來自 stackoverflow 的親愛的開發人員，祝您有美好的一天。我目前正在使用我的樹莓派上的 USB 網路攝像頭錄制實時視頻，代碼如下：
import cv2 as cv
import time
class CameraInst():
# Constructor...
def __init__(self):
cap = cv.VideoCapture(0) # Capture Video...
cap.set(cv.CAP_PROP_FOURCC, cv.VideoWriter_fourcc('M','J','P','G'))
cap.set(cv.CAP_PROP_FPS, 15)
cap.set(cv.CAP_PROP_FRAME_WIDTH, 1920)
cap.set(cv.CAP_PROP_FRAME_HEIGHT, 1080)
self.cap=cap
print("Aufnahme wird vorbereitet")
time.sleep(1)
def captureVideo(self):
# Capture
ret, self.frame = self.cap.read()
cv.moveWindow('frame',0,0)
cv.imshow('frame',self.frame)
def main():
cam1 = CameraInst()
while(True):
# Display the resulting frames...
cam1.captureVideo() # Live stream of video on screen...
if cv.waitKey(1) & 0xFF == ord('q'):
break
if __name__=='__main__':
main()
當我使用 cap.set(cv.CAP_PROP_FPS, 15) 函式并且我不知道我做錯了什么時，代碼不再起作用。
我收到以下錯誤：
[ WARN:0] global ../modules/videoio/src/cap_gstreamer.cpp (961) open OpenCV | GStreamer warning: Cannot query video position: status=0, value=-1, duration=-1
[ WARN:0] global ../modules/videoio/src/cap_gstreamer.cpp (1214) setProperty OpenCV | GStreamer warning: GStreamer: unhandled property
[ WARN:0] global ../modules/videoio/src/cap_gstreamer.cpp (1824) handleMessage OpenCV | GStreamer warning: Embedded video playback halted; module v4l2src0 reported: Internal data stream error.
[ WARN:0] global ../modules/videoio/src/cap_gstreamer.cpp (536) startPipeline OpenCV | GStreamer warning: unable to start pipeline
[ WARN:0] global ../modules/videoio/src/cap_gstreamer.cpp (1085) setProperty OpenCV | GStreamer warning: no pipeline
[ WARN:0] global ../modules/videoio/src/cap_gstreamer.cpp (1085) setProperty OpenCV | GStreamer warning: no pipeline
Aufnahme wird vorbereitet
Traceback (most recent call last):
File "/home/pi/Documents/RPV_Video_V8.py", line 45, in <module>
main()
File "/home/pi/Documents/RPV_Video_V8.py", line 40, in main
cam1.captureVideo() # Live stream of video on screen...
File "/home/pi/Documents/RPV_Video_V8.py", line 31, in captureVideo
cv.imshow('frame',self.frame)
cv2.error: OpenCV(4.5.1) ../modules/highgui/src/window.cpp:376: error: (-215:Assertion failed) size.width>0 && size.height>0 in function 'imshow'
事實并非如此，如果我洗掉 cap.set(cv.CAP_PROP_FPS, 15) 那么代碼可以正常作業，但是使用 YUYV 而不是 MJPG 的攝像機記錄。
uj5u.com熱心網友回復：
將CAP_PROP_FOURCC屬性設定為MJPG。
查看 Video Writer (yes) 檔案以獲取有關處理fourcc 值的詳細資訊。
cap.set(cv.CAP_PROP_FOURCC, cv.VideoWriter_fourcc(*"MJPG"))
.set()方法呼叫的順序很重要。試著把這個放在第一位。也許也CAP_PROP_FPS可以確定。
還要確保進行正確的錯誤處理。
cap = ...
assert cap.isOpened()
ret, self.frame = self.cap.read()
if not ret:
... # handle this
如果后端是 gstreamer，也許會改變它。
# Windows: CAP_DSHOW or CAP_MSMF
VideoCapture(..., apiPreference=cv.CAP_DSHOW)
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