视频讲解

测试过程

读取摄像头窗口变大且很卡的代码

import cv2
cap = cv2.VideoCapture(0)
if not cap.isOpened():
    print("Cannot open camera")
    exit()
while True:
    ret, frame = cap.read()
    if not ret:
        print("no stream!")
        break
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()

运行后，读取摄像头的窗口很大，而且很卡，出现如下的提示

python3 test-camera.py
[ WARN:0@0.986] global /home/jetson/Downloads/opencv-4.5.5/modules/videoio/src/cap_gstreamer.cpp (1405) open OpenCV | GStreamer warning: Cannot query video position: status=0, value=-1, duration=-1
Gtk-Message: 21:12:47.677: Failed to load module "canberra-gtk-module"

安装libcanberra-gtk-module

sudo apt-get install libcanberra-gtk-module

继续运行，还是很卡，WARN还在，修改代码如下，增加cv2.CAP_V4L2

v4l2（video for linux two）是Linux中内核提供给应用层访问音视频驱动的统一接口。v4l2中获取摄像头的能力的是通过ioctl函数的VIDIOC_QUERYCAP命令获取。

import cv2
cap = cv2.VideoCapture(0, cv2.CAP_V4L2)
if not cap.isOpened():
    print("Cannot open camera")
    exit()
while True:
    ret, frame = cap.read()
    if not ret:
        print("no stream!")
        break
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()