摘要－针对ubantu20
sudo apt install v4l-utils
v4l2-ctl --list-devices
- cv2 install on ubantu20
```
针对ubantu20
sudo apt install v4l-utils
v4l2-ctl --list-devices
pip uninstall opencv-python
conda install pyqt
pip install opencv-python==4.1.2.30
```
(py38) itdb@ai:/opt/aisty/doc/aitools$ /opt/aisty/app/anaconda3/envs/py38/bin/python /opt/aisty/doc/aitools/case/face/04-tt.py VIDEOIO ERROR: V4L2: Could not obtain specifics of capture window. [ WARN:0] global /io/opencv/modules/videoio/src/cap_v4l.cpp (802) open VIDEOIO ERROR: V4L: can't open camera by index 1 /dev/video1 does not support memory mapping Traceback (most recent call last): File "/opt/aisty/doc/aitools/case/face/04-tt.py", line 18, in <module> img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) # 转换为灰度图 cv2.error: OpenCV(4.1.2) /io/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'
查看摄像头编号
v4l2-ctl --list-devices
(base) itdb@ai:~/Desktop$ find /lib/modules/ -name "*v4l2*.ko" /lib/modules/5.8.0-59-generic/kernel/drivers/media/v4l2-core/v4l2-dv-timings.ko /lib/modules/5.8.0-59-generic/kernel/drivers/media/v4l2-core/v4l2-flash-led-class.ko /lib/modules/5.8.0-59-generic/kernel/drivers/media/v4l2-core/v4l2-fwnode.ko /lib/modules/5.8.0-59-generic/kernel/drivers/media/v4l2-core/v4l2-mem2mem.ko /lib/modules/5.8.0-59-generic/kernel/drivers/media/i2c/adv7511-v4l2.ko /lib/modules/5.8.0-59-generic/kernel/drivers/media/common/v4l2-tpg/v4l2-tpg.ko /lib/modules/5.8.0-59-generic/kernel/drivers/media/common/videobuf2/videobuf2-v4l2.ko /lib/modules/5.8.0-43-generic/kernel/drivers/media/v4l2-core/v4l2-dv-timings.ko /lib/modules/5.8.0-43-generic/kernel/drivers/media/v4l2-core/v4l2-flash-led-class.ko /lib/modules/5.8.0-43-generic/kernel/drivers/media/v4l2-core/v4l2-fwnode.ko /lib/modules/5.8.0-43-generic/kernel/drivers/media/v4l2-core/v4l2-mem2mem.ko /lib/modules/5.8.0-43-generic/kernel/drivers/media/i2c/adv7511-v4l2.ko /lib/modules/5.8.0-43-generic/kernel/drivers/media/common/v4l2-tpg/v4l2-tpg.ko /lib/modules/5.8.0-43-generic/kernel/drivers/media/common/videobuf2/videobuf2-v4l2.ko /lib/modules/5.8.0-63-generic/kernel/drivers/media/v4l2-core/v4l2-dv-timings.ko /lib/modules/5.8.0-63-generic/kernel/drivers/media/v4l2-core/v4l2-flash-led-class.ko /lib/modules/5.8.0-63-generic/kernel/drivers/media/v4l2-core/v4l2-fwnode.ko /lib/modules/5.8.0-63-generic/kernel/drivers/media/v4l2-core/v4l2-mem2mem.ko /lib/modules/5.8.0-63-generic/kernel/drivers/media/i2c/adv7511-v4l2.ko /lib/modules/5.8.0-63-generic/kernel/drivers/media/common/v4l2-tpg/v4l2-tpg.ko /lib/modules/5.8.0-63-generic/kernel/drivers/media/common/videobuf2/videobuf2-v4l2.ko (base) itdb@ai:~/Desktop$ sudo apt-get install v4l2-ctl Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package v4l2-ctl (base) itdb@ai:~/Desktop$ v4l2-ctl --list-devices Command 'v4l2-ctl' not found, but can be installed with: sudo apt install v4l-utils (base) itdb@ai:~/Desktop$ sudo apt install v4l-utils Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: linux-headers-5.8.0-43-generic linux-hwe-5.8-headers-5.8.0-43 linux-image-5.8.0-43-generic linux-modules-5.8.0-43-generic linux-modules-extra-5.8.0-43-generic Use 'sudo apt autoremove' to remove them. The following additional packages will be installed: libv4l2rds0 The following NEW packages will be installed: libv4l2rds0 v4l-utils 0 upgraded, 2 newly installed, 0 to remove and 15 not upgraded. Need to get 602 kB of archives. After this operation, 2,274 kB of additional disk space will be used. Do you want to continue? [Y/n] Y Get:1 http://cn.archive.ubuntu.com/ubuntu focal/main amd64 libv4l2rds0 amd64 1.18.0-2build1 [15.8 kB] Get:2 http://cn.archive.ubuntu.com/ubuntu focal/universe amd64 v4l-utils amd64 1.18.0-2build1 [586 kB] Fetched 602 kB in 3s (180 kB/s) Selecting previously unselected package libv4l2rds0:amd64. (Reading database ... 252070 files and directories currently installed.) Preparing to unpack .../libv4l2rds0_1.18.0-2build1_amd64.deb ... Unpacking libv4l2rds0:amd64 (1.18.0-2build1) ... Selecting previously unselected package v4l-utils. Preparing to unpack .../v4l-utils_1.18.0-2build1_amd64.deb ... Unpacking v4l-utils (1.18.0-2build1) ... Setting up libv4l2rds0:amd64 (1.18.0-2build1) ... Setting up v4l-utils (1.18.0-2build1) ... Processing triggers for libc-bin (2.31-0ubuntu9.2) ... Processing triggers for man-db (2.9.1-1) ... (base) itdb@ai:~/Desktop$ v4l2-ctl --list-devices Synaptics RMI4 Touch Sensor (rmi4:rmi4-00.fn54): /dev/v4l-touch0 USB Camera: USB Camera (usb-0000:00:14.0-1): /dev/video2 /dev/video3 Integrated Camera: Integrated C (usb-0000:00:14.0-6): /dev/video0 /dev/video1
Integrated Camera 电脑集成摄像机的编号是0，1
外部插的USB摄像机编号是2，3
编号改为2，即可调用外部摄像头
# 摄像头 cap = cv2.VideoCapture(2)