for processCount
processCount = mp.cpu_count()/3
inQ1 = mp.JoinableQueue() # not sure if this is right queue type, but I also tried mp.Queue()
inQ2 = mp.JoinableQueue()
qList = [inQ1,inQ2]
# set up bunches
bunches = []
for startFrame in range(0,fileLen,fileLen/processCount):
endFrame = startFrame + fileLen/processCount
bunches.append((startFrame,endFrame))
getFrames = []
for i in range(processCount):
getFrames.append(mp.Process(target=getFrame, args=(qList[i], bunches[i][0],bunches[i][1],)))
for process in getFrames:
process.start()
results1 = [inQ1.get() for p in range(bunches[0][0],bunches[0][1])]
results2 = [inQ2.get() for p in range(bunches[1][0],bunches[1][1])]
inQ1.close()
inQ2.close()
cap.release()
for process in getFrames:
process.terminate()
process.join()
推荐答案
代码中确实存在一个错误:跨进程使用相同的VideoCapture
对象.显然,文件中当前正在读取的位置存在冲突.
There is indeed a mistake in the code : the use of the same VideoCapture
object across processes. Obviously there's a conflict on the position currently being read in the file.
话虽这么说,当试图为每个进程实例化一个VideoCapture时,我的解释器崩溃了(用python3.4.2
+ opencv3.0.0-beta
和python2.7.6
+ opencv2.4.8
测试).到目前为止,这是我的尝试,如果您想检查一下或继续试一下.
This being said, when trying to instantiate one VideoCapture per process, my interpreter crashes (tested with python3.4.2
+ opencv3.0.0-beta
, and python2.7.6
+ opencv2.4.8
). Here's my try so far if you want to check it / go further.
import cv2
import multiprocessing as mp
def getFrame(queue, startFrame, endFrame):
cap = cv2.VideoCapture(file) # crashes here
print("opened capture {}".format(mp.current_process()))
for frame in range(startFrame, endFrame):
# cap.set(cv2.CAP_PROP_POS_FRAMES, frame) # opencv3
cap.set(cv2.cv.CV_CAP_PROP_POS_FRAMES, frame)
# frameNo = int(cap.get(cv2.CAP_PROP_POS_FRAMES)) # opencv3
frameNo = int(cap.get(cv2.cv.CV_CAP_PROP_POS_FRAMES))
ret, f = cap.read()
if ret:
print("{} - put ({})".format(mp.current_process(), frameNo))
queue.put((frameNo, f))
cap.release()
file = "video.mov"
capture_temp = cv2.VideoCapture(file)
# fileLen = int((capture_temp).get(cv2.CAP_PROP_FRAME_COUNT)) # opencv3
fileLen = int((capture_temp).get(cv2.cv.CV_CAP_PROP_FRAME_COUNT))
capture_temp.release()
# get cpuCount for processCount
# processCount = mp.cpu_count() / 3
processCount = 2
inQ1 = mp.JoinableQueue() # not sure if this is right queue type, but I also tried mp.Queue()
inQ2 = mp.JoinableQueue()
qList = [inQ1, inQ2]
# set up bunches
bunches = []
for startFrame in range(0, fileLen, int(fileLen / processCount)):
endFrame = startFrame + int(fileLen / processCount)
bunches.append((startFrame, endFrame))
getFrames = []
for i in range(processCount):
getFrames.append(mp.Process(target=getFrame, args=(qList[i], bunches[i][0], bunches[i][1])))
for process in getFrames:
process.start()
results1 = [inQ1.get() for p in range(bunches[0][0], bunches[0][1])]
results2 = [inQ2.get() for p in range(bunches[1][0], bunches[1][1])]
inQ1.close()
inQ2.close()
for process in getFrames:
process.terminate()
process.join()
这篇关于如何使用cv2& amp;从视频并行获取帧python中的多处理的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!