找了一个高清USB摄像头查上去，识别是UVC Camera, 但是打开自带的Camera软件，并没有识别出来。打算从测试开始一步一步来看看是什么原因

1.摄像头识别检测和格式支持查询

查看设备节点，可见/dev/video9&10为摄像头节点，显示名称为Q8 HD Webcam: Q8 HD Webcam

[root@ok3568:/]# v4l2-ctl --list-devices
rkisp-statistics (platform: rkisp):
        /dev/video7
        /dev/video8

rkisp_mainpath (platform:rkisp-vir0):
        /dev/video0
        /dev/video1
        /dev/video2
        /dev/video3
        /dev/video4
        /dev/video5
        /dev/video6

Q8 HD Webcam: Q8 HD Webcam (usb-fd880000.usb-1):
        /dev/video9
        /dev/video10

查看摄像头支持的格式

[root@ok3568:/]# v4l2-ctl --list-formats-ext -d /dev/video9
ioctl: VIDIOC_ENUM_FMT
        Type: Video Capture

        [0]: 'MJPG' (Motion-JPEG, compressed)
                Size: Discrete 1920x1080
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 640x480
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 352x288
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 424x240
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 480x270
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 640x360
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 800x480
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 800x600
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 960x540
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 1024x576
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 1280x720
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 1600x896
                        Interval: Discrete 0.033s (30.000 fps)
        [1]: 'YUYV' (YUYV 4:2:2)
                Size: Discrete 1920x1080
                        Interval: Discrete 0.200s (5.000 fps)
                Size: Discrete 640x480
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 352x288
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 424x240
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 480x270
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 640x360
                        Interval: Discrete 0.033s (30.000 fps)
                Size: Discrete 800x480
                        Interval: Discrete 0.040s (25.000 fps)
                Size: Discrete 800x600
                        Interval: Discrete 0.067s (15.000 fps)
                Size: Discrete 960x540
                        Interval: Discrete 0.050s (20.000 fps)
                Size: Discrete 1024x576
                        Interval: Discrete 0.067s (15.000 fps)
                Size: Discrete 1280x720
                        Interval: Discrete 0.100s (10.000 fps)
                Size: Discrete 1600x896
                        Interval: Discrete 0.133s (7.500 fps)

2.摄像头采集格式查询和修改

摄像头采集格式查询

[root@ok3568:/]# v4l2-ctl -V -d /dev/video9
Format Video Capture:
        Width/Height      : 1920/1080
        Pixel Format      : 'MJPG' (Motion-JPEG)
        Field             : None
        Bytes per Line    : 0
        Size Image        : 4147200
        Colorspace        : sRGB
        Transfer Function : Default (maps to sRGB)
        YCbCr/HSV Encoding: Default (maps to ITU-R 601)
        Quantization      : Default (maps to Full Range)
        Flags             :

摄像头采集格式修改为YUYV格式，尺寸640*480

9
[root@ok3568:/]# v4l2-ctl -V -d /dev/video9
Format Video Capture:
        Width/Height      : 640/480
        Pixel Format      : 'YUYV' (YUYV 4:2:2)
        Field             : None
        Bytes per Line    : 1280
        Size Image        : 614400
        Colorspace        : sRGB
        Transfer Function : Default (maps to sRGB)
        YCbCr/HSV Encoding: Default (maps to ITU-R 601)
        Quantization      : Default (maps to Limited Range)
        Flags             :
[root@ok3568:/]#

3. 摄像头图像预览和拍照

摄像头图像预览

[root@ok3568:/]# gst-launch-1.0 v4l2src device=/dev/video9 !videoconvert !waylan
dsink
Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
WARNING: from element /GstPipeline:pipeline0/GstWaylandSink:waylandsink0: A lot of buffers are being dropped.
Additional debug info:
gstbasesink.c(2900): gst_base_sink_is_too_late (): /GstPipeline:pipeline0/GstWaylandSink:waylandsink0:
There may be a timestamping problem, or this computer is too slow.
WARNING: from element /GstPipeline:pipeline0/GstWaylandSink:waylandsink0: A lot of buffers are being dropped.
Additional debug info:
gstbasesink.c(2900): gst_base_sink_is_too_late (): /GstPipeline:pipeline0/GstWaylandSink:waylandsink0:
There may be a timestamping problem, or this computer is too slow.
WARNING: from element /GstPipeline:pipeline0/GstWaylandSink:waylandsink0: A lot of buffers are being dropped.
Additional debug info:
gstbasesink.c(2900): gst_base_sink_is_too_late (): /GstPipeline:pipeline0/GstWaylandSink:waylandsink0:
There may be a timestamping problem, or this computer is too slow.
WARNING: from element /GstPipeline:pipeline0/GstWaylandSink:waylandsink0: A lot of buffers are being dropped.
Additional debug info:
gstbasesink.c(2900): gst_base_sink_is_too_late (): /GstPipeline:pipeline0/GstWaylandSink:waylandsink0:
There may be a timestamping problem, or this computer is too slow.
WARNING: from element /GstPipeline:pipeline0/GstWaylandSink:waylandsink0: A lot of buffers are being dropped.
Additional debug info: