查看“Mjpg-streamer”的源代码

=查看摄像头数据=
==列出所有摄像头设备==
<syntaxhighlight lang="bash">
[root@imx6ull:~]# v4l2-ctl --list-devices
pxp (pxp_v4l2):
        /dev/video0

USB 2.0 Camera (usb-ci_hdrc.1-1.3):
        /dev/video1
</syntaxhighlight>
==查看摄像头详细信息==
<syntaxhighlight lang="bash">
[root@imx6ull:~]#  v4l2-ctl -L -d /dev/video1
                     brightness 0x00980900 (int)    : min=-255 max=255 step=1 default=0 value=0
                       contrast 0x00980901 (int)    : min=0 max=30 step=1 default=15 value=15
                     saturation 0x00980902 (int)    : min=0 max=127 step=1 default=30 value=30
                            hue 0x00980903 (int)    : min=-16000 max=16000 step=100 default=0 value=0
 white_balance_temperature_auto 0x0098090c (bool)   : default=1 value=1
                          gamma 0x00980910 (int)    : min=20 max=250 step=1 default=98 value=98
           power_line_frequency 0x00980918 (menu)   : min=0 max=2 default=1 value=1
                                0: Disabled
                                1: 50 Hz
                                2: 60 Hz
      white_balance_temperature 0x0098091a (int)    : min=2500 max=7000 step=1 default=5000 value=5000 flags=inactive
                      sharpness 0x0098091b (int)    : min=0 max=15 step=1 default=2 value=2
         backlight_compensation 0x0098091c (int)    : min=0 max=2 step=1 default=1 value=1
</syntaxhighlight>		 

==查看摄像头支持的像素格式和分辨率==
<syntaxhighlight lang="bash">		 
[root@imx6ull:~]# v4l2-ctl --list-formats-ext -d /dev/video1
ioctl: VIDIOC_ENUM_FMT
        Type: Video Capture

        [0]: 'YUYV' (YUYV 4:2:2)
                Size: Discrete 640x480
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 160x120
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 320x240
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 352x288
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 800x600
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 1280x720
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 1280x1024
                        Interval: Discrete 0.083s (12.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 1600x1200
                        Interval: Discrete 0.111s (9.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
        [1]: 'MJPG' (Motion-JPEG, compressed)
                Size: Discrete 640x480
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 160x120
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 320x240
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 352x288
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 800x600
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 1280x720
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 1280x1024
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.050s (20.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.100s (10.000 fps)
                        Interval: Discrete 0.200s (5.000 fps)

</syntaxhighlight>
=使用mjpg_streamer预览摄像头数据=
==查看开发板IP地址==
<syntaxhighlight lang="bash">
[root@imx6ull:~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:01:3F:2D:3E:4D
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

eth1      Link encap:Ethernet  HWaddr 00:01:1F:2D:3E:4D
          inet addr:192.168.1.21  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fdfd:3597:aa7a:0:201:1fff:fe2d:3e4d/64 Scope:Global
          inet6 addr: fe80::201:1fff:fe2d:3e4d/64 Scope:Link
          inet6 addr: fdfd:3597:aa7a::914/64 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:558 errors:0 dropped:0 overruns:0 frame:0
          TX packets:291 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:221870 (216.6 KiB)  TX bytes:29419 (28.7 KiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:7756 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7756 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:468263 (457.2 KiB)  TX bytes:468263 (457.2 KiB)
</syntaxhighlight>
==mjpg_streamer参数讲解==
:使用mjpg_streamer -h 查看帮助信息。
<syntaxhighlight lang="bash">
[root@imx6ull:~]# mjpg_streamer -h
-----------------------------------------------------------------------
Usage: mjpg_streamer
  -i | --input "<input-plugin.so> [parameters]"
  -o | --output "<output-plugin.so> [parameters]"
 [-h | --help ]........: display this help
 [-v | --version ].....: display version information
 [-b | --background]...: fork to the background, daemon mode
-----------------------------------------------------------------------
Example #1:
 To open an UVC webcam "/dev/video1" and stream it via HTTP:
  mjpg_streamer -i "input_uvc.so -d /dev/video1" -o "output_http.so"
-----------------------------------------------------------------------
Example #2:
 To open an UVC webcam and stream via HTTP port 8090:
  mjpg_streamer -i "input_uvc.so" -o "output_http.so -p 8090"
-----------------------------------------------------------------------
Example #3:
 To get help for a certain input plugin:
  mjpg_streamer -i "input_uvc.so --help"
-----------------------------------------------------------------------
In case the modules (=plugins) can not be found:
 * Set the default search path for the modules with:
   export LD_LIBRARY_PATH=/path/to/plugins,
 * or put the plugins into the "/lib/" or "/usr/lib" folder,
 * or instead of just providing the plugin file name, use a complete
   path and filename:
   mjpg_streamer -i "/path/to/modules/input_uvc.so"
-----------------------------------------------------------------------
</syntaxhighlight>
:得知mjpg_streamer后需要接-i和-o两个参数，再分别看这两个参数提供的不同so插件文件支持哪些选项。
:可选的-h查询帮助信息、-v查询版本信息、-b后台执行就不多介绍了。
:输入so插件包含：input_uvc.so、input_testpicture.so、(input_file.so、input_ptp2.so、input_http.so)
:输出so插件包含：output_http.so、(output_file.so、output_udp.so、output_rtsp.so、output_viewer.so)
:其中括号部分，我这个Buildroot的mjpg_streamer版本没有提供。

*参考页面 https://hceng.cn/2019/06/23/AM335X%E2%80%94%E2%80%94USB%E6%91%84%E5%83%8F%E5%A4%B4/#3-Web%E6%98%BE%E7%A4%BA
==执行mjpg_streamer获取摄像头数据==
:如下所示我们使用-i参数指定输入so插件类型为uvc类型，-d参数指定使用的摄像头设备为/dev/video1 ，-r参数指定输入分辨率为640x480 ，-q参数指定uvc数据质量为90，-n参数说明不要初始化Linux-UVC驱动程序的dynctrls，-o参数指定输出类型为http方式，-w指定网站目录为/usr/camera/web
 mjpg_streamer -i "/usr/lib/mjpg-streamer/input_uvc.so -d /dev/video1  -r 640x480 -f 30 -q 90 -n" -o "/usr/lib/mjpg-streamer/output_http.so -w /usr/share/mjpg-streamer/www/"

==浏览器打开并查看摄像头数据==
:如上所示我们的开发板IP地址为<code>192.168.1.21 </code>,让后我们使用电脑浏览器打开如下地址即可预览摄像头数据。
 192.168.1.21:8080