K230 linux UVC使用指南

概述

本文将讲解如何在k230开发板上使用USB摄像头。

UVC使用流程

以k230-canmv为例

连接设备

系统启动后，连接USB摄像头，系统会检测到USB设备插入，同时/dev目录下会生成两个/dev/video*设备文件，下面以/dev/video0和dev/video1为例

[root@canaan ~ ]#lsusb
Bus 001 Device 001: ID 1d6b:0002
Bus 002 Device 001: ID 1d6b:0002
[root@canaan ~ ]#[   45.053193] usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
[   46.049135] usb 1-1: new full-speed USB device number 3 using dwc2
[   46.261329] usb 1-1: not running at top speed; connect to a high speed hub
[   46.269490] usb 1-1: config 1 interface 1 altsetting 1 endpoint 0x84 has invalid maxpacket 1024, setting to 1023
[   46.279757] usb 1-1: config 1 interface 4 altsetting 0 endpoint 0x3 has invalid maxpacket 512, setting to 64
[   46.290402] usb 1-1: New USB device found, idVendor=0380, idProduct=2006, bcdDevice= 0.20
[   46.298651] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[   46.305838] usb 1-1: Product: FHD Camera
[   46.309790] usb 1-1: Manufacturer: ANYKA
[   46.313728] usb 1-1: SerialNumber: 12345
[   46.320244] uvcvideo: Unknown video format 35363248-0000-0010-8000-00aa00389b71
[   46.327669] uvcvideo: Found UVC 1.00 device FHD Camera (0380:2006)
[   46.342750] usbhid 1-1:1.4: couldn't find an input interrupt endpoint

[root@canaan ~ ]#lsusb
Bus 001 Device 001: ID 1d6b:0002
Bus 001 Device 003: ID 0380:2006
Bus 002 Device 001: ID 1d6b:0002
[root@canaan ~ ]#ls /dev/video*
/dev/video0  /dev/video1

检查设备状态

使用v4l2-ctl -d /dev/video0 --all命令查看摄像头信息

[root@canaan ~ ]#v4l2-ctl -d /dev/video0 --all
Driver Info:
        Driver name      : uvcvideo
        Card type        : FHD Camera: FHD Camera
        Bus info         : usb-91500000.usb-otg-1
        Driver version   : 5.10.4
        Capabilities     : 0x84a00001
                Video Capture
                Metadata Capture
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps      : 0x04200001
                Video Capture
                Streaming
                Extended Pix Format
Media Driver Info:
        Driver name      : uvcvideo
        Model            : FHD Camera: FHD Camera
        Serial           : 12345
        Bus info         : usb-91500000.usb-otg-1
        Media version    : 5.10.4
        Hardware revision: 0x00000020 (32)
        Driver version   : 5.10.4
Interface Info:
        ID               : 0x03000002
        Type             : V4L Video
Entity Info:
        ID               : 0x00000001 (1)
        Name             : FHD Camera: FHD Camera
        Function         : V4L2 I/O
        Flags         : default
        Pad 0x01000007   : 0: Sink
          Link 0x0200000d: from remote pad 0x100000a of entity 'Processing 2': Data, Enabled, Immutable
Priority: 2
Video input : 0 (Camera 1: ok)
Format Video Capture:
        Width/Height      : 1920/1080
        Pixel Format      : 'MJPG' (Motion-JPEG)
        Field             : None
        Bytes per Line    : 0
        Size Image        : 4147200
        Colorspace        : Default
        Transfer Function : Default (maps to Rec. 709)
        YCbCr/HSV Encoding: Default (maps to ITU-R 601)
        Quantization      : Default (maps to Full Range)
        Flags             :
Crop Capability Video Capture:
        Bounds      : Left 0, Top 0, Width 1920, Height 1080
        Default     : Left 0, Top 0, Width 1920, Height 1080
        Pixel Aspect: 1/1
Selection Video Capture: crop_default, Left 0, Top 0, Width 1920, Height 1080, Flags:
Selection Video Capture: crop_bounds, Left 0, Top 0, Width 1920, Height 1080, Flags:
Streaming Parameters Video Capture:
        Capabilities     : timeperframe
        Frames per second: 30.000 (30/1)
        Read buffers     : 0

使用v4l获取图像

使用v4l2-ctl --device /dev/video0 --stream-mmap --stream-to=video0-output.jpg --stream-count=1命令采集一张jpg图片

[root@canaan ~ ]#v4l2-ctl --device /dev/video0 --stream-mmap --stream-to=video0-
output.jpg --stream-count=1
<
[root@canaan ~ ]#ls -lh
total 222K
-rw-r--r--    1 root     root      221.7K Jan  1 00:11 video0-output.jpg

使用opencv获取图像

拷贝video_cap测试应用到文件系统中并执行，会生成一个test.jpg文件

[root@canaan ~ ]#./video_cap
[root@canaan ~ ]#ls
nfs        test.jpg   video_cap

video_cap可通过命令/opt/toolchain/Xuantie-900-gcc-linux-6.6.0-glibc-x86_64-V2.10.1/bin/riscv64-unknown-linux-gnu-g++ --sysroot=/path/to/k230_linux_sdk/output/k230_canmv_defconfig/host/riscv64-buildroot-linux-gnu/sysroot video_cap.cpp  -lopencv_videoio -lopencv_core -lopencv_imgcodecs -o video_cap来编译生成，video_cap.cpp源码如下：

#include "opencv2/opencv.hpp"
using namespace cv;

int main()
{
    VideoCapture capture(0);
    Mat frame;
    capture>>frame;
    imwrite("test.jpg", frame);
    return 0;
}

用户应用

1. 通过v4l接口去采集图像，具体请参考v4l用户编程API或v4l-utils源码

2. 通过opencv接口去采集图像，具体请参考opencv编程

参考连接

v4l-utils源码 : https://linuxtv.org/downloads/v4l-utils/