无法在 Jetson Xavier 的 python 中使用 OpenCV 捕获视频

Question

我正在尝试读取 Jetson Xavier（ubuntu 18）上的相机图像。 我面临一个问题。 当我运行以下代码时，它会发出警告并给出黑色（完整）图像。

[警告：0] 全局 /home/nvidia/host/build_opencv/nv_opencv/modules/videoio/src/cap_gstreamer.cpp (933) 打开 OpenCV | GStreamer 警告：无法查询视频 position：状态=0，值=-1，持续时间=-1

cam=cv2.VideoCapture(0)
if cam.isOpened():
    grab,img = cam.read()
    if grab is True:
        cv2.imshow('sample image',img)
    else:
        print(f"Image not found")
else:
    print("Camera not openedd")
       

cv2.waitKey(0) # waits until a key is pressed
cv2.destroyAllWindows() # destroys the window showing image

如果我使用“dev/video0”来读取图像，即

cam=cv2.VideoCapture('dev/video0')

我收到未打开相机的警告和自定义错误消息

[警告：0] 全局 /home/nvidia/host/build_opencv/nv_opencv/modules/videoio/src/cap_gstreamer.cpp (711) 打开 OpenCV | GStreamer 警告：打开 bin 时出错：没有元素“dev” [WARN:0] 全局 /home/nvidia/host/build_opencv/nv_opencv/modules/videoio/src/cap_gstreamer.cpp (480) isPipelinePlaying OpenCV | GStreamer 警告：GStreamer：管道尚未创建相机未打开

然后我创建了 gstream 字符串并将其传递给视频捕获，如下所示。 字符串如下

gstr = 'varguscamerasrc ! video/x-raw(memory:NVMM), width=(int)1920, height=(int)1080, format=(string)NV12, framerate=(fraction)60/1 ! nvvidconv flip-method=0 ! video/x-raw, width=(int)1280, height=(int)720, format=(string)BGRx ! videoconvert ! video/x-raw, format=(string)BGR ! appsink'

cap = cv2.VideoCapture(gstr, cv2.CAP_GSTREAMER)

我收到以下错误

Error generated. /dvs/git/dirty/git-master_linux/multimedia/nvgstreamer/gst-nvarguscamera/gstnvarguscamerasrc.cpp, execute:645 No cameras available

(python3:15402): GStreamer-CRITICAL **: 19:08:54.835: gst_mini_object_set_qdata: assertion 'object != NULL' failed
[ WARN:0] global /home/nvidia/host/build_opencv/nv_opencv/modules/videoio/src/cap_gstreamer.cpp (933) open OpenCV | GStreamer warning: Cannot query video position: status=0, value=-1, duration=-1
Traceback (most recent call last):

我是jetson的新手，请指导我。 谢谢

Answer 1

你可以试试下面的代码。 Also make sure you have installed OpenCV from source not using pip because Jetson Nano and Xavier make some problems when you install OpenCV from pip.

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()

    # Our operations on the frame come here
    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    # Display the resulting frame
    cv2.imshow('frame',gray)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()