RK3568评估板应用：Camera 多媒体开发（二）-rk3568性能相当于高通哪个

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三、使用v4l2-ctl抓图

media-ctl工具的操作是通过/dev/medio0等media设备，它所管理是media的拓扑结构中各个节点的format，大小，链接。

v4l2-ctl工具则是针对/dev/video0，/dev/video1等video设备，它在video设备上进行set_fmt，reqbuf，qbuf，dqbuf，stream_on，stream_off等一系列操作。

本文主要用v4l2-ctl进行采集帧数据，设置曝光、gain、VTS等v4l2_control。建议先查看v4l2-ctl的帮助文档。帮助文档内容比较多，分成很多个部分，我们比较关心的是其的streaming，vidcap。

帮助文档梗概如下：

[root@RK356X:~]# v4l2-ctl – 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

完整的帮助文档如下：

[root@RK356X:~]# v4l2-ctl –help-all 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-meta metadata format 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-subdev sub-device 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]

与streaming相关的参数如下：

[root@RK356X:~]# v4l2-ctl –help-streaming Video Streaming options: –stream-count <count> stream <count> buffers. The default is to keep streaming forever. This count does not include the number of initial skipped buffers as is passed by –stream-skip. –stream-skip <count> skip the first <count> buffers. The default is 0. –stream-sleep <count> sleep for 1 second every <count> buffers. If <count> is 0, then sleep forever right after streaming starts. The default i s -1 (never sleep). –stream-to <file> stream to this file. The default is to discard the data. If <file> is -, then the data is written to stdout and the –silent option is turned on automatically. –stream-to-hdr <file> stream to this file. Same as –stream-to, but each frame is prefixed by a header. Use for compressed data. –stream-to-host <hostname[:port]> stream to this host. The default port is 8362. –stream-lossless always use lossless video compression. –stream-poll use non-blocking mode and select() to stream.

与vidcap相关的参数如下：

[root@RK356X:~]# v4l2-ctl –help-vidcap Video Capture Formats options: –list-formats display supported video formats [VIDIOC_ENUM_FMT] –list-formats-ext display supported video formats including frame sizes and intervals –list-framesizes <f> list supported framesizes for pixelformat <f> [VIDIOC_ENUM_FRAMESIZES] pixelformat is the fourcc value as a string –list-frameintervals width=<w>, height=<h>, pixelformat=<f> list supported frame intervals for pixelformat <f> and the given width and height [VIDIOC_ENUM_FRAMEINTERVALS] pixelformat is the fourcc value as a string –list-fields list supported fields for the current format -V, –get-fmt-video query the video capture format [VIDIOC_G_FMT] -v, –set-fmt-video四、使用v4l2-ctl抓帧

示例一，抓取RKCIF输出的1帧NV12数据保存到/tmp/nv12.bin，分辨率为640×480。在保存数据前，先丢弃前面3帧（即前面3帧虽然返回给userspace，但不保存到文件）。

$ v4l2-ctl -d/dev/video0\ –set-fmt-video=width=640,height=480, pixelformat=NV12 \ –stream-mmap=3 \ –stream-skip=3 \ –stream-to=/tmp/nv12. bin \ –stream-count=1 \ –stream-poll

运行过程中有<<<<符号输出，表示进度。可以检查/tmp/nv12.bin文件大小，如果有数据表示抓取成功。

示例二，抓取RKISP输出的10帧NV12数据保存到/tmp/nv12.bin，分辨率为1920×1080。

$ v4l2-ctl -d /dev/video0 \ –set-selection=target=crop, top=0, left=0, width=1920,height=1080 \ –set-fmt-video=width=1920, height=1080, pixelformat=NV12 \ –stream-mmap=3 \ –stream-to=/tmp/nv12. bin \ –stream-count=10 \ –stream-poll

同样运行过程中有<<<<符号输出，表示进度。可以检查/tmp/nv12.bin文件大小，如果有数据表示抓取成功。

参数的说明:

-d，指定操作对象为/dev/video0设备。

–set-selection，指定对输入图像进行裁剪。特别是当RKISP1的前级大小发生变化时要保证selection不大于前级输出大小。RKCIF的裁剪则是通过–set-crop参数设置的

–set-fmt-video，指定了宽高及pxielformat(用FourCC表示)。NV12即用FourCC表示的pixelformat。

–stream-mmap，指定buffer的类型为mmap，即由kernel分配的物理连续的或经过iommu映射的buffer。

–stream-skip，指定丢弃(不保存到文件)前3帧

–stream-to，指定帧数据保存的文件路径

–stream-count，指定抓取的帧数，不包括–stream-skip丢弃的数量

–stream-poll，该选项指示v4l2-ctl采用异步IO，即在dqbuf前先用select等等帧数据完成，从而保证dqbuf不阻塞。否则dqbuf将会阻塞直到有数据帧到来

五、使用GStreamer

在Rockchip发布的LinuxSDK下，可以使用GStreamer预览Camera的图像、编码。使用v4l2src plugin即可从video device中获取图像。默认地，rkisp_3A_server也会随之启动调制(Tunning)，从而能够得到亮度、色彩正常的图像。

1.使用GStreamer显示图像

以下命令可以将Camera图像显示在屏幕上。

$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/lib/gstreamer-1.0 $ export XDG_RUNTIME_DIR=/tmp/.xdg $ gst-launch-1.0 v4l2src device=/dev/video0! \ video/x-raw, format=NV12,width=640,height=480, framerate=30/1 ! kmssink

运行正常的话，屏幕上会显示出摄像头图像。按ctrl+c结束程序即可退出。

2.GStreamer视频、图片编码

Linux SDK同时还带有硬件编码，如下命令可以将Camera数据流编码并保存成文件。

$ gst-launch-1.0 v4l2src device=/dev/video0 num-buffers=100 ! \ video/x-raw, format=NV12,width=640,height=480, framerate=30/1 ! \ videoconvert ! mpph264enc ! h264parse ! mp4mux ! \ filesink location=/tmp/h264.mp4

$ gst-launch-1.0 -v v4l2src device=/dev/video0 num-buffers=10 ! \ video/x-raw, format=NV12,width=640,height=480 ! mppjpegenc ! \ multifilesink location=/tmp/test%05d. jpg

3.无屏板子调试

Rockchip Linux SDK 提供了librkuvc.so，利用该接口可以将板子当作一个uvc camera使用， 通过usb otg与PC端相连接。

4.摄像头测试：qcamera

开发板上烧入Buildroot固件后，开机启动，桌面上就会显示qcamera图标，用鼠标点击后，就会出现摄像头图像：