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。

[WARN:0] 全局 /home/nvidia/host/build_opencv/nv_opencv/modules/videoio/src/cap_gstreamer.cpp (933) 打开 OpenCV | GStreamer 警告：无法查询视频位置：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

[WARN: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] global /home/nvidia/host/build_opencv/nv_opencv/modules/videoio/src/cap_gstreamer.cpp (480) isPipelinePlaying OpenCV | GStreamer 警告：GStreamer：尚未创建管道 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。还要确保您已从源代码安装 OpenCV，而不是使用 pip，因为 Jetson Nano 和 Xavier 在您从 pip 安装 OpenCV 时会出现一些问题。

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()