[英]How to capture video in python with opencv and multithread (logitech c920)
[英]How to make python record 30 or 60 frames per second using openCV and a Logitech C920
我试图以 60 FPS 的速度录制 720p 或以 30 FPS 的 1080p 录制视频,但是在 python 上使用 C920 网络摄像头和 OpenCV 时,我只能在 720p 上获得大约 10 fps,在 1080p 上获得 5fps。
我为 openCV 尝试了很多不同的设置,但没有改变输出的 FPS。
import cv2
import time
FPS = 0
cap = cv2.VideoCapture(0)
fourcc = cv2.VideoWriter_fourcc(*'MJPG')
if(not cap.isOpened()):
exit()
cap.set(cv2.CAP_PROP_FOURCC, fourcc);
cap.open(cv2.CAP_ANY);
cap.set(cv2.CAP_PROP_CONVERT_RGB, 0);
cap.set(cv2.CAP_PROP_FRAME_WIDTH, 1280)
cap.set(cv2.CAP_PROP_FRAME_HEIGHT, 720)
cap.set(cv2.CAP_PROP_FPS, 60)
last = time.time()
for i in range(0,100):
before = time.time()
rval, frame = cap.read()
now = time.time()
print("cap.read() took: " + str(now - before))
if(now - last >= 1):
print(FPS)
last = now
FPS = 0
else:
FPS += 1
cap.release()
我希望它输出 60fps 但它只给出 9 或 10 fps
OpenCV自动选择第一个可用的捕获后端(请参阅此处) 。 可能是它没有自动使用V4L2。
如果从源代码构建,还应同时设置-D WITH_V4L=ON
和-D WITH_LIBV4L=ON
。
可能是由OpenCV选择的像素格式不支持所需的帧频,且所需的分辨率。 在Linux上,您可以使用v4l2-ctl --list-formats-ext
和v4l2-ctl --all
查看设置。
为了设置要使用的像素格式,请设置捕获的CAP_PROP_FOURCC
属性:
capture = cv2.VideoCapture(cam_id, cv2.CAP_V4L2)
capture.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('M', 'J', 'P', 'G'))
您可以使用cv2.VideoWriter()
。 这是函数头
cv2.VideoWriter([filename, fourcc, fps, frameSize[, isColor]])
例如将FPS设置为30
cv2.VideoWriter('output.avi', self.codec, 30, (frame_width, frame_height))
这是一个小部件,用于流式传输和记录网络摄像头中的帧。
from threading import Thread
import cv2
class WebcamRecordWidget(object):
def __init__(self, src=0):
# Create a VideoCapture object
self.capture = cv2.VideoCapture(src)
# 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('M','J','P','G')
self.output_video = cv2.VideoWriter('output.avi', 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)
# 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)
def save_frame(self):
# Save obtained frame into video output file
self.output_video.write(self.frame)
if __name__ == '__main__':
webcam_record_widget = WebcamRecordWidget()
while True:
try:
webcam_record_widget.show_frame()
webcam_record_widget.save_frame()
except AttributeError:
pass
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