[英]Increasing the number of frames decreases the duration of video in opencv videowriter?
[英]How to start and stop saving video frames according to a trigger with OpenCV VideoWriter
我正在构建一个通过 RTSP 记录来自 IP 摄像机的帧的应用程序。
我的引擎负责将视频保存在 mp4 中,Opencv VideoWriter 运行良好。 我正在寻找的是创建一个 startRecord 和一个 stopRecord 类方法,它们将根据触发器分别开始和停止记录(它可能是我传递给线程的参数)。 有谁知道做这种事情的最好方法是什么?
这是我的课:
from threading import Thread
import cv2
import time
import multiprocessing
import threading
class RTSPVideoWriterObject(object):
def __init__(self, src=0):
# Create a VideoCapture object
self.capture = cv2.VideoCapture(src)
# Start the thread to read frames from the video stream
self.thread = Thread(target=self.update, args=())
self.thread.daemon = True
self.thread.start()
def update(self):
# Read the next frame from the stream in a different thread
while True:
if self.capture.isOpened():
(self.status, self.frame) = self.capture.read()
def endRecord(self):
self.capture.release()
self.output_video.release()
exit(1)
def startRecord(self,endRec):
self.frame_width = int(self.capture.get(3))
self.frame_height = int(self.capture.get(4))
self.codec = cv2.VideoWriter_fourcc(*'mp4v')
self.output_video = cv2.VideoWriter('fileOutput.mp4', self.codec, 30, (self.frame_width, self.frame_height))
while True:
try:
self.output_video.write(self.frame)
if endRec:
self.endRecord()
except AttributeError:
pass
if __name__ == '__main__':
rtsp_stream_link = 'rtsp://foo:192.5545....'
video_stream_widget = RTSPVideoWriterObject(rtsp_stream_link)
stop_threads = False
t1 = threading.Thread(target = video_stream_widget.startRecord, args =[stop_threads])
t1.start()
time.sleep(15)
stop_threads = True
正如您在主 I 阅读框架中看到的那样,并将它们存储在一个单独的线程中。 然后我开始记录(记录方法是无限循环,因此阻塞),然后在 15 秒后,我试图传递一个“stop_record”参数以正确停止记录。
部分代码来自Storing RTSP stream as video file with OpenCV VideoWriter
有人有想法吗? 我读了很多 OpenCV 对于多线程来说可能非常棘手
N。
不是将参数传递给线程,而是使用类中的内部标志来确定何时开始/停止记录。 触发器可以像按空格键开始/停止录制一样简单。 当按下空格键时,它会切换一个内部变量,将self.record
设为True
以开始录制,设为False
以停止录制。 具体来说,要检查何时按下空格键,您可以检查cv2.waitKey()
返回的键值是否为32
。 如果您想要基于任何其他键的触发器,请查看此帖子以确定键代码。 这是使用空格键开始/停止录制视频的快速示例:
from threading import Thread
import cv2
class RTSPVideoWriterObject(object):
def __init__(self, src=0):
# Create a VideoCapture object
self.capture = cv2.VideoCapture(src)
self.record = True
# Default resolutions of the frame are obtained (system dependent)
self.frame_width = int(self.capture.get(3))
self.frame_height = int(self.capture.get(4))
# Set up codec and output video settings
self.codec = cv2.VideoWriter_fourcc(*'mp4v')
self.output_video = cv2.VideoWriter('output.mp4', self.codec, 30, (self.frame_width, self.frame_height))
# Start the thread to read frames from the video stream
self.thread = Thread(target=self.update, args=())
self.thread.daemon = True
self.thread.start()
def update(self):
# Read the next frame from the stream in a different thread
while True:
if self.capture.isOpened():
(self.status, self.frame) = self.capture.read()
def show_frame(self):
# Display frames in main program
if self.status:
cv2.imshow('frame', self.frame)
if self.record:
self.save_frame()
# Press Q on keyboard to stop recording
key = cv2.waitKey(1)
if key == ord('q'):
self.capture.release()
self.output_video.release()
cv2.destroyAllWindows()
exit(1)
# Press spacebar to start/stop recording
elif key == 32:
if self.record:
self.record = False
print('Stop recording')
else:
self.record = True
print('Start recording')
def save_frame(self):
# Save obtained frame into video output file
self.output_video.write(self.frame)
if __name__ == '__main__':
rtsp_stream_link = 'Your stream link!'
video_stream_widget = RTSPVideoWriterObject(rtsp_stream_link)
while True:
try:
video_stream_widget.show_frame()
except AttributeError:
pass
我通过在类中创建一个全局变量来解决这个问题,对于你的案例 endRec。
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