1.v4l2-ctl 常用操作
# 安装V4l2工具包
$ sudo apt install v4l-utils
# 通过v4l2查看摄像头设备
$ sudo v4l2-ctl --list-devices
EP28WD (usb-fe380000.usb-1.3):
/dev/video0
/dev/video1
# 查看当前摄像头支持的视频压缩格式
$ sudo v4l2-ctl -d /dev/video0 --list-formats
ioctl: VIDIOC_ENUM_FMT
Index : 0
Type : Video Capture
Pixel Format: 'YUYV'
Name : YUYV 4:2:2
Index : 1
Type : Video Capture
Pixel Format: 'H264' (compressed)
Name : H.264
Index : 2
Type : Video Capture
Pixel Format: 'MJPG' (compressed)
Name : Motion-JPEG
# 查看摄像头所有参数
$ sudo v4l2-ctl -d /dev/video0 --all
Driver Info (not using libv4l2):
Driver name : uvcvideo
Card type : EP28WD
Bus info : usb-fe380000.usb-1.3
Driver version: 4.4.167
Capabilities : 0x84A00001
Video Capture
Streaming
Extended Pix Format
Device Capabilities
Device Caps : 0x04200001
Video Capture
Streaming
Extended Pix Format
Priority: 2
Video input : 0 (Camera 1: ok)
Format Video Capture:
Width/Height : 640/480
Pixel Format : 'YUYV'
Field : None
Bytes per Line : 1280
Size Image : 614400
Colorspace : Default
Transfer Function : Default
YCbCr Encoding : Default
Quantization : Default
Flags :
Crop Capability Video Capture:
Bounds : Left 0, Top 0, Width 640, Height 480
Default : Left 0, Top 0, Width 640, Height 480
Pixel Aspect: 1/1
Selection: crop_default, Left 0, Top 0, Width 640, Height 480
Selection: crop_bounds, Left 0, Top 0, Width 640, Height 480
Streaming Parameters Video Capture:
Capabilities : timeperframe
Frames per second: 25.000 (25/1)
Read buffers : 0
brightness (int) : min=-64 max=64 step=1 default=0 value=0
contrast (int) : min=0 max=64 step=1 default=36 value=36
saturation (int) : min=0 max=128 step=1 default=64 value=64
hue (int) : min=-40 max=40 step=1 default=0 value=0
white_balance_temperature_auto (bool) : default=1 value=1
gamma (int) : min=72 max=500 step=1 default=100 value=100
gain (int) : min=0 max=100 step=1 default=0 value=0
power_line_frequency (menu) : min=0 max=2 default=1 value=1
white_balance_temperature (int) : min=2800 max=6500 step=1 default=4600 value=4600 flags=inactive
sharpness (int) : min=0 max=6 step=1 default=3 value=3
backlight_compensation (int) : min=0 max=2 step=1 default=1 value=1
exposure_auto (menu) : min=0 max=3 default=3 value=3
exposure_absolute (int) : min=1 max=5000 step=1 default=157 value=157 flags=inactive
exposure_auto_priority (bool) : default=0 value=1
# 查看摄像头所支持的分辨率
sudo v4l2-ctl --list-framesizes=MJPG -d /dev/video0
ioctl: VIDIOC_ENUM_FRAMESIZES
Size: Discrete 640x480 # Width/Height
Size: Discrete 800x600
Size: Discrete 1280x720
Size: Discrete 1280x960
Size: Discrete 1920x1080
Size: Discrete 1600x1200
Size: Discrete 2048x1536
Size: Discrete 2592x1944
Size: Discrete 3264x2448
2.v4l2-ctl 命令
$ v4l2-ctl help
unknown arguments: help
General/Common options:
--all display all information available
-C, --get-ctrl=<ctrl>[,<ctrl>...]
get the value of the controls [VIDIOC_G_EXT_CTRLS]
-c, --set-ctrl=<ctrl>=<val>[,<ctrl>=<val>...]
set the value of the controls [VIDIOC_S_EXT_CTRLS]
-D, --info show driver info [VIDIOC_QUERYCAP]
-d, --device=<dev> use device <dev> instead of /dev/video0
if <dev> starts with a digit, then /dev/video<dev> is used
-e, --out-device=<dev> use device <dev> for output streams instead of the
default device as set with --device
if <dev> starts with a digit, then /dev/video<dev> is used
-h, --help display this help message
--help-all all options
--help-io input/output options
--help-misc miscellaneous options
--help-overlay overlay format options
--help-sdr SDR format options
--help-selection crop/selection options
--help-stds standards and other video timings options
--help-streaming streaming options
--help-tuner tuner/modulator options
--help-vbi VBI format options
--help-vidcap video capture format options
--help-vidout vidout output format options
--help-edid edid handling options
-k, --concise be more concise if possible.
-l, --list-ctrls display all controls and their values [VIDIOC_QUERYCTRL]
-L, --list-ctrls-menus
display all controls and their menus [VIDIOC_QUERYMENU]
-r, --subset=<ctrl>[,<offset>,<size>]+
the subset of the N-dimensional array to get/set for control <ctrl>,
for every dimension an (<offset>, <size>) tuple is given.
-w, --wrapper use the libv4l2 wrapper library.
--list-devices list all v4l devices
--log-status log the board status in the kernel log [VIDIOC_LOG_STATUS]
--get-priority query the current access priority [VIDIOC_G_PRIORITY]
--set-priority=<prio>
set the new access priority [VIDIOC_S_PRIORITY]
<prio> is 1 (background), 2 (interactive) or 3 (record)
--silent only set the result code, do not print any messages
--sleep=<secs> sleep <secs>, call QUERYCAP and close the file handle
--verbose turn on verbose ioctl status reporting
3.usb摄像头与video匹配
linux系统接上usb摄像头会出现/dev/video*设备，如果接多个摄像头，通过/dev/video*无法与真实摄像头一一对应。由于有的时候一个usb摄像头会产生两个或多个video(只有一个能拍照)，所以通过udev的rule规则也无法固定。这时可以通过/dev/v4l/by-id/路径的软链接固定。
$ ll /dev/v4l/by-id/
lrwxrwxrwx 1 root root 12 Sep 10 14:32 usb-Generic_HDR_CAMERA_200901010001-video-index0 -> ../../video0
lrwxrwxrwx 1 root root 12 Sep 10 14:32 usb-Generic_HDR_CAMERA_200901010001-video-index1 -> ../../video1
lrwxrwxrwx 1 root root 12 Sep 10 14:24 usb-USB3.0_Camera_8M_USB3.0_Camera_8M_SITN00000000001-video-index0 -> ../../video2
lrwxrwxrwx 1 root root 12 Sep 10 14:24 usb-USB3.0_Camera_8M_USB3.0_Camera_8M_SITN00000000001-video-index1 -> ../../video3
1.使用应用程序camorama
sudo apt-get install camorama
camorama
#如果使用Xshell进行ssh远程访问，会提醒安装Xmanager软件显示视频流
Xmanager是一个运行于MS Windows平台上的高性能的X window服务器。可以在本地PC上同时运行Unix/Linux和Windows图形应用程序。
Xmanager可以将PC变成X Windows工作站，它可以无缝拼接到UNIX 应用程序中。在UNIX/Linux和Windows网络环境中，Xmanager 是最好的连通解决方案。
2.使用应用程序茄子（cheese）
cheese是Ubuntu自带摄像软件，中文名称茄子。
cheese + 设备号
sudo apt-get install cheese
cheese
# 或
cheese /dev/video0
#不支持ssh远程显示
sudo apt-get install ffmpeg
sudo ffmpeg -i /dev/video0 -vframes 1 -s 640x480 -q:v 2 -f image2 /tmp/image6-vdieo0-test1.jpg
sudo ffmpeg -rtsp_transport tcp -i rtsp://192.168.1.19:554/mpeg4 \ # base
-vcodec copy -an -f flv rtmp://172.17.0.1/live/camera0 \ # stream
-flags +global_header -f stream_segment -segment_time 60 -segment_format_options movflags=+faststart -reset_timestamps 1 -vcodec copy -q:v 4 -an -r 24 -strftime 1 /data/tmpfs/camera/video/%s.flv \ # video
-r 2/1 -strftime 1 -y /data/tmpfs/camera/capture.jpg # capture
# 从ip摄像头推流
sudo ffmpeg -rtsp_transport tcp -i rtsp://admin:jiangxing123@10.56.0.17:554/h264/ch1/sub/av_stream -vcodec copy -an -f flv rtmp://10.55.2.185:1935/live/camera0
# 从视频文件推流
sudo ffmpeg -re -i record.flv -vcodec copy -an -f flv rtmp://10.55.2.185:1935/live/camera0
# 从usb摄像头推流
sudo ffmpeg -f video4linux2 -qscale 10 -r 12 -s 640x480 -i /dev/video0 -f flv rtmp://10.55.2.185:1935/live/camera0
# ==============test==============
sudo ffmpeg -rtsp_transport tcp -i rtsp://192.168.1.19:554/mpeg4 -f flv -c:v libx264 -an rtmp://10.55.2.185:1935/live/camera0
sudo ffmpeg -rtsp_transport tcp -i rtsp://192.168.1.19:554/mpeg4 -vcodec copy -an -f flv rtmp://10.55.2.185:1935/live/camera0
sudo ffmpeg -rtsp_transport tcp -i rtsp://192.168.1.19:554/mpeg4 -vcodec libx264 -crf 5 -acodec aac -f flv rtmp://10.55.2.185:1935/live/camera0
sudo ffmpeg -rtsp_transport tcp -i rtsp://192.168.1.19:554/mpeg4 -vcodec libx264 -acodec aac -f flv rtmp://10.55.2.185:1935/live/camera0
# install gstreamer
apt-get -y install libgstreamer1.0-0 gstreamer1.0-plugins-base gstreamer1.0-plugins-good gstreamer1.0-plugins-bad gstreamer1.0-plugins-ugly gstreamer1.0-libav gstreamer1.0-doc gstreamer1.0-tools gstreamer1.0-x gstreamer1.0-alsa gstreamer1.0-gl gstreamer1.0-gtk3 gstreamer1.0-qt5 gstreamer1.0-pulseaudio
# 连续拍照
gst-launch-1.0 --gst-debug-level=3 v4l2src device=/dev/video0 ! \
image/jpeg,width=1920,height=1080,framerate=30/1 ! \
multifilesink location=/data/tmpfs/capture1.jpg max-files=1 post-messages=true
# 单次拍照
gst-launch-1.0 v4l2src device=/dev/video0 num-buffers=1 ! image/jpeg,width=1920,height=1080 ! filesink location=/data/tmpfs/capture2.jpg
gst-launch-1.0 -e --gst-debug-level=3 rtspsrc location=rtsp://192.168.1.19:554/mpeg4 ! rtph264depay ! h264parse ! tee name=t \
t. ! queue ! avdec_h264 ! queue flush-on-eos=true ! videorate ! video/x-raw,framerate=5/1 ! jpegenc ! multifilesink post-messages=true location=/data/tmpfs/camera/capture.jpg max-files=1 \ # capture
t. ! queue ! flvmux streamable=true ! rtmpsink sync=false location=rtmp://172.17.0.1/live/camera0 \ # stream
t. ! queue ! splitmuxsink max-size-time=600000000000 location=/data/tmpfs/camera/video/%06d.mp4 # video
https://blog.gtwang.org/linux/imagemagick-image-watermarking-tutorial/
sudo apt-get install imagemagick
# 左下角
convert /data/tmpfs/capture.jpg -gravity SouthWest -pointsize 40 \
-stroke none -fill white -annotate +5+5 "`date "+%Y-%m-%d %H:%M:%S"`" \
-stroke none -fill white -annotate +5+70 "$text" /data/tmpfs/output.jpg
# 左上角
convert /data/tmpfs/capture.jpg -gravity NorthWest -pointsize 40 \
-stroke none -fill white -annotate +5+5 "`date "+%Y-%m-%d %H:%M:%S"`" \
-stroke '#40DCD7' -fill white -annotate +5+70 "$text" /data/tmpfs/output.jpg
# 有阴影的文字
convert /data/tmpfs/capture.jpg \
\( -background 'rgba(0, 0, 0, .5)' -fill white \
-font Helvetica -pointsize 60 \
label:"`date "+%Y-%m-%d %H:%M:%S"` " -splice 20x20 \
\) -gravity NorthWest -geometry +40+40 \
-composite /data/tmpfs/output2.jpg
# 使用中文字体
text="Hello"
text2="D10.08"
# font对应中文字体路径
convert /data/tmpfs/capture.jpg -font /usr/share/fonts/truetype/wqy/wqy-microhei.ttc -gravity NorthWest -pointsize 60 \
-stroke none -fill white -annotate +40+40 "`date "+%Y-%m-%d %H:%M:%S"`" \
-gravity NorthEast -pointsize 60 \
-stroke none -fill white -annotate +40+40 "$text2" \
-gravity SouthEast -pointsize 60 \
-stroke none -fill white -annotate +40+40 "$text" /data/tmpfs/output.jpg
图片方位
NorthWest、North、NorthEast、West、Center、East、SouthWest、South、SouthEast。安装中文字体
sudo apt install -y --force-yes --no-install-recommends fonts-wqy-microhei
sudo apt install -y --force-yes --no-install-recommends ttf-wqy-zenhei
# 查看中文字体路径
$ fc-list :lang=zh-cn
/usr/share/fonts/truetype/wqy/wqy-microhei.ttc: WenQuanYi Micro Hei,文泉驛微米黑,文泉驿微米黑:style=Regular
/usr/share/fonts/truetype/wqy/wqy-microhei.ttc: WenQuanYi Micro Hei Mono,文泉驛等寬微米黑,文泉