OpenCV Python视频播放-如何为cv2.waitKey()设置正确的延迟 [英] OpenCV Python Video playback - How to set the right delay for cv2.waitKey()
问题描述
我使用以下代码捕获视频文件，将其翻转并保存.
I used the following code to capture a video file, flip it and save it.
#To save a Video File
import numpy as np
import cv2
cap = cv2.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv2.cv.CV_FOURCC(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
ret, frame = cap.read()
if ret==True:
frame = cv2.flip(frame,0)
# write the flipped frame
out.write(frame)
cv2.imshow('frame',frame)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
else:
break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
该程序将输出另存为output.avi
This program saves the output as output.avi
现在，要播放视频文件，我使用了以下程序
Now, to playback the video file I used the following program
#Playing Video from File
import numpy as np
import cv2
cap = cv2.VideoCapture('output.avi')
print cap.get(5) #to display frame rate of video
#print cap.get(cv2.cv.CV_CAP_PROP_FPS)
while(cap.isOpened()):
ret, frame = cap.read()
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) #convert to grayscale
cv2.imshow('frame',gray)
if cv2.waitKey(1) & 0xFF == ord('q'):
break
cap.release()
cv2.destroyAllWindows()
此程序播放从第一个程序保存的视频文件output.avi.关键是，该视频显示快进.因此，我尝试更改cv2.waitKey()的延迟值.当我放100时，视频看起来不错.我如何知道该放哪个值?它应该与帧速率有关吗?我检查了output.avi的帧速率(请参见第二个程序中的cap.get(5)行)，得到20.但是如果我将20用作cv2.waitKey()的延迟，则视频仍然太快.
This program plays the video file output.avi saved from the first program. The thing is, this video appears fast forward. So, I tried changing the delay value for cv2.waitKey(). The video looked fine when I put 100. How do I know which value to put there? Should it be related to the frame rate? I checked the frame rate of output.avi (see line cap.get(5) in second program) and got 20. But if I use 20 as delay for cv2.waitKey() the video is still too fast.
任何帮助将不胜感激.
