使用Python中的OpenCV检测从mp4视频中检测到的对象位置的时间戳

时间:2017-12-06 16:09:24

标签: python opencv

我正在尝试使用Python中的OpenCV检测来自mp4视频文件的对象。我能够检测到视频中的对象。

我想获取在视频文件中检测到对象的位置的时间戳,并将其写入文本文件。

到目前为止,这是我的代码:

import cv2

my_cascade = cv2.CascadeClassifier('toy.xml')

def detect(gray, frame):
    toys= my_cascade.detectMultiScale(gray, 1.3, 5)
    for (x, y, w, h) in toys:
        cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
        #Logic to write time stamp to file goes here
    return frame 

video_capture = cv2.VideoCapture('home.mp4')
cv2.startWindowThread()
while True: 
    _, frame = video_capture.read() 
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) 
    canvas = detect(gray, frame) 
    cv2.imshow('Video', canvas) 
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
video_capture.release()
cv2.destroyAllWindows()

我尝试使用VideoCapture的方法get()使用属性标识符,如下所示:

 video_capture.get(CV_CAP_PROP_POS_MSEC)

但是出现错误 name' CV_CAP_PROP_POS_MSEC'未定义

似乎cv2没有实现此方法或属性标识符。

cv2中还有其他方法可以实现我想要的吗?

请帮忙。

解决

每次在视频中检测到对象时,都会打印对象位置的时间戳。 这是工作代码:

import cv2

my_cascade = cv2.CascadeClassifier('toy.xml')

def detect(gray, frame):
    toys= my_cascade.detectMultiScale(gray, 1.3, 5)
    for (x, y, w, h) in toys:
        cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
        print("Toy Detected at: "+str(video_capture.get(cv2.CAP_PROP_POS_MSEC)))
    return frame 

video_capture = cv2.VideoCapture('home.mp4')
cv2.startWindowThread()
while True: 
    _, frame = video_capture.read() 
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) 
    canvas = detect(gray, frame) 
    cv2.imshow('Video', canvas) 
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
video_capture.release()
cv2.destroyAllWindows()

1 个答案:

答案 0 :(得分:2)

cv2确实已实现该属性,但需要使用全名。

这应该有效

import cv2

my_cascade = cv2.CascadeClassifier('toy.xml')

def detect(gray, frame):
    toys= my_cascade.detectMultiScale(gray, 1.3, 5)
    for (x, y, w, h) in toys:
        cv2.rectangle(frame, (x, y), (x+w, y+h), (255, 0, 0), 2)
        #Logic to write time stamp to file goes here
    return frame 

video_capture = cv2.VideoCapture('home.mp4')
cv2.startWindowThread()
while True: 
    _, frame = video_capture.read() 
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) 
    canvas = detect(gray, frame) 
    print (video_capture.get(cv2.CAP_PROP_POS_MSEC))
    cv2.imshow('Video', canvas) 
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
video_capture.release()
cv2.destroyAllWindows()

即。您希望实例video_capture的属性不是泛型类VideoCapture,并且属性名称以类cv2.为前缀。属性名称为CAP_PROP_POS_MSECCV_CAP_PROP_MSEC - 取决于OpenCV版本(请参阅Can't get VideoCapture property as the property identifier are not defined)。